Effects of substrate concentration on bioethanol production from oil palm empty fruit bunches with simultaneous saccharification and fermentation (SSF)

Oil palm empty fruit bunches (OPEFB) are industrial wastes generated from the processing of palm oil. OPEFB has the potential to be feedstock for bioethanol production due to its high cellulose content. In this paper, ethanol production is conducted with Simultaneous Saccharification and Fermentation (SSF) method, which combined hydrolysis (saccharification) and fermentation process simultaneously in one reactor to create a faster conversion time and minimize costs. The aim of the study was to determine the effect of substrate concentration on the growth of microorganisms and the yield of bioethanol produced through the SSF method. Pretreatment of OPEFB to decompose lignin is done by soaking it in alkaline solution. Hydrolysis is carried out enzymatically with cellulase enzyme within 48 hours in incubator shaker. The process is then followed by fermentation within 12 hours by adding Zymomonas mobilis inoculum. The research method was done experimentally with descriptive analysis, which included the effects of OPEFB substrate concentration (3%, 6%, 9%, 12%, 15%) on ethanol production. The result shows that the high concentrations of substrate in the medium increase the concentration of glucose, in which the highest concentration is 3.2 g/L. The higher the substrate loading resulted in lower hydrolysis yield and ethanol yield. The highest ethanol concentration is 0.25 g/L, obtained from fermenting 9% OPEFB loading in 3 hours.