Bioethanol production from sugarcane molasses by co-fermentation of Saccharomyces cerevisiae TA2 and Wickerhamomyces anomalus HCJ2F-19

Abstract

Purpose Co-culturing of stress-tolerant fermenting yeasts is a widely used method to improve bioethanol production from biomass enriched in fermentable sugars. This study aims to produce bioethanol from sugarcane molasses by simultaneous co-fermentation of S. cerevisiae isolate TA2 and W. anomalus isolate HCJ2F-19. Method Response surface methodology (RSM) based on the central composite design (CCD) was employed to optimize fermentation conditions, including mixing rate (110–150 rpm), temperature (25–35 oC), molasses concentration (25–35 obrix), and incubation time (36–72 h). The ethanol concentration was analyzed using HPLC equipped with a UV detector. Results The mono-culture, S. cerevisiae TA2 produces 17.2 g.L− 1 of ethanol, 0.33 g.g− 1 of ethanol yield, and 0.36 g.L− 1.h− 1 of productivity compared to W. anomalus HCJ2F which produces 14.5 g.L− 1, 0.30 g.g− 1 and 0.28 g.L− 1.h− 1 ethanol, ethanol yield, and productivity under laboratory conditions, respectively. In comparison to single cultures of S. cerevisiae TA2, and W. anomalus HCJ2F, the co-fermentation showed an increased ethanol yield of 29% and 53% compared to the single species fermentations, respectively. The results showed that the growth of W. anomalus HCJ2F-19 and S. cerevisiae TA2 was not influenced by each other during the co-fermentation process. The one variable at a time optimization (OVAT) demonstrated an ethanol concentration of 26.5 g.L− 1 with a specific yield and productivity of 0.46 g.g− 1, 0.55 g.L− 1.h− 1, respectively, at pH 5.5, 25 obrix, 48 h, 150 rpm, 30oC, 60:40 inoculum ratio, and 10% overall inoculum size. The maximum ethanol concentration of 35.5 g.L− 1 was obtained by co-fermentation using the RSM-CCD tool at 30 obrix, 30oC, 54 h, and 130 rpm. Conclusion The results suggested that the co-fermentation of S. cerevisiae TA2 and W. anomalus HCJ2F improves bioethanol production under optimum fermentation conditions.