Achieving polyhydroxyalkanoate production from rubber wood waste using mixed microbial cultures and anaerobic-aerobic feeding regime

In the past few years, creating value-added products has become the best choice to pretreat biomass waste. For instance, the fermentable sugar obtained after pretreatment bioconversion into valuable bioproducts, biopolymer as a typical representative, has become a potential strategy. In particular, the production of biopolymer polyhydroxyalkanoate (PHA) by mixed microbial cultures in waste activated sludge can be regarded as a promising alternative to traditional petrochemical plastics. In this study, the enzymatic hydrolysate of rubber wood was utilized as substrate to explore the optimal process conditions for the accumulation of PHA under anaerobic-aerobic mode. The results showed that longer operation cycle (24 h), suitable anaerobic duration (3.5 h) and secondary feeding regimen (secondary addition without draining liquid) were more beneficial to PHA production. After accumulation, the highest PHA production, PHA storage yield (YPHA/S) and ratio to cell dry weight (CDW) reached 929.8 mg COD.L-1, 0.24 g COD/g COD and 0.31 g PHA/g CDW, respectively. The YPHA/S values were similar to the previous reported 0.22 ~ 0.24 g COD/g COD. The results demonstrated that the secondary feeding regimen was an effective approach to improve the production of PHA with rubber wood enzymatic hydrolysate as substrate.