Ethanol production from durian (Durio zibethinus Murray) peels by Saccharomyces cerevisiae

Durian peel, a waste of durian (Durio zibethinus Murray) was used as a medium for ethanol production by hydrolysis with concentrations of H2SO4 2.0% (v/v) and reaction time of 30 min at 121 degrees C in an autoclave. The hydrolysate was used as a medium for ethanol fermentation. Yeast strains, inoculums level (%), initial pH of culture medium, incubation temperatures and concentrations of nitrogen, magnesium and potassium sources were determined to maximize ethanol production. Saccharomyces cerevisiae TISTR 5019 was found to be the most efficient ethanol producer among all others and the optimum conditions were 10% (v/v) of inoculum, pH 4.0, incubation at 35 degrees C, 0.5% (w/v) ammonium sulphate, 0.1% (w/v) magnesium sulphate and 0.1% (w/v) potassium phosphate with a high amount of 1.22% (v/v) ethanol at the second day of fermentation. The fermentation in reactor-5L by used of 3L H2SO4 hydrolysate of durian peels, optimum condition at high ethanol production and varying the impeller speed at 50, 100, 150 and 200 rpm for 7 days were found that 100 rpm for 1 day yielded the highest ethanol production at 9.81 g/L. The increase in agitation speed significantly increased the cell mass (p<0.01). The efficiency of ethanol production from durian peels by Saccharomyces cerevisiae TISTR 5019 using static fermentation, impeller speed at 100 rpm and impeller speed at 100 rpm for 1 day followed with static fermentation showed that 100 rpm and impeller speed at 100 rpm for 1 day followed with static fermentation yielded the highest ethanol concentration of 21.73 g/L and ethanol yield of 1.10 g ethanol/g sugar. These results showed that waste of durian peels was a useful substrate for ethanol production.