Sustainable and optimized bioethanol production using mix microbial consortium of Saccharomyces cerevisiae and Candida cantarelli

Abstract

Agro-industrial wastes, the most abundant, readily available, and economical materials are of supreme interest that supports sustainable transformation into high-value fuels. However, the low productivity of ethanol due to the inhibition from the degradation product is a significant concern. In the present study, this limitation has been overcome by fermentation of pre-treated saccharified corn stover (CS) with co-cultures of locally isolated and identified strains, i.e., Saccharomyces cerevisiae (FBL-01) and Candida cantarelli (FBL-01). Three factor Box Behnken Design (BBD) and regression analysis was employed for optimum yield of ethanol. The lignin content in residual solids was decreased to 3.95%, although 91.28% of lignin was decomposed in CS after pre-treatment with 1% (w/v) NaOH. HPLC analysis revealed that concentration of reducing sugars; mannose 21.7 g, fructose 15.08 g, glucose 24.5 g were present in saccharified CS whereas activities of β-glucosidase, endo-glucanase, and exo-glucanase were 46.8 ± 1.43, 53.5 ± 1.24 and 41.3 ± 1.31 U/mL, respectively. SEM analysis confirmed that every step, i.e., pre-treatment, saccharification, fermentation decreased crystallinity, and degree of polymerization of CS. After 6 h fermentation using 3:2 mL (S. cerevisae: C. cantarelli) inoculum size ratio at pH 6 and 35 °C, up to 92.5 g/L ethanol yield was obtained. The present study suggested that bioethanol production could be effectively enhanced by co-cultures of yeast using BBD from corn stover.