Perspectives on the production, structural characteristics and potential applications of bioplastics derived from polyhydroxyalkanoates

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Title: Perspectives on the production, structural characteristics
and potential applications of bioplastics derived from
polyhydroxyalkanoates
Authors: Priscilla B.S. Albuquerque, Carolina B. Malafaia
PII: S0141-8130(17)33045-3
DOI: http://dx.doi.org/10.1016/j.ijbiomac.2017.09.026
Reference: BIOMAC 8201
To appear in: International Journal of Biological Macromolecules
Received date: 14-8-2017
Revised date: 6-9-2017
Accepted date: 12-9-2017
Please cite this article as: Priscilla B.S.Albuquerque, Carolina B.Malafaia,
Perspectives on the production, structural characteristics and potential applications of
bioplastics derived from polyhydroxyalkanoates, International Journal of Biological
Macromoleculeshttp://dx.doi.org/10.1016/j.ijbiomac.2017.09.026
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http://dx.doi.org/10.1016/j.ijbiomac.2017.09.026
http://dx.doi.org/10.1016/j.ijbiomac.2017.09.026
1 
 
Perspectives on the production, structural characteristics and potential applications of bioplastics 
derived from polyhydroxyalkanoates 
Priscilla B.S. Albuquerque1, Carolina B. Malafaia1* 
1Laboratório de Bioprocessos, Centro de Tecnologias Estratégicas do Nordeste (CETENE), Av. Prof. Luís 
Freire, 01, Cidade Universitária, 50740-540, Recife, PE, Brazil. 
(*)Corresponding author: carol08malafaia@hotmail.com, Phone: +55.81.33347200. 
Abstract 
 Since the last two decades, the use of synthetic materials has increased and become more frequent 
in this capitalist system. Polymers used as raw materials are usually disposed very rapidly and considered 
serious damages when they return to the environment. Because of this behaviour, there was an increasing 
in the global awareness by minimizing the waste generated, in addition to the scientific community concern 
for technological alternatives to solve this problem. Alternatively, biodegradable polymers are attracting 
special interest due to their inherent properties, which are similar to the ones of the conventional plastics. 
Bioplastics covers plastics made from renewable resources, including plastics that biodegrade under 
controlled conditions at the end of their use phase. Polyhydroxyalkanoates (PHAs) are polyesters composed 
of hydroxy acids, synthesized by a variety of microorganisms as intracellular carbon and energy storage. 
These environmentally friendly biopolymers have excellent potential in domestic, agricultural, industrial 
and medical field, however their production on a large scale is still limited. This review considered the most 
recent scientific publications on the production of bioplastics based on PHAs, their structural characteristics 
and the exploitation of different renewable sources of raw materials. In addition, there were also considered 
the main biotechnological applications of these biopolymers. 
Key-words: biodegradable plastics; biopolymers derivatives; P(3HB); poly(3-hydroxybutyrate)-co-(3-
hydroxyvalerate); sustainability. 
 
1. Introduction 
 Over the years, man has taken from nature both elements and products essential to his existence, 
trying to ensure comfort and a high quality of life. In the name of the well-being and development, the 
society has explored many raw materials and various products synthesized by living organisms present as 
structural constituents, being mostly of organic origin. Such products, namely biopolymers, are high 
molecular weight macromolecules classified according to the monomeric unit used and the structure of the 
2 
 
biopolymer formed; in addition, they can also be classified depending on their origin, including groups of 
proteins, polysaccharides, lipids/surfactants, polyphenols, and polyesters [1]. In this study, special attention 
will be given to polyesters, a class of biopolymers formed by ester linkages between molecules of organic 
acids and alcohol. For example, there are polylactates (PLAs), which are produced by chemical synthesis 
from lactic acid, and polyhydroxyalkanoates (PHAs), composed of hydroxyalkanoic acids and produced by 
microbial fermentation [2]. 
 Conventional synthetic polymers are produced from petroleum derivatives, a non-renewable 
natural resource with various environmental problems mainly associated to their difficult degradation. The 
industrial development of the second half of the twentieth century was deeply marked by the emergence of 
plastic polymers. Especially in the 1940s, the use of plastics has revolutionized the society due to their 
interesting properties, such as mechanical strength, lightness, flexibility, versatility, practicality, chemical 
inertia and durability, all of them attributed to a material of low cost and able to replace products and 
packaging from other materials, including paper, glass, and metals. At this point, plastics assumed a relevant 
position in society and became essential in our routine [3]. 
 Actually, plastics are considered the most widely used polymers in our daily life especially in 
packaging applications [4]. Data related to plastics reported that its annual production exceeded 300 million 
tons in 2015, representing trillions of dollars in terms of global economic returns [5]; in fact, 34 million 
tons of plastic wastes are generated each year throughout the world and 93% of them are disposed of in 
landfills and oceans [6]. 
 The use of plastic is diversified, including some industrial, domestic and environmental 
applications, varying from bottles, packaging, grocery bags, canned jars, paints, to blankets, carpets, 
toothbrushes, tires or holders for electrical components. It is possible to observe that plastics are present in 
almost all of the utensils of daily use; this application as fast circulation materials, associated with an 
inadequate disposal, has made one of its main characteristics - durability - the great cause of serious 
environmental damages [7]. 
 Biodegradable plastics are polymers that degrade completely to microbial attack in a short period 
of time, under appropriate environmental conditions. There are several biodegradable plastics commercially 
available, such as PHAs, PLAs, polyhydroxybutyrates [P(3HB)], and PGA, as well as several blends 
(mechanical mixtures of different plastics) marketed by different companies [8]. PHAs are a class of linear 
polyesters consisting of hydroxy acid monomers (HA) connected together by an ester bond and 
3 
 
