Optimization of fermentation conditions for efficient ethanol production by Mucor hiemalis

Abstract

Abstract Background Mucor hiemalis is a dimorphic fungus that efficiently produces ethanol from different sugars; however, the yield of ethanol production highly depends on the fermentation conditions. Objective The conditions for obtaining a high ethanol production yield were optimized in this study. Materials and methods A response surface methodology was used to optimize pH, temperature, and time of ethanolic fermentation by M. hiemalis. Additionally, wheat flour was enzymatically hydrolyzed and the hydrolysate solution with high glucose concentration was fermented by the fungus. Results The optimum pH, temperature, and time were 5.5, 30°C, and 36 h, respectively. Maximum ethanol and glycerol yields were 0.48 and 0.06 g/g, respectively. The biomass yield was between 0.01 and 0.16 g/g of consumed glucose. The results showed that the fungus was able to produce ethanol in a medium containing 5.5% (v/v) ethanol, while higher ethanol concentration prevented further production of ethanol. Conclusion At the optimized conditions, the fungus was able to consume glucose with the concentration of 140 g/L and produce ethanol with a yield of 0.45 g/g, which was comparable to that by Saccharomyces cerevisiae.