Review: characterization polyhydroxybutyrate (PHB) production from Bacillus megaterium sp. microorganism for renewable plastics industry.

Polyhydroxybutyrate (PHB), a biodegradable biopolymer derived from microbes has been growing in popularity in light of the shift toward ecologically viable materials. Bacillus megaterium can produce large amounts of PHB, use a wide range of substrates (including biomass and industrial waste) and can adapt to several environmental conditions for growth and production. Bacillus megaterium shows strong potential for PHB production, achieving up to 78.4% yield (w/w), molecular weights of 200-800 kDa, and productivity up to 1.73 g/L·h^-1 in fed-batch systems. It can utilize low-cost substrates such as molasses, crude glycerol, and lignocellulosic hydrolysates. Compared to Cupriavidus necator, its feedstock flexibility allows production cost reductions of up to 30% per ton in some studies. This review assesses some of the most significant progress made in producing PHB using B. megaterium, including: physicochemical characterization; genetic modifications; substrate variability; and fermentation method. We highlight key fermentation strategies, genetic modifications, and substrate innovations that have improved PHB yield and economic viability. Limitations such as downstream recovery challenges and the need for optimized feedstock pretreatment are critically discussed. Overall, B. megaterium has significant potential for sustainable production of PHB from renewable resources, helping to continue the development of reasonably priced and environmentally friendly bioplastics.