accumulated by several microorganisms as a reserve of carbon and energy. They emerge as a promise 
alternative in the scenario of synthetic versus biodegradable polymers, however the high cost of production 
of its biopolymer is substantially more expensive than synthetic plastics. 
 This review work considers the production of PHAs from bacteria, their structural characteristics, 
the exploitation of different raw materials as renewable sources of inputs and the beginning of the use of 
bioplastics as a promising alternative for replace the synthetic polymers. The most recent scientific 
publications on the main biotechnological applications of these biopolymers, especially as packaging, were 
also considered here. 
2. Plastics x Bioplastics 
 Plastics are commonly find in urban centres, but also accumulated in all environments where man 
is present; a serious problem associated to its worldwide distribution occurs when the rainwater carries the 
plastics to streams and rivers, reaching the sea. In the oceans, they accumulate in large patches of partially 
degraded material and cause the death of many marine animals thatand waste frying oil as sustainable resources for the bioproduction of medium-chain-
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[81] R.A. Verlinden, D.J. Hill, M.A. Kenward, C.D. Williams, Z. Piotrowska-Seget, I.K. Radecka, 
Production of polyhydroxyalkanoates from waste frying oil by Cupriavidus necator, AMB 
Express. 1 (2011) 11. doi:10.1186/2191-0855-1-11. 
[82] P. Europe, What is plastic? Bio-based plastics, 01 Mars. (2017). 
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[84] J. Quillaguaman, H. Guzman, D. Van-Thuoc, R. Hatti-Kaul, Synthesis and production of 
polyhydroxyalkanoates by halophiles: Current potential and future prospects, Appl. Microbiol. 
Biotechnol. 85 (2010) 1687–1696. doi:10.1007/s00253-009-2397-6. 
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3722–3742. doi:10.3390/ijms10093722. 
[86] A. Shrivastav, H.-Y. Kim, Y.-R. Kim, Advances in the applications of polyhydroxyalkanoate 
nanoparticles for novel drug delivery system., Biomed Res. Int. 2013 (2013) 581684. 
doi:10.1155/2013/581684. 
[87] P. Slepicka, Z. Malá, S. Rimpelová, V. Svorcík, Antibacterial properties of modified 
biodegradable PHB non-woven fabric, Mater. Sci. Eng. C. 65 (2016) 364–368. 
doi:10.1016/j.msec.2016.04.052. 
[88] N. Peelman, P. Ragaert, B. De Meulenaer, D. Adons, R. Peeters, L. Cardon, F. Van Impe, F. 
Devlieghere, Application of bioplastics for food packaging, Trends Food Sci. Technol. 32 (2013) 
128–141. doi:10.1016/j.tifs.2013.06.003. 
[89] S.M. Martelli, J. Sabirova, F.M. Fakhoury, A. Dyzma, B. de Meyer, W. Soetaert, Obtention and 
characterization of poly(3-hydroxybutyricacid-co-hydroxyvaleric acid)/mcl-PHA based blends, 
LWT - Food Sci. Technol. 47 (2012) 386–392. doi:10.1016/j.lwt.2012.01.036. 
[90] J.-S. Yoon, W.-S. Lee, H.-J. Jin, I.-J. Chin, M.-N. Kim, J.-H. Go, Toughening of poly(3-
hydroxybutyrate) with poly(cis-1,4-isoprene), Eur. Polym. J. 35 (1999) 781–788. 
doi:10.1016/S0014-3057(98)00068-8. 
[91] M. Zhang, N.L. Thomas, Blending Polylactic Acid with Polyhydroxybutyrate: The Effect on 
Thermal, Mechanical, and Biodegradation Properties, Adv. Polym. Technol. 30 (2011) 67–79. 
doi:10.1002/adv. 
[92] A.P. Bonartsev, A.P. Boskhomodgiev, a. L. Iordanskii, G.A. Bonartseva, A. V. Rebrov, T.K. 
Makhina, V.L. Myshkina, S. a. Yakovlev, E. a. Filatova, E. a. Ivanov, D. V. Bagrov, G.E. Zaikov, 
Hydrolytic Degradation of Poly(3-hydroxybutyrate), Polylactide and their Derivatives: Kinetics, 
Crystallinity, and Surface Morphology, Mol. Cryst. Liq. Cryst. 556 (2012) 288–300. 
doi:10.1080/15421406.2012.635982. 
[93] A.R. Santos, B.M.P. Ferreira, E.A.R. Duek, H. Dolder, M.L.F. Wada, Use of blends 
bioabsorbable poly(L-lactic acid)/poly(hydroxybutyrate-co-hydroxyvalerate) as surfaces for Vero 
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cell culture, Brazilian J. Med. Biol. Res. 38 (2005) 1623–1632. doi:10.1590/S0100-
879X2005001100009. 
[94] G. Cheng, Z. Cai, L. Wang, Biocompatibility and biodegradation of poly ( hydroxybutyrate )/ 
poly ( ethylene glycol ) blend ® lms, 4 (2003) 1073–1078. 
[95] M. Öner, B. Ilhan, Fabrication of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) biocomposites 
with reinforcement by hydroxyapatite using extrusion processing, Mater. Sci. Eng. C. 65 (2016) 
19–26. doi:10.1016/j.msec.2016.04.024. 
[96] W. Cao, A. Wang, D. Jing, Y. Gong, N. Zhao, X. Zhang, Novel biodegradable films and scaffolds 
of chitosan blended with poly(3-hydroxybutyrate), J. Biomater. Sci. Polym. Ed. 16 (2005) 1379–
1394. 
[97] V. Levkane, S. Muizniece-Brasava, L. Dukalska, Pasteurization Effect To Quality of Salad With 
Meat in Mayonnaise, Foodbalt. 1 (2008) 69–73. 
[98] D.Z. Bucci, L.B.B. Tavares, I. Sell, PHB packaging for the storage of food products, Polym. Test. 
24 (2005) 564–571. doi:10.1016/j.polymertesting.2005.02.008. 
[99] S. Muizniece-Brasava, L. Dukalska, Impact of Biodegradable PHB Packaging Composite 
Materials on Dairy Product Quality Biodegrad ē jamo PHB iepakojuma kompoz ī tmateri ā lu 
ietekme uz piena produktu kvalit ā ti, Impact PHB Packag. Mater. Dairy Prod. Qual. 16 (2006) 
79–87. 
 
Figure Captions 
 
Fig. 1. Structure of PHA 
Fig. 2. General scheme of the metabolic route for PHA synthesis [24] 
Fig. 3. Overview of the several steps associated to obtain PHAs by microorganisms (C* = carbon) 
Fig. 4. Obtainment and biodegradation cycle of PHAs 
30 
 
 
Fig.1. Structure of PHA 
 
Fig. 2. General scheme of the metabolic route for PHA synthesis [24] 
 
Fig. 3. Overview of the several steps associated to obtain PHAs by microorganisms (C* = carbon) 
31 
 
 
 Fig. 4. Obtainment and biodegradation cycle of PHAs 
 
Table caption 
 
 
 
Table 1. PHA production from bacteria, their capacity for accumulating the polymer by using different 
carbon sources and the group that they belong. 
Group Microorganism Carbon source Culture mode Accumulating % Reference 
I 
 
 
C. necator 
Crude glycerol 
and rapeseed 
meal hydrolysates 
Fed-batch 55.6 [1] 
 Volatile fatty 
acids from olive 
mill wastewater 
Fed-batch 55 [2] 
Modified strains of 
C. necator 
Glucose Flask and fed-
batch 
59.3 – 77.4 [3] 
Pseudomonas 
fluorescencis 
Frying oil One-stage 
batch 
Two-stage 
batch 
Fed-batch 
33.7 
 
