Sustainable production of poly(3-hydroxybutyrate) by Bacillus megaterium ATCC 14581: Kinetic and stoichiometric parameters of fed-batch production, ultrasound-assisted recovery, and characterization

The growing demand for bio-based materials has stimulated the development of sustainable alternatives to conventional plastics, among which polyhydroxyalkanoates (PHAs) stand out due to their biodegradability and biocompatibility. In this context, the present study evaluated the production, recovery, and characterization of poly(3-hydroxybutyrate) [P(3HB)] synthesized by Bacillus megaterium ATCC 14581 using rice parboiling wastewater (RPW) and confectionery industry effluent (CIE) as agro-industrial substrates. P(3HB) production was carried out in a fed-batch bioreactor under controlled conditions employing two nitrogen-feeding strategies: continuous supplementation (Strategy I) and intermittent supplementation (Strategy II). The recovery of P(3HB) was investigated using ultrasound-assisted extraction, employing chloroform and 1,2-dichloroethane as solvents. The P(3HB) recovered under the selected conditions was characterized by Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and biodegradability assays. Strategy II showed superior performance, reaching a maximum biomass concentration of 6.48 g/L at 27 h and a P(3HB) accumulation of 2.35 g/L, corresponding to 67.74% of cell dry mass, at 21 h of cultivation. Ultrasound-assisted extraction resulted in recovery yields of 6.16% for chloroform. Biodegradation tests demonstrated mass losses exceeding 80% after 84 days under controlled conditions, confirming the environmentally favorable behavior of the biopolymer. Overall, the results demonstrate that agro-industrial residues can be successfully valorized as low-cost substrates for P(3HB) production and that ultrasound-assisted technology represents a promising alternative for polymer recovery.