Bioplastic Polyhydroxyalkanoate (PHA): Recent Advances in Modification and Medical Applications

Abstract

A wide variety of bacteria are found to be the tiny factories in the production of polyhydroxyalkanoate (PHA) biopolymer. PHA is the polyesters of 3-hydroxyalkanoic acids which occur in bacteria when the bacteria is subjected to nutrient limitation and simultaneously fed with an excess amount of carbon. This unfavorable condition forces the bacteria to store carbon in the form of resorbable cellular inclusions called PHA. Biosynthesized PHA has the ability to replace the currently feasible harmful petroleum based plastics to biobased plastics. PHA research is being focused mainly on two facts - bulk production of environment friendly low-cost PHA and functional group modification for multiple applications to mankind. Many companies are already producing PHA with highly tunable properties and are looking into economically feasible technologies for mass production of PHA. The core focus of PHA research includes a selection of potential PHA producers and low to zero cost carbon sources such as carbon containing wastages of household, farms and industries. This challenge of “trash to treasure” still remains to attain. Tunable properties of PHA have made them a more interesting biomaterial to blend with suitable biopolymers including bioactive compounds. Under precise physiological environment, PHA blends can deliver promising mechanical properties, acting as effective drug carriers and showing time bound degradation. Perhaps desirably tuned PHA may address many health issues including orthopedics - load bearing cartilage, artificial membranes for kidneys, heart and wound management. PHA has high immunotolerance, low toxicity and sustained biodegradability, which have attracted diverse scientist with many medical advancements such as bioabsorbable sutures and 3D structures. In the near future, it is expected to derive many smart auto controllable products from PHA such as microsphere, which could be utilised for a range of applications much more than just drug delivery. Furthermore, naturally produced hybrid PHA will be an interesting candidate as they possess essential properties for targeted applications without further artificial blending or incorporating any components.

Development and Characterization of Sustainable Composites from Bacterial Polyester Poly(3-Hydroxybutyrate-co-3-hydroxyhexanoate) and Almond Shell Flour by Reactive Extrusion with Oligomers of Lactic Acid

“…These composites consist on a polymeric matrix in which wood (or whatever lignocellulosic subproduct of the food industry or agroforestry) particles (from 10 to 60 wt %, depending on the manufacturing process) are embedded, leading to an appearance and surface finishing similar to natural wood. As many times, the lignocellulosic fillers are by-products from other sectors, they are cheap and do not increase the cost of the WPC; in addition, they come from natural resources and, subsequently, they represent a sustainable source for use in new and environmentally friendly materials [3][4][5]. These WPCs are already replacing the use of traditional woods in some applications, which is an important protection of forest resources.…”

“…These WPCs are already replacing the use of traditional woods in some applications, which is an important protection of forest resources. WPCs formulations have been optimized in sectors as important as automotive, outdoor furniture, interior design, railings, floors, coatings, decks, fences, pergolas, decking, and so on [3][4][5][6][7][8].…”

“…Finally, a new family of very promising polymers is that of bacterial polyesters which are generally referred to as polyhydroxyalkanoates PHAs. PHAs include more than 300 different polyesters and copolymers such as poly(3-hydroxybutyrate) (P3HB or just PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), among others [5,9].…”

Microalgae as Contributors to Produce Biopolymers

“…The ideal plasticizer needs to be biodegradable, nontoxic, and stable or nonvolatile [ 33 ]. Examples of common plasticizers are glycerol (considered as a conventional type of plasticizer for hydrophilic polymers [ 33 ], oxypropylated glycerin (or laprol), glycerol triacetate, polyethylene glycol, 4-nonylphenol, acetyl tributyl citrate, acetylsalicylic acid ester, salicylic ester, dioctyl phthalate, and dibutyl phthalate [ 49 ]. Behind the crystallinity and low cost, their physical and thermal properties are also of extreme importance.…”

“…It has been reported that the degradation rate of P(3HB) in P(3HB)/lignin blends can be reduced due to the formation of strong hydrogen bonds between lignin and P(3HB) [ 53 ]. The degradation rates of some immiscible binary blends such as P(3HB)/poly(propiolactone), P(3HB)/poly(ethylene adipate), and P(3HB)/P(3HB-co-3HV) were found to be higher than those of their pure counterparts due to their phase-separated structure [ 49 ].…”