Palm kernel cake (PKC), a by-product of palm oil industry, contains glucose and mannose as hexose sugars. This study was performed to determine the feasibility of using PKC as a lignocellulosic substrate for biobutanol production by Clostridium saccharoperbutylacetonicum N1-4 in an acetone-butanol-ethanol (ABE) fermentation process. Moreover, the effect of tryptone-yeast extract-acetate (TYA) medium and P2 medium on biobutanol production was evaluated. Experimental results showed that butanol production of 3.05 g/L was obtained using mannose sugar, which was comparable to 3.61 g/L butanol production measured using glucose. Moreover, the maximum production of biobutanol (0.38 g/L) was obtained at a PKC concentration of 30%, indicating the possibility of PKC utilization in butanol production. ABE fermentation of PKC using distilled water, TYA medium, and P2 medium showed that the highest butanol production (0.26 g/L) with ABE production of 0.38 g/L was obtained when ABE fermentation was conducted in P2 medium.

Cunninghamella bainieri 2A1 is an oleaginous fungus whose lipid accumulation profile is significantly influenced by metal ion concentrations in growth medium. Mg2+, Fe3+, Mn2+ and Cu2+ were found to be the important elements affecting lipid accumulation in this fungus. This study employs a statistical method (Response Surface Methodology -RSM) to study the combined effects of Mg2+, Fe3+, Mn2+ and Cu2+ on lipid accumulation of C. baineri 2A1. Cultivation was carried out in 250 mL Erlenmeyer flasks containing 100 mL nitrogen limited medium at 30 degrees C and 250 rpm agitation for 120 h. A thirty-run central composite design experiment was employed to identify and optimize the significant factors. In addition to Mg2(+) and Fe3(+) which were shown to have significant effects on lipid accumulation, the interactions between Mg2+ and Cu2+, as well as the effect of Cu2+ in quadratic terms were also found to have significant effect on the process (p< 0.05). The highest amount of lipid obtained in this study was 39% g/g biomass with optimal levels of Mg2+, Fe3+ and Cu2+ at 5.00, 0.017 and 0.0005 g/L, respectively, while Mn2+ was omitted. A 32% increment in lipid yield was recorded, where the lipid content increased to 38%, compared to initial yield of 29% g/g biomass prior to optimization. In conclusion, Mg2+ and Fe3+ have significant positive effect on the lipid accumulation of this fungus, whereas Mn2+ and Cu2+ exert negative effects in combination.

In this study, response surface methodology (RSM) was applied to optimize and investigate the ability of yeast extract, CaCO3, MgSO4, and K2HPO4 to maximize biobutanol production by a novel local isolate of Clostridium acetobutylicum YM1. A central composite design was applied as the experimental design, and analysis of variance (ANOVA) was used to analyze the experimental data. A quadratic polynomial equation was obtained for biobutanol production by multiple regression analysis. ANOVA analysis showed that the model was significant (p < 0.0001), and the yeast extract, CaCO3, and MgSO4 concentrations had a significant effect on biobutanol production. However, K2HPO4 did not have a significant effect on biobutanol production. The estimated optimum combinations for biobutanol production using C. acetobutylicum YM1 were 2 g/L yeast extract, 6 g/L CaCO3, 0.1 g/L MgSO4, and 1.1 g/L K2HPO4. Subsequently, the model was validated through use of the estimated optimum conditions, which confirmed the model validity and 13.67 g/L of biobutanol was produced.