Polyhydroxyalkanoates production from effluent of hydrogen fermentation process by Cupriavidus sp. KKU38

Abstract

This study investigated the use of the residual sugar and volatile fatty acids (VFAs) in the effluent of the hydrogen production process to produce polyhydroxyalkanoates (PHAs) by Cupriavidus sp. KKU38 in batch fermentation. VFAs in the effluent were lactic, butyric, acetic and propionic acids with a total VFA concentration of 1725 mg/L. The C/N ratio of effluent was 100:2.5, which is defined as the excess carbon and limited nitrogen condition suitable for PHA production. The experiments were conducted in 250-mL Erlenmeyer flasks with a 100 mL working volume. The inoculum size was 30% (v/v) with the initial number of cells 10⁶ cells/mL. Residual sugars and acetic acid in the effluent were the major substrates used to produce PHAs while lactic and butyric acids in the effluent were used for biomass synthesis. The maximum PHA concentration and PHA content obtained were 0.85 g/L and 71.42% (w/w) of dry biomass weight, respectively. After fermentation, carbon oxygen demand (COD) in the effluent was reduced by up to 82.73%.

Keywords:

• effluent
• hydrogen fermentation process
• polyhydroxyalkanoates
• Cupriavidus sp. KKU38

Acknowledgements

The authors thank the Office of the Higher Education Commission, Thailand, for supporting P.S. by a grant funded under the program Strategic Scholarships for Frontier Research Network for the Joint Ph.D. Program Thai Doctoral Degree. A research fund was gratefully received from Fermentation Research Center for Value Added Agricultural Products, Khon Kaen University, Thailand, and the Higher Education Research Promotion and National Research University Project of Thailand, Office of the Higher Education Commission, through the Biofuels Research Cluster of Khon Kaen University.