Utilization of swine wastewater as a feedstock for the production of polyhydroxyalkanoates by Azotobacter vinelandii UWD

Azotobacter vinelandii UWD produced 0.69 g·l^-1 poly(hydroxybutyrate-co-hydroxyvalerate, PHBV) with 7.9 mol% hydroxyvalerate (HV) from twofold-diluted swine wastewater (SW). When supplemented with 20 g·l^-1 glucose, twofold-diluted SW increased copolymer production by 8.6 times. When three organic acids (acetate, propionate and butyrate) present in SW were supplemented with 20 g·l^-1 glucose, PHBV production was comparable (5.5 g·l^-1) to that in the case of using twofold-diluted SW supplemented with 20 g·l^-1 glucose. However, the HV level (1.1-1.3 mol%) was very low. The component in SW contributing to copolymer production was found to be valerate. By 20 mM valerate 0.2 g·l^-1 PHBV with 44.6 mol% HV was produced. With 30 g·l^-1 glucose supplementation, 4.0 g·l^-1 PHBV with 22 mol% HV was produced. The optimal ratios of carbon to phosphorus (C:P) and to nitrogen (C:N) were 165:1 and 22:1, respectively.