50.1 
 
55.34 
[4] 
Pseudomonas putida Mixture of 
glycerol and 
octanoate or fatty 
acids 
Flask 10 - 57 [5] 
Bacillus megaterium, 
Bacillus sp., and 
Lactococcus lactis 
Glycerol reagent 
grade, residual 
glycerol, palm 
oil, Jatropha oil, 
castor oil, waste 
Flask 45.04 - 86.69 [6] 
32 
 
frying oils, and 
whey 
Burkholderia 
sacchari LFM 
Glucose and 
hexanoic acid 
Fed-batch 78 [7] 
Pandoraea sp. Crude glycerol 
and propanoic 
acid or hexanoic 
acid 
Flask 49 – 63.6 [8] 
Halomonas TD01 
and its derivatives 
Glucose, sucrose, 
maltose, fructose 
and glycerol 
Flask 69 – 82 [9] 
Zobellella 
denitrifican MW1 
Glycerol Fed-batch 66.9 [10] 
II 
Azotobacter 
chroococcum 
Starch Fed-batch 46 
 
[11] 
Batch 73.9 
 
Recombinant E. coli 
 
Whey from 
cheese 
 
Fed-batch with 
oxygen 
limitation 
 
80 
Fed-batch 
without 
oxygen 
limitation 
57 
Mixed microbial cultures 
Acetic, propionic 
and/or butyric 
acid 
Batch with 
different pHs 
47.9 - 67 [12]confuse them with food [9]. In 2010, 
five plastic patches were known to cover more than 40% of the surface of the oceans or 25% of the terrestrial 
globe [10]. Although the technologies for recovering the plastic wastes have been improved in recent years, 
the emerging increase in the world population requires a higher demand for plastic production and 
eventually an increase in the amount of plastic wastes. The incineration of plastic wastes is particularly 
applied in developed countries, however, some environmental drawbacks can be encountered during this 
process, including high levels of CO2 emissions and a huge amount of ash and slag containing hazardous 
and toxic compounds [4]. 
 Because of the environmental damage, the global awareness of the society by minimizing plastic 
waste has been growing and gaining special attention in important environmental campaigns. On the other 
hand, the scientific community try to develop technological alternatives to solve this problem. The last two 
decades have been marked by a crescent interest in public and scientific communities about the use and 
development of biopolymers, which can be obtained from renewable sources, display the important 
characteristic of biodegradability, in addition to present the desired physicochemical properties of 
conventional synthetic plastics [3]. 
 At this point, it is essential to understand that not all plastics derived from renewable sources are 
biodegradable and that biodegradable plastics are not always derived from biopolymers, but sometimes 
produced from fossil resources. In order to avoid misinterpretations, it is important to distinguish the above-
4 
 
mentioned concepts. Many stakeholders use the general term bioplastic to describe both the biodegradable 
plastics and the plastics derived from renewable source, but the first one refers to end-of-life options while 
the other means plastics made from a renewable raw material source. Polyethylene and bio-based 
polyamide belongs to the second group [11], whilst natural or modified starch, PHAs, polyglycolate (PGA), 
PLAs, polysaccharides, collagen, and polyvinylalcohols (PVA) could be considered biodegradable plastic 
materials made from renewable sources, thus included in both of the groups [12–15]. 
 In packaging production, biopolymers are considered environment-friendly because they act as a 
sustainable way to replace non-biodegradable and non-renewable polymers. However, high production cost 
is a dilemma closely associated to bioplastics, especially due to the substrate used as carbon source, which 
can represent 40 % of the total cost [16]. Researches on the production of biopolymers from locally 
available and renewable carbon sources, such as maize, dairy effluent, and agroindustrial waste (which is 
important due to the non-adequate treatment of the waste and the low cost associated to it, as well as the 
development of new microorganism strains and more efficient techniques for polymer recovery) [15] 
become economically interesting and, therefore, should continue to be studied. 
 The packaging production has approximately 40% of the rate of polymers production, being half 
of this production destined for food packaging. In particular, for synthetic plastic packaging, there are 
limited disposal methods and this is generating a crescent global concern about the environmental damages 
and the depletion of natural resources caused by conventional plastic packaging that are non-biodegradable. 
In this way, it is necessary to find sustainable alternatives of production, use and disposal for the polymers 
in order to reduce the impact caused to the environment. The use of plastics with biodegradable 
characteristics can serve as a response to this issue, especially considering the volume of bioplastics 
altogether going to bottle applications and packaging nowadays, which is far greater than the average for 
plastics standards [3,17]. 
 
3. PHAs: 
3.1 PHA history 
 PHAs are naturally occurring aliphatic polyesters consisting of carbon, hydrogen, and oxygen, 
whose general structural formula is shown in Fig.1. Both the side chain composition (R) and the number of 
repeating units determine the identity of the monomeric unit [18]. They are accumulated by a wide variety 
of bacteria from intracellular reserve materials and produced by different substrates, including industrial 
5 
 
byproducts, fats and oils, lignocellulosic raw materials, agricultural and household waste materials, 
glycerol, sugars and wastewater [19]. PHAs are deposited in the cytoplasm of cells in the form of granules 
presenting the advantage of storing excess nutrients without affecting the physiological conditioning of the 
microorganism [20]. 
 The surface of the granule is surrounded by a membrane composed of phospholipids and proteins, 
principally PHAsins (PhaPs), a class of proteins able to influence both number and size of PHA granules. 
The stereospecificity of the biosynthetic enzymes guarantees the stereochemical configuration of R. 
Approximately 150 different hydroxyalkanoic acids are known to be incorporated into 
polyhydroxyalkanoates, with microbial species from over 90 genera being reported to accumulate these 
polyesters [21]. The monomers of hydroxy acids are often in the form of 3-hydroxyalkanoates (3-HAs), 4-
HAs or 5-HAs, with saturated and unsaturated chains containing or not aliphatic and aromatic groups [22]. 
 The almost infinite quantity of polyester combinations is possible due to the wide variety of 
radicals R, while the arrangement and the different types of monomers that compose the polymer chain rule 
their physicochemical properties. The production of PHA depends on the chemical nature of the carbon 
substrate used in the supplementation of the culture media, as well as the metabolic pathways that the 
microorganism possesses. At various stages of the metabolism, the microorganism can generate 
intermediates in the form of hydroxyacyl-CoA, which will be recognized and polymerized by the enzyme 
PHA synthase, a key-enzyme for PHA biosynthesis [23]. One can observe a general scheme for the 
formation process of PHAs by microorganisms in Fig. 2. 
 
