Improved simultaneous saccharification and fermentation of bioethanol from industrial potato waste with co-cultures of Aspergillus niger and Saccharomyces cerevisiae by medium optimization

For economical production of bioethanol from industrial wastes, enzyme cost for saccharification is the significant cost for the overall process. Therefore, the fermentation medium optimization for simultaneous saccharification and fermentation (SSF) by using co-culture of Aspergillus niger and Saccharomyces cerevisiae for potato wastes was undertaken in this study. A medium consisted of waste potato mash, malt extract and FeSO₄·7H₂O were defined as the optimum medium for co-culture of A. niger and S. cerevisiae SSF. Statistical optimization of defined medium was conducted using central composite design. Optimization results suggested that optimum concentrations of industrial waste potato mash, malt extract, and FeSO₄·7H₂O were 92.37 g/L, 59.42 g/L and 0.159 g/L, respectively. Under the optimal medium, 35.19 g/L ethanol production and 31.36 U/ml glucoamylase activity giving a yield of 0.38 g ethanol/g starch and 0.34 U/g starch respectively, achieved at 30 °C and 120 h of fermentation.