Novel bioprocessing strategy for polyhydroxybutyrate production from agro-industrial effluents: A waste biorefinery

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Effective waste management is still a burning issue in the modern world due to the generation of more waste than that can be properly disposed off. In this scenario, waste biorefinery has shown tremendous potential to drive improved waste disposal through income generation. The research work presented in the thesis investigates bioprocessing strategies to recover a value-added product, polyhydroxybutyrate (PHB), from agro-industrial effluents under the waste biorefinery approach. Initially, the volatile fatty acid (VFA) production from rice mill effluent (RME) and brewery effluent (BE) was influenced by gobar gas plant sludge (GPS) and brewery anaerobic sludge (BAS) in an untreated state and pretreated under cyclic heat and acid shock regime to convert the effluent streams into media suitable for PHB production using acidogenic fermentation. The acidification of RME with pretreated gobar gas plant sludge at the optimized feed to microbe ratio led to enhanced total VFA content (TVFA) and degree of acidification of 2437±0.03 mg/L and 86±0.13 % compared to all other combinations. Acetate and butyrate were the major VFAs produced after the pretreatment of GPS, along with stable COD and acidic pH profiles. However, the fermentation of RME with pretreated BAS had an enhanced even to odd ratio of 20.97±0.08 mg/mg along with the highest acetate and butyrate yield compared to all other combinations. The improvement can positively affect polymer composition and property. Meanwhile, the untreated system had the upper hand regarding TVFA concentration compared to the pretreated system due to the negative effect of the pretreatment regime on different microbial communities in BAS. Therefore, pretreatment of anaerobic inoculum inhibited carbon sinks and enhanced even-numbered VFA production from RME, indicating its potential implications as a fermentation media for improved PHB production.
Supervisors: Das, Gopal and Deka, Deepmoni
Waste Biorefinery, Volatile Fatty Acid, Polyhydroxybutyrate, Activated Sludge, Acidogenic Fermentation, Aerobic Feeding Strategy, Rice Mill Effluent, Brewery Effluent