 Based on the size of the monomers, PHAs can be divided into three groups: short chain-length 
monomers (SCLs), whose residues have 3 to 5 carbon atoms, medium chain-length monomers (MCLs), 
with residues from 6 to 15 carbon atoms, and long chain-length monomers (LCLs), with residues including 
more than 15 carbon atoms [25]. This difference is mainly due to the substrate specificity of the PHA 
synthase that can accept 3-hydroxyalkanoic acid of a certain range of carbon length [24,26]. 
 For example, PHA synthase of Alcaligenes eutrophus can polymerise 3HAs consisting of 3–5 
carbon atoms, whereas the one of Pseudomonas oleovorans can only accept 3HAs of 6–14 carbon atoms. 
Hybrid polymers comprising both SCLs and MCLs monomeric units also exist, such as poly(3-
hydroxybutyrate-co-3-hydroxyhexanoate). Monomers with various functional groups, such as halogen, 
6 
 
hydroxy, epoxy, cyano, carboxyl and esterified carboxyl groups on the chain have also been discovered in 
MCLs PHAs [21,24,27]. 
 SCLs present thermoplastic properties, while MCLs have elastomeric characteristics, and this 
difference rule their applications. In what concerns their different thermal and mechanical properties, SCLs 
are considered stiff and brittle with a high degree of crystallinity (60–80%), whereas MCLs is more flexible 
with low crystallinity (25%), low tensile strength, high elongation to break, low melting temperature and 
glass transition temperature below to room temperature [27]. Indeed, thermoplastic PHAs could be used as 
potential substitutes for conventional plastics derived from petroleum due to their biocompatibility and the 
positive impact of their renewable sources. When discarded, they can be deposited in landfillswithout 
interfering on the decomposition of other materials; also, they can be mixed with organic matter and used 
as fertilizers, besides the possibility of being recycled [8]. 
 Poly(3-hydroxybutyrate), or P(3HB), the most known and studied PHA, was also the first one to 
be discovered. In 1926, the microbiologist Maurice Lemoigne from the Pasteur Institute in Paris observed 
the anaerobically degradation of a bacillus similar to Bacillus megaterium, in addition to the excretion of 
3-hydroxybutirc acid by it. In 1958, Macrae and Wildinson observed that B. megaterium accumulated the 
polymer when the ratio glucose/nitrogen increased, while its degradation occurred under restriction 
conditions of carbon and energy [28,29]. 
 During the following 30 years, the interest in this polymer was restricted to researches about 
methods to estimate the content of the P(3HB) producers cells, and the best conditions for the culture of the 
microorganism; researches and patents for the production of PHAs through different processes started only 
in the 70's. The English company Imperial Chemical Industries (ICI) was the pioneer in the development 
of this type of work with the production of P(3HB) and the copolymer poly(3-hydroxybutyrate)-co-(3-
hydroxyvalerate) [P(3HB-co-HV)]. The production of this chemical derivative presented advantages when 
compared to the homopolymer P(3HB) due to better mechanical properties and the production by 
microorganisms through different carbon sources [30]. 
 P(3HB) is a brittle polymer with poor elasticity, high degree of crystallinity, and melting 
temperature around 180ºC. In order to improve these characteristics and expand their applications, several 
works are studying new combinations of monomers and some of them already reached better thermoplastic 
characteristics for PHA blends [31–35]. 
7 
 
 In what concerns PHAs composition, the presence of aromatic monomers can significantly change 
their physical properties, leading to new applications in medical, pharmaceutical and biotechnological fields 
[36]. For instance, the biocompatibility property observed in polyesters able them to be applied in the 
medical field mainly due to their non-toxicity; besides that, the degradation of P(3HB) produces 3-
hydroxybutyric acid, a normal human blood constituent. They can also be used as sutures, microcapsules 
for the controlled release of drugs for human and agricultural use (fertilizers and pesticides), prosthesis, 
bone plates, heart valves, surgical screens and screws, supports for fibroblasts culture, in addition to other 
therapeutic devices [17,37]. In the paint industry, P(3HB) was used on the development of environmentally 
friendly coatings paints as polymer bind [38]. There are many other applications, such as: disposable cups, 
plates and cutlery, Tetra Park covers, tubes for the production of vegetable seedlings, agrochemicals 
packaging, textile fibers, electronic equipment components, among others. The similarity between 
conventional plastics and PHAs, especially P(3HB), is close related to the almost same values of melting 
temperature, glass transition temperature, elasticity and high degree of crystallinity [15,39]. 
 
3.2 PHA production 
 The industrial PHA production is divided in several steps and could be observed in a summarized 
diagram shown in Fig. 3. The process starts with reactivation and adaptation of the bacterial cells that are 
induced to the growth through the culture in a complex nutrient medium without limiting nutrients, under 
constant stirring around 200 rpm and temperature of 30ºC (in average). The growing cells are transferred 
to a new culture with a larger volume of medium and similar composition to that used in the fermentation 
process. In order to increase the number of cells, the above mentioned step is repeated few times, being 
performed in fermenters with successively larger volumes and the same fermentation medium. It is 
important to guarantee the availability of macronutrients (Fe, B, Mo, Ni, Cu, Mn, Co, Zn, Mn and Ca salts), 
potassium phosphate or calcium phosphate as phosphorus source, and hydroxide ammonium as nitrogen 
source, as well as pH in equilibrium. This first fermentation step lasts around 16 hours at a basic pH with 
no PHA accumulation by the bacterium.[40]. 
 
 At the second step, PHA synthesis is induced by limiting the nutrients required for cell growth, 
for example phosphorus or nitrogen, whilst an excess carbon medium is provided. Several carbon sources 
can be used to produce different types of PHAs, including carbohydrates, mono, di or polysaccharides such 
8 
 
