Decanter cake waste as a renewable substrate for biobutanol production by Clostridium beijerinckii

The aim of this study was to determine if decanter cake waste from a palm oil mill could be used as a renewable substrate for biobutanol production. Decanter cake waste was first hydrolyzed to fermentable sugars by nitric acid and detoxified by activated-charcoal. The detoxified hydrolysate supplemented with whey protein and ammonium sulfate as cheap nitrogen sources, was used for butanol production by growing cells of Clostridium beijerinckii. The detoxified hydrolysate was also used as a co-substrate for direct conversion of butyric acid to butanol in a nitrogen-free medium. By these two steps, C. beijerinckii produced 3.42 g/L of butanol with a yield of 0.28 C-mol butanol/C-mol carbon in the first step and produced 6.94 g/L of butanol with a yield of 0.47 C-mol butanol/C-mol carbon in the second step. This study has showed that decanter cake waste could serve as a low-cost substrate for biobutanol production.     

The production of poly(3-hydroxybutyrate) [P(3HB)] by a newly isolated Bacillus sp. ST1C using liquid waste from biodiesel production

A newly isolated poly(3-hydroxybutyrate) [P(3HB)] producing strain, ST1C, was identified as Bacillus aryabhattai based on its morphological, biochemical and molecular characteristics. It synthesized and accumulated relatively high amounts of P(3HB). The aim of this work was to establish if it could convert an inexpensive liquid waste product from the production of biodiesel, biodiesel liquid waste (BLW), to P(3HB). Using a mineral salt medium (MSM) containing 2.0 % (v/v) glycerol present in the BLW and both normal batch and a draw and fill culture method, B. aryabhattai ST1C produced a maximum P(3HB) content and biomass concentration of 72.31 % dry cell weight (DCW) and 7.24 g/L, respectively, over a 24 h cultivation period in the draw and fill cultivation method. From 24 h to the end of cultivation at 72 h both the P(3HB) content and the biomass concentrations continuously reduced. Concentrations of glycerol in the BLW in this MSM above 3.0 % (v/v) or from pure glycerol (PG) or with an added NaCl concentration of greater than 3.0 % significantly reduced both the maximum P(3HB) content and the biomass concentrations.