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.