Characterization of polyhydroxybutyrate (PHB) sustainably produced by Alcaligenes faecalis utilizing lactic acid as a...

Biodegradable plastics, such as polyhydroxybutyrate (PHB) derived from the fermentation of sustainable substrates via biotechnological approaches have the potential to replace those from petrochemically derived sources. Lactic acid, a renewable and plentiful organic acid often considered waste, is one such carbon source, yet studies utilizing it as a substrate are limited as the relatively harsh conditions required for its exploitation are not compatible with microbial fermentation. Inspired by this challenge, this work seeks to optimize the PHB production using a lactic acid feedstock and Alcaligenes faecalis, isolated from sugarcane root rhizospheres. Culture optimization was conducted by using different carbon and nitrogen sources at varying concentrations. The significant intracellular PHB accumulation of up to 88 % (w/w) of the bacterial cell dry weight was attained using lactic acid and ammonium chloride. The key functional groups (CH₃ and CO) confirmed by FTIR and NMR, phase purity via XRD, melting temperature of 178.5 °C evaluated by DSC, and tensile modulus of 63.8 ± 3.7 MPa were exhibited by the microbially produced PHB similar to commercial PHB. It thus highlights the potential of lactic acid as a renewable carbon source for cost-effective industrial PHB production and the development of environmentally friendly bioplastics for food packaging and biomedical applications.