Ethanol Production from Acid Hydrolysate of Cassava Peels using Saccharomyces cerevisiae

Abstract

Economic feasibility of ethanol production can be enhanced if the fermentable sugars can beobtained from the acid hydrolysis of low-cost lignocellulosic wastes. Cassava peels are renewable, cheapand widely available wastes in tropical countries. The aim of this work was to study the ethanol productionfrom cassava peel hydrolysate prepared by dilute-acid hydrolysis. Sulfuric acid was found to be moreeffective acid for the degradation of cassava peels to fermentable sugars, compared to hydrochloric acidand acetic acid. Acid hydrolysate of cassava peels, comprised mainly of glucose, was obtained afterdilute-acid hydrolysis under optimum condition at 135 °C for 90 min. Neutralized hydrolysates containingreducing sugars and glucose ca 60.74 g/100g and 37.09 g/100g cassava peels, respectively, were used assubstrates for ethanol production. Cassava peel hydrolysates with high sugar concentration were used asthe substrates in the fermentation medium to evaluate the kinetic behavior of Saccharomyces cerevisiae(5019) during the fermentation. Experiments were conducted with using glucose semi-synthetic medium inshaking flasks. Glucose was consumed within 18 h of fermentation. The volumetric ethanol productivityof 0.51 g/l.h and ethanol yield of 0.43 g/g were achieved. When reducing sugars from hydrolysates wereused the fermentable sugars were consumed within 10 h. The volumetric ethanol productivity of 0.29 g/l.hand ethanol yield of 0.27 g/g were obtained. These results showed that diluted-acid hydrolysis of cassavapeels are promising substrates for use in ethanol production.

Keywords : Ethanol / Cassava Peels / Acid Hydrolysate / Fermentation