Recent progress and challenges in cyanobacterial autotrophic production of polyhydroxybutyrate (PHB), a bioplastic

Plastic plays a crucial role in the household, industrial, and healthcare sectors and has become an integral part of human civilization. The non-biodegradable nature of plastic leads to severe environmental hazards. Therefore, an eco-friendly bioplastic such as polyhydroxybutyrate (PHB) has the potential to replace conventional plastics. PHB from bacteria is very expensive due to the use of costly sugar in the fermentation process. Photosynthetic prokaryotes, cyanobacteria can produce PHB intracellularly, store it as carbon and energy source using sunlight and CO2. Cyanobacterial PHB is of superior quality compared with other prokaryotes. Many wild-types and genetically modified cyanobacteria show PHB accumulation under optimized conditions on the lab-scale, but only a few studies had reported large-scale PHB production. This review has explored the advances in upstream and downstream processing strategies for PHB production from cyanobacteria. Challenges associated with process optimization and strain development for industrial-scale PHB production and commercialization of bioplastic have also been discussed here.