Polyhydroxyalkanoates (PHA) ::microbial synthesis of natural polyesters

Among materials emulating fossil plastics in functionality and processability, polyhydroxyalkanoates (PHA) stand out as the sole group that is completely integrated into nature’s closed loop material cycle. Being biobased, biosynthesized, biodegradable, home and industrial compostable, and biocompatible, PHA biopolymers outperform competing polymeric materials labelled with “bio” attributes claiming sustainability. PHA biopolymers exhibit versatile material characteristics mimicking fossil plastics and are the most auspicious candidates to replace established fossil plastics, resins, and fibers. Roughly 40% of all prokaryotic strains accumulate PHA biopolymers, and more than 150 different hydroxyalkanoate (HA) monomers that make up PHA biopolymers have been described, making PHA the most versatile family of biopolymers known to humankind. Commercially relevant PHA homo- and heteropolyesters include 3-hydroxybutyrate, 3-hydroxyvalerate, 3-hydroxyhexanoate, and 4-hydroxybutyrate monomers. However, numerous other PHA heteropolyesters having higher number of carbon atoms in the individual building blocks have been studied and found to have reasonably relevant functionalities. Furthermore, PHA biopolymers can also be used in numerous non-plastic applications such as being the source of optically pure chemicals or biologically active substances. Therefore, we currently stand only at the beginning of PHA discovery and industrialization. While reducing plastic pollution, greenhouse gas emissions and climate change are the current drivers for intensified exploration and commercialization of PHA biopolymers, they have a far greater role to play than just being exploited due to their renewable nature and intrinsic biodegradability which have also been reviewed here. As consumers, brand owners, converters, waste managers, and policy makers conceive and acknowledge the beneficial attributes of PHA biopolymers in this current wave of commercialization, the next wave consisting of PHA biopolymers for durable applications would irreversibly reduce fossil plastics use helping us to make a quantum leap in reducing plastic pollution, greenhouse gas emissions, and climate change-related to fossil plastics use