Bacterial synthesis of polyhydroxyalkanoates using dark fermentation effluents: Comparison between pure and enriched mixed cultures

Polyhydroxyalkanoates (PHAs) are naturally occurring biopolymeric materials synthesized by a wide group of microorganisms. PHAs are known for their use as bioplastics as they have similar physicochemical properties to those of conventional plastics. In the present scenario, PHAs are produced by mixed bacterial cultures or pure cultures using various types of substrates. The present study aimed at investigating the ability of bacteria isolated from an enriched mixed culture to produce PHAs using both synthetic wastewater and effluents collected from hydrogen-producing reactor as substrates. PHAs production was performed using both the enriched mixed culture and the isolated strain Serratia ureilytica under nitrogen limitation aiming to compare PHAs accumulation capacity. The use of enriched mixed culture and synthetic wastewater resulted in the highest PHAs accumulation, i.e. 54 +/- 3% dry cell weight (DCW). However, when S. ureilytica was used, PHAs accumulation decreased, i.e. 51 +/- 2% DCW with synthetic acids, and 31 +/- 2% DCW with effluents collected from hydrogen-producing reactor. Produced polymer contained the co-polymer with monomer composition of poly-3(hydroxybutyrate-co-hydroxyvalerate). Food waste as substrate contributes in reducing the production cost of both hydrogen as well as PHAs production embedded with waste valorization.