Enhancement of bioethanol production from tofu waste by engineered simultaneous saccharification and fermentation (SSF) using co-culture of mold and yeast

Abstract

Tofu waste is a potential raw material for producing bioethanol since it has 52,82 % carbohydrate content, among which 35,12 % is starch. Indonesia has approximately 315 tofu business units that produce 2,6 million tons of tofu per year, so the availability of tofu waste is abundant, and its current use is only for feed. The use of starch as the raw material of bioethanol needs two steps, namely saccharification and fermentation. Application of Simultaneous Saccharification and Fermentation (SSF) technique may reduce the processing time of bioethanol production from starchy materials. The SSF involves co-culture, namely aerobic molds (Aspergillus niger) that hydrolyze starch into sugar and facultative anaerobic yeasts (Saccharomyces cerevisiae) that ferment sugar into ethanol. The objectives of the study were to obtain a production technique of bioethanol from the starch of tofu waste, which has more productive and higher yield through Engineered SSF/ESSF (stop aeration at a particular time) technique using co-culture of mold and yeast and to compare it with Conventional SSF/CSSF (complete aeration) technique. ESSF produced bioethanol at 11.39 g/L with the product yield per substrate used (Yp/s) of 0.36 g/g. In comparison, CSSF produced bioethanol at 7.69 g/L with the Yp/s of 0.23 g/g. ESSF technology has been proved to be more productive and efficient than CSSF since it can increase bioethanol production and Yp/s of 1.5 and 1.6 times, respectively. The study results also prove that the starch from tofu waste can be utilized as media for bioethanol production.