as glucose, sucrose, lactose, starch and lignocellulose; triglycerides, fatty acids, glycerol, animal fat, 
vegetable oils, frying oils and methanol residue from the biodiesel industry; and hydrocarbons such as 
methane and hydrocarbons derived from plastic wastes. At this step, satisfactory levels of oxygen must be 
guaranteed by controlling conditions such as stirring and aeration; it is necessary due to the aerobic 
fermentation process occurred, in which the concentration of oxygen dissolved in the medium directly 
influences the kinetic parameters [41,42]. 
 The carbon source provided at the beginning of the fermentation is depleted around 12 h and must 
be continuously added, keeping a constant concentration in the medium; the dissolved oxygen must also be 
kept constant, increasing the constant stirring and the aeration of the system. This step lasts around 14 h 
while the other nutrients in the medium, mainly phosphorus and nitrogen, are depleted, then raising the cell 
concentration. The depletion of nutrients and the abundant carbon source discontinue the cells growth, thus 
initiating the final fermentation step, in which polymer accumulation occurs. The accumulating step 
increases the polymer content into the cell to around 80 % [19,43,44]. 
 The transition between growth and accumulating steps could be easily observed. The nutrients 
depletion is associated with a spontaneous elevation of the pH of the medium and few hours later, the 
demand for oxygen decreases, decreasing the need for stirring and aeration; the rate of carbon source 
consumption also decreases and its addition must be reduced [45]. In addition, changes in cell morphology 
can be attributed to the polymer storage [46]. 
 At the end of the accumulation step, the cell enzyme complex must be deactivated rapidly because 
the bacterium is directed to consume the accumulated polymer when the carbon source is depleted. The 
deactivation is usually done by pasteurizing, raising the temperature around 80°C for 15 minutes. The 
fermented medium is then conducted to the extraction and purification steps, with disruption of the cells 
and elimination of the cell debris by solvents and other chemicals. These steps, known as downstream, 
contribute significantly to the increase in the production costs of the biopolymers [47]. 
 The most used cultivation form in laboratory is agitation-aeration in submerged fermentation, 
whose 40% of the production costs can be attributed to the downstream steps, and around 40% refer to the 
raw material used as carbon source (as already mentioned). In addition, most studies reported in the 
literature are limited either to liquid wastes or to liquid by-products [48–50]. In this context, solid-state 
fermentation (SSF) becomes an interesting alternative since it can decrease downstream steps and acts as a 
promising technology for waste valorisation through the bioconversion of organic wastes, such as 
9 
 
agroindustrial residues, used as either substrate or inert support. SSF shows sustainable characteristics in 
the bioconversion of solid wastes that have been proved to be able to give high efficiency in terms of 
product yields and productivities, low energy consumption, and solving disposal problems [51]. 
 In a world with a growing population,reutilization of agricultural residues, for example cassava 
bagasse, rice bran and cakes remaining from vegetable oil extraction, gains a potential importance for both 
socio-economic and environmental reasons. Furthermore, for products obtained by SSF processes, the 
manufacturing costs are further lowered in those cases in which it is possible to use the fermented solids 
directly, without the need for downstream processing steps. Thus, fermented solids containing PHAs are 
able for the preparation of composite materials of increased biodegradability [21]. 
 Some factors may contribute to increase the competitiveness of PHAs in the market, including the 
development of better strains, which allow obtaining high cellular concentrations, besides the accumulation 
of large amount of biopolymers from low cost substrates. In addition, one can also consider more efficient 
extraction and recovery processes associated to a few steps and less use of organic solvents. Thus, several 
studies have been developed aiming the growth of PHA-producing strains in renewable carbon sources and 
agroindustrial residues [50,52–54]. The use of genetically modified plants has also been reported as a 
promising strategy for the production of PHAs establishing a new carbon cycle using only light as a source 
of energy [55,56]. 
 At present, the major carbon sources for commercial PHA production are still food-based glucose 
and vegetable oils. The use of hydrocarbon from waste plastics is only exploited at the laboratory scale, but 
more research should be conducted to improve its yields and productivity. The most recent scientific 
literature report the use of waste streams from biorefinery, including lignocellulosic sugars and glycerol, as 
a promising alternative for sustainable production of PHAs. So far, no comprehensive cost-effective 
methods have been developed to fully harness fermentable sugars from lignocellulose. It is an innovative 
idea an integration of PHA production within a biorefinery, which may offset the cost of bioethanol by co-
production of value-added PHAs [41]. 
 Defined as a facility that integrates biomass conversion processes and equipment to produce fuels, 
power, and chemicals from biomass, the biorefinery industry usually has two routes to refine biomass, 
which results in different relative quantities of its products. The first is associated to carbohydrates, whilst 
the second is a thermochemical route via syngas, in which biomass is gasified into syngas and then used to 
synthesize liquid fuels. In a petroleum-based refinery, some of the refined petroleum is transformed into 
10 
 
chemical feedstocks, such as ethylene, propylene and terephthalic acid, which are used to synthesize 
polymers. Most of the conceptual biorefineries produce biofuels through refining biomass as the target 
products. Suitable polymers have not yet been identified as co-products, like in a petroleum-based refinery. 
Based on current developed technology, PHA could be a suitable candidate in a biorefinery [41]. 
 
4. PHAs producers 
 It is well known that the most important factor to effectively produce PHAs is a biopolymer 
producer; in a second manner, the substrate has a great impact in the costs for fabrication of PHAs. In recent 
years, hundreds of microorganisms possessing the ability to produce different types of PHAs have been 
studied. They are recognized in a wide range of gram-positive and gram-negative bacteria and in archea. 
Most of them can not be considered as the hosts in the industrial production because their ability to 
synthesize PHAs is insufficient [28]. 
 An excellent production of PHAs is close related to strains with high speeds of growth and 
production, the use of low cost substrates and the efficiency to convert substrate in product [57]. The 
manufacturing costs of production of PHAs are still high nowadays, being commonly related to the polymer 
extraction process. It is important that the producing strain must have the capacity to accumulate at least 
60% of its cellular mass in polymer [24]. 
 Bacteria that are used for the production of PHAs can be divided into two groups based on the 
culture conditions required for PHA synthesis. The first group of bacteria requires the limitation of an 
essential nutrient (nitrogen, oxygen, phosphorous, magnesium or sulphur) for the synthesis of PHA from 
an excess carbon source. Bacteria included in this group are Cupriavidus necator (previously called 
Ralstonia eutropha), Alcaligenes eutrophus, Protomonas extorquens, and Pseudomonas oleovorans. The 
second group of bacteria, including Alcaligenes latus, a mutant strain of Azotobacter vinelandii, and 
recombinant Escherichia coli, do not require nutrient limitation for PHA synthesis and can accumulate 
polymer during growth. These characteristics have to be taken into consideration while production of PHA 
[24]. 
 High productivity of PHA can be obtained by fed-batch or continuous fermentation. For fed-batch 
culture of bacteria belonging to the first group, a two-step cultivation method is commonly employed. A 
desired concentration of biomass is obtained without nutrient limitation in the first step after which an 
essential nutrient is kept in limiting concentration in the second step to allow efficient PHA synthesis. At 
11 
 
the nutrient limitation (second) step, the residual cell concentration, in this case the cell concentration minus 
the PHA concentration, remains almost constant and the cell mass increases only because of the intracellular 
accumulation of PHA. The amount accumulated for each different bacterium belonged to the first group 
depends on the limiting nutrient and the ratio of depletion during the second step. Then, a mixture of carbon 
source and a nutrient to be limited should be fed at an optimal ratio to produce PHA with high productivity 
[24]. 
 For fed-batch culture of bacteria belonging to the second group, a nutrient feeding strategy is 
important to obtain a high yield of PHAs since the synthesis is not dependent on nutrient limitation in these 
bacteria. Complex nitrogen sources such as fish peptone, yeast extract or corn steep liquor can be 
supplemented to enhance cell growth as well as polymer accumulation. Both cell growth and PHA 
accumulation need to be balanced to avoid incomplete accumulation of PHA or premature termination of 
fermentation at low cell concentration [24]. Table 1 shows some references for PHA production from 
bacteria, their capacity for accumulating the polymer by using different carbon sources and the group that 
each referred bacteria belong. It is important to observe that mixed microbial cultures could be belonged 
either to the first or the second group of PHA producers bacteria. 
 
