Optimization of Bioethanol Production from Molasses using Saccharomyces cerevisiae with Response Surface Method-Central Composite Design Approach

Abstract

Bioethanol is one of alternative energy sources produced by fermenting carbohydrate rich materials with microorganism, especially the yeast Saccharomyces cerevisiae. It can be produced from feedstock with high carbohydrate content such as sugary, starchy and lignocellulosic materials. Molasses is a sugar production byproduct that has high glucose and other simple sugar content and therefore it is easy to ferment compared to starch or lignocellulosic materials that require pretreatment before fermentation. In the present study, we determine the optimum condition that can produce the highest ethanol using response surface method-central composite design (RSM-CCD) approach. Yeast strain used in the present study was Fali yeast, which is a commercially available industrial bioethanol strain. The concentration of molasses used in the present study was 40% (w/v) and factors optimized in the present study were pH, agitation rate and fermentation time. Twenty experiments were run based on the RSM-CCD using batch method. The results of the present study showed that the optimum condition was achieved when the pH, agitation rate and time of fermentation were 2, 368 rpm and 104 hours respectively. The concentration of ethanol reached 10.12% (w/v) at the optimum condition based on the model obtained. Validation of the model showed that 10.02% of ethanol can be achieved when the optimum condition was applied in laboratory experiment, indicating a good agreement between the mathematical model and experimental result.