 
 Cupriavidus necator is the most studied and most frequently used bacterium in industrial 
applications due to its ability to accumulate an expressive amount of P(3HB) at the end of the growth 
exponential step from different carbon sources, as one can confirm on the above-mentioned references in 
Table 1. The scientific literature previously mentioned it as R. eutropha Hydrogenomonas eutropha, A. 
eutrophus, and Wautersia eutropha, and its reclassification in 2004 as C. necator was a result of DNA–
DNA hybridization experiments and evaluation of phenotypic characteristics, DNA base ratios and 16S 
rRNA gene sequences [64]. 
 B. sacchari has been also reported as a potential PHAs producer. For example, Mendonça et al. 
(2014) evaluated in the cultivation of this species thirty different carbon sources as co-substrates to 
incorporate different monomers into PHAs. The highest P(3HB) concentration (51.5% of cell dry weight) 
was observed in the culture supplemented with hexanoic acid. The authors for the first time demonstrated 
the modulation of the composition of P(3HB-co-3HHx) using mixtures of carbohydrate and hexanoic acid 
as carbon sources.More recently, the same species was tested with glucose and hexanoic acid in a fed-
12 
 
batch fermentation and reached 78 % of accumulated polymer [61]. It was also revealed that bacteria belong 
to Methylobacterium species synthesized SCLs from methanol. Studies applying cultivations of 
Methylobacterium sp. GW2 using this carbon source as a nutrient supplement have demonstrated that this 
bacteria was capable to accumulate up to 40% of P(3HB) [66]. These authors reported that this strain 
produced copolyester poly-3-hydroxybutyrate-poly-3-hydroxyvalerate at 30 % content when valeric acid 
was supplied as an auxiliary carbon source to methanol. 
 It is important to highlight the use of genetically recombined strains to produce PHAs. Since the 
end of the 80s, the structural genes for three key enzymes for PHA biosynthesis in R. eutropha and A. 
eutrophus have been cloned, sequenced, and expressed in E. coli because it is known that the last species 
does not normally produce PHAs. Sequencing revealed high respective homologies (71–80%) between the 
species, suggesting that R. eutropha and A. eutrophus inherited their PHA genes by horizontal transfer from 
a common ancestor [67,68]. Nowadays, genetic engineering still works to introduce changes that enable 
the bacteria to produce biopolymers becoming the most promising host microorganisms for PHAs. So, the 
available comprehensive knowledge about its molecular genetics and physiology made E. coli the pioneer 
organisms in the research concerning PHAs biosynthesis [28]. 
 Among the species of the Pseudomonas genus, several of them have the ability to accumulate 
PHAs and, despite accumulating less intracellular amount when compared to the very studied C. necator, 
B. sacchari, and E. coli, can use a wide variety of substrates, such as alkanes and alkanoic acid, producing 
PHAs of MCLs type. An interesting work about a new secretion mechanism of PHAs in Alcanivorax 
borkumensis give us an information that PHAs could be deposit in the extracellular environment [69]. It is 
possible to consider that this finding opens new ways for scientists. The main disadvantage for intracellulary 
accumulation of this biopolymers is the cytoplasm capacity and downstream processing for PHAs recovery 
from biomass. Whereas, the extracellularly PHAs production is not limited by the cell space and does not 
need to apply any cell breakage procedures making this process less complex [28]. 
 
5. The manufacturing of PHAs 
 Biodegradable plastics became more interesting for industry and society around the 60s when they 
have captured attention due to their thermoplastic properties. Although patents were originally filed in the 
United States by J. N. Baptist in 1962, the first industrial production of PHAs did not occur until the 80s 
[67]. 
13 
 
 During the 70s, because of the petroleum crisis, a scientific movement aimed at discovering 
alternative sources of fossil fuel reserves was undertaken. In 1974, the occurrence of PHAs in chloroform 
extracts of activated sewage sludge showed the inclusion of heteropolymers such as hydroxyvalerate (3HV) 
and 3-hydroxyhexanoate (3HHx), in addition to the already known P(3HB). The first one heteropolymer 
had a lower melting point than P(3HB) and, unlike the homopolymer, was soluble in hot ethanol. After that, 
at least 11 short-chain 3-hydroxyacids were detected by gas-chromatographic analysis, the principal ones 
being 3HB and 3HV, in polymer extracted from marine sediments. Purified polymer extracted from 
monocultures of B. megaterium contained approximately 95% 3HB, 3% 3-hydroxyheptanoate, 2% 3-
hydroxyoctanoate, and trace amounts of three other 3-hydroxyacids. Subsequently, there were found PHAs 
containing C4, C6, and C8 components in sewage sludge [37,67,70–73] 
 Now focusing on the beginning of the industrial production of PHAs, in 1982 the English company 
ICI recognized the potential of P(3HB) as a substitute for petrochemical plastics and marketed it under the 
trade name Biopol® [8,67]. The German company Wella® started to market a shampoo in packages of 
Biopol® [20], however, despite to be environmental attractive, the high cost of production of Biopol® did 
not stimulate a great commercial success, producing around 50 tonnes/year. In 1992, the production 
increased to 300 tonnes/year and, after that, to 600 tonnes/year in 1993 (managed by Monsanto, formally 
Zeneca Bioproducts, successor of ICI). In 1995, the polymer cost was US$ 15.00/kg [74], however, the cost 
for industrial scale PHAs production tends to decrease by utilizing simple equipment, friendliness 
environment, and cost effective substrates, for instance the estimated production for 1Kg of bioplastic to 
2.82 euros obtained by Koller et al. (2007) working with whey lactose and Haloferax mediterranei as 
production strain [75]. 
. Monsanto started developing the process of P(3HB) and P(3HB-co-3HV) production in transgenic 
plants [8]. In 2001, Biopol® was sold by Monsanto to the American Metabolix, which continued to work 
on the production of P(3HB) and P(3HB-co-3HV) in genetically modified plants [20]. In 2004, the 
American Procter & Gamble (P&G®) produced a P(3HB) co-polymer with hydroxyhexanoate 
[P(3HB/HHx)]; obtained by fermentation using genetically modified microorganisms and glucose and 
vegetable oils as substrates, the co-polymer namely Nodax® presented superior physical properties when 
compared to the homopolymer. After that, P&G® licensed the Japanese company Kaneka Co for the 
production of Nodax® on an industrial scale. P(3HB) was also commercially exploited by W.R. Grace and 
Chimie Linz, which was succeeded by Biomer, located in Germany, on the production of the polymer from 
14 
 
bacteria in small scale bioreactors by using sucrose as carbon source. Mitsubishi Gas Chemical Company 
in Japan also produced P(3HB) from methanol under the name Biogreen® [8]. 
 It is important to highlight that the interest in PHAs declined with the declining in the price of 
petroleum at the beginning of the 21th century, however this tendency has reversed in recent years due to 
a further increase in the price of this fuel. Nowadays, PHAs are produced by many companies, such as Bio 
on (Italy), Biocycle PHB Industrial SA (Serrano, SP, Brazil), Tianan Biological Material Polyone, Ianjin 
Green Bioscience Co., Ltd., and Jiangsu Nantian Group (both of them from China), Metabolix® (Woburn, 
MA, USA), Procter & Gamble Co., Ltd. (Cincinnati, OH, USA), and Goodfellow Cambridge, Ltd. (UK) 
[17]. 
 In 2016, more than 75 % of the bioplastics production capacity worldwide was bio-based, durable 
plastics. This percentage will increase to almost 80 % in 2021. Production capacities of biodegradable 
plastics, such as PLA, PHAs, and starch blends, are also growing steadily from around 0.9 million tonnes 
in 2016 to almost 1.3 million tonnes in 2021. PHA production will almost quadruple by 2021 compared to 
2016, due to a ramp-up of capacities in Asia and the USA and the start-up of the first PHA plant in Europe 
[76]. 
 Different research efforts are dealing with the valorisation of wastes as sources for cultivating a 
range of bacteria with the purpose of obtaining PHA biopolymers with improved sustainability. For 
example, ongoing research deals with a new bacterial strain (Pandoraea sp.) isolated from Atlantic 
rainforest in Brazil for PHA production utilizing crude glycerol from biodiesel industry [52]. Other 
researchers are working on the production of PHAs in biorefineries associated with the production of sugar 
and ethanol by Burkholderia sp.[77–79]. A recent investigation reported an efficient multi-stage process 
for olive oil mill wastewater valorisation towards PHA and biogas production [49], while other works used 
wastes from the food industry, including fruit pomaces [80] and frying oil [59,80,81], as sustainable 
resources for the bioproduction ofPHAs by different strains, including Pseudomonas sp. and Cupriavidus 
sp.. 
 Very recently, the combination of techniques to produce a PHA co-monomer poly(3-
hydroxybutyrate-co-3-hydroxyhexanoate) with controlled monomer composition by B. sacchari was also 
investigated [61], and an extensive evaluation of the potential of Colombian native strains (B. megaterium, 
Bacillus sp., and Lactococcus lactis) for producing PHAs from inexpensive substrates, waste, or byproducts 
15 
 
from different industries (Jatropha oil, castor oil, waste frying oil, whey, and residual glycerol) was 
performed [55]. 
 With the results above mentioned, it is possible to observe that, even with the commercial and 
ambiental importances and the knowledgement directed to researches dealing with biopolymers, the 
demand for renewable raw materials for the production of bioplastics is still expensive and smaller when 
compared to the use of biomass for other industries (especially food and biofuels). The market associated 
to biopolymers is forecasted to grow rapidly in the next decades, but this growth will have only limited 
impact on the agricultural market overall. For instance, the annual global production capacity of bioplastics 
was about 4.2 million tonnes in 2016, which requires about 500,000 hectares of land and corresponds 
approximately to 0.01% of available arable land in the world [82]. 
 Bioplastics currently make up an insignificant portion of total world production of plastics. 
Commercial manufacturing processes are expensive, however reducing costs by increasing the scale of 
production or improving metabolic and genetic engineering may change the reality of the competitiveness 
between conventional plastics and bioplastics. These factors, when added to increasing oil prices, shortage 
of the reserves at an alarming rate and growing environmental awareness, may expand the market for 
bioplastics in the future. 
 
5.1 Potential applications of PHAs 
 Among various biodegradable polymers under researching and development, PHAs have attracted 
attention because of the wide chemical diversity of their radicals, which render to physical properties as 
good as the ones of conventional plastics. These biopolymers could vary from rigid and brittle plastics to 
soft, elastomers, rubbers and adhesives, depending on their monomer composition [20]. They are also 
insoluble in water, non-toxic, and biocompatible, in addition to present piezoelectric properties. Some PHA 
films exhibit gas barrier properties comparable to polyvinyl chloride and polyethylene terephthalate, with 
the advantage of being biodegradables [83,84]. 
 PHAs are degraded upon exposure to soil, compost, or marine sediment. P(3HB) can be 
biodegraded in both aerobic and anaerobic environments, without forming any toxic products, justifying 
the fact that the polymer biodegradability is an attractive characteristic that contributes to a sustainable 
economy. The process occurs by colonizing the PHA surface by bacteria or fungi that secrete a specific 
16 
 
enzyme, the extracellular depolymerase, degrading the polymer in primary monomeric units. The products 
from degradation are then absorbed and metabolized by the cellule [85]. 
 The rate of PHA biodegradation depends on factors such as: temperature, humidity, pH and 
nutrient supply; if factors associated specifically to the PHA are in consideration, it is possible to highlight 
composition, crystallinity, additives and surface area [37]. Fig. 4 represents the production and degradation 
cycle of PHAs. 
 
 
 Plants use sunlight, CO2 and water to produce carbohydrates through photosynthesis; these 
biomolecules are used as substrate in industrial processes for the production of PHAs, which are then 
manufactured as bioplastics. After use, bioplastics can be deposited in active microbial environments and 
their biodegradation will form CO2 and water, substrates to restart the cycle from photosynthesis. The 
advantages related to the use of PHAs consist mainly in saving this raw material and reducing the costs 
when the bioplastic is finally discarded. After the disposal, the recovered material can be taken back by the 
agriculture as certificate quality-compost with economical (and ecological) advantages [12]. 
 PHAs present applications in domestic, agricultural, industrial and mostly medical field [27,60], 
for example as nanoparticles for drug delivery and biocompatible porous implants [86], support 
scaffolds for tissue engineering [39], and anti-bacterial applications [87]. PHAs have considerable potential 
in the production of basic necessities, for instance packaging products. The first PHA consumer product 
was launched in April 1990 by Wella®, in Germany, that marketed shampoos in bottles of Biopol® 
manufactured from ICI [67]. 
 Packaging field is the biggest polymer processing industry with the food sector being its principal 
customer; in addition, data from 2016 reported that packaging remains the largest portions of application 
for bioplastics with almost 40 % (1.6 million tonnes) of the total bioplastics market. The data also confirms 
a decisive increase in the uptake of bioplastics materials in many other sectors, including consumer and 
household goods, furniture, spor, health and safety (22 %, 0.9 million tonnes), and applications in the 
automotive and transport sector (14 %, 0.6 million tonnes) and the construction and building sector (13 %, 
0.5 million tonnes), where technical performance polymers are being used. Furthermore, a recent market 
study published by European Bioplastics estimated that the global bioplastics production capacity is set to 
17 
 
increase from around 4.2 million tonnes in 2016 to approximately 6.1 million tonnes in 2021 (Bioplastics, 
2016). 
 Biodegradable materials are receiving growing attention as raw materials used for production of 
bioplastics in packaging field because they represent an efficient alternative for the plastic pollution. 
Service time of plastics is often short, so they end up mostly in landfills and stay there for over 100 years; 
when plastic products are discarded in incorrect places, they can end up clogging sewers and drains, thus 
polluting streets, beaches and scenery, having a very costly impact on waste management. Furthermore, the 
pollution is creating significant environmental and economic burdens since plastics deplete natural fuels 
and other natural resources. This idoneous solution is well reflected by the volume of bioplastics altogether 
going to packaging and bottle applications nowadays, which is far greater than the average for standard 
plastics [9,17]. 
 Focusing on the food industry, the use of bioplastics as packaging is subjected to different 
limitations, restricting their use up to this moment. Besides the high cost, the concerns on availability as 
well as on the use of land to produce bioplastics, there are major limitations on the functionality. Low 
barrier properties towards gasses and water, thermal instability, brittleness (due to high glass transition and 
melting temperatures), stiffness, and poor impact resistance are the main limiting factors for the application 
of PHAs as food packaging. In this context, the most recent literature dealing with this issue have 
investigated different strategies to increase barrier capacity and improve mechanical properties of 
bioplastics [88]. 
 PHA copolymers and blends are efficient alternatives to improve processability and mechanical 
properties by lowering the processing temperature and reducing the brittleness of PHAs based plastics. So 
far many PHA heteropolymers and blends have been proposed for food packaging [33,89], however a range 
of purposes could be enumerated for other blends, for example the improvement on the mechanical 
properties of a blend composed by P(3HB), poly (vinyl acetate) and poly(cis-1,4-isoprene) [90]. P(3HB)and P(3HBV) with PLA resulted in most immiscible blends with enhanced thermal stability, improved 
ductility and toughness [91], decreased degradation rate [92], and a better cell growth [93]. P(3HB) and 
poly(ethylene oxide) were used to cell growth of Chinese hamster lung cells [94]. Hydroxyapatite could be 
used as reinforce agent on the mechanical properties of PHAs [95]. Furthermore, P(3HB) blended with 
chitosan resulted in miscible blend with improved flexibility, thermal stability, tensile strength, and 
swelling capacity [96]. The impact of blends composed by P(3HB) and P(3HBV) with the natural anionic 
18 
 
polymers kappa-carrageenan and fucoidan was investigated in tissue engineering and cell culture 
applications [32]. 
 The impact of the bioplastic on the food product could be observed in several investigations: 
Levkane, Muizniece-Brasava, & Dukalska (2008) [97] evaluated the effect of pasteurization on a meat salad 
packed in conventional and biobased packaging and found that P(3HB) films could be successfully used to 
pack this type of food. Bucci, Tavares, & Sell (2005) [98] performed physical, mechanical (dynamic 
compression and impact resistance), sensorial and dimensional (dimensions, volumetric capacity, weight 
and thickness) tests and concluded that conventional plastic can be replaced by P(3HB) for packaging of 
mayonnaise, margarine and cream cheese. Similarly, Muizniece-brasava & Dukalska (2006) [99] stated 
that P(3HB) materials are suitable materials for storage of sour cream. 
 In fact, plastics are considered to be the most widely used polymers in our daily life especially in 
packaging applications. The annual production of petroleum based plastics exceeded 300 million tons in 
2015 [5]. Plastics are efficient materials in many applications and help to save resources and improve 
quality of life in many ways during their use phase. It is considered a general point of view that the plastics 
industry should continue to strive towards a more efficient use of all kinds of resources, irrespective of their 
origin, however the efforts allowing the development of tailored solutions for the packaging sector could 
be considered extremely relevant. PHAs are gaining attention among biodegradable polymers due to their 
promising properties such as high biodegradability in different environments, versatility, in addition to their 
good thermomechanical and barrier properties. Indeed, PHAs can be then formulated and processed for use 
in many applications. 
 
6. Conclusions 
 The use of renewable resources for the production of bioplastics is often associated with means of 
reducing the dependency of the plastics industry on fossil resources. In this sense, the increase in the price 
of oil, the political instability of relations between the main countries holding the world's large reserves and 
the global consensus about the importance of climate protection through the reduction of greenhouse gas 
emissions, particularly CO2, point out to a real possibility of exploiting new raw materials as renewable 
sources of inputs for the production of chemicals, such as the PHAs. 
 The use of PHAs as a substitute for petroleum-based plastics depends on the ability to produce 
polyesters at competitive costs, so the successful implementation of commercial production systems of 
19 
 
PHAs should cover the optimization of all aspects associated to growthing conditions and the extraction of 
the polymer. The most current scientific publications demonstrate the industrial concern for the use of new 
inputs, besides the reduction in the costs of bioplastics production and the constant awareness about the 
substitution of conventional plastics for the innovative biopolymers. 
 In what concerns the use of bioplastics, there are several studies investigating their applications, 
especially as food packaging, and demonstrating their positive effect on barrier, thermal and mechanical 
properties and directly on the food product. It is possible to conclude that the main focus for bioplastic 
packaging are short shelf life applications and dry products that do not require high oxygen and/or water 
vapour barrier. In addition, there are many recent studies questioning the ecological merits of bioplastics 
from a life cycle perspective. 
 
Conflict of interest 
 Authors declare that they have no conflict of interest. 
 
Acknowledgments 
 Priscilla B. S. Albuquerque and Carolina B. Malafaia express hers gratitude to the Fundação de 
Amparo à Ciência e Tecnologia do Estado de Pernambuco (FACEPE) and the Conselho Nacional de 
Desenvolvimento Científico e Tecnológico (CNPq) for financial support. The authors also acknowledge 
the Centro de Tecnologias Estratégicas do Nordeste (CETENE) for structural support. 
 
Funding 
 This study was funded by CNPq and FACEPE, the last one referred to the public announcement 
FACEPE 02/17 of the agreement between FACEPE and CETENE. 
 
Ethical approval 
 This article does not contain any studies with human participants or animals performed by any of 
the authors. 
 
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