Ethanol production in biofilm reactors from potato waste hydrolysate and optimization of growth parameters for Saccharomyces cerevisiae

Bioethanol production is of great interest to meet the renewable energy demand and reduce the negative environmental impacts of petroleum fuel while providing energy security for countries. In order to make ethanol production cost-competitive, inexpensive and easily available feedstocks are needed as well as novel processing technologies with higher productivities. In this study, biofilm reactors have been utilized as a novel approach for production of bioethanol from potato waste hydrolysate by optimizing the growth parameters for Saccharomyces cerevisiae in repeated-batch biofilm reactor. First of all, in order to achieve a successful biofilm formation, plastic composite supports (PCS) evaluated and the PCS composed of polypropylene, soybean hull, soybean flour, yeast extract, and salts was selected for ethanol fermentation with S. cerevisiae. Then Box-Behnken design of response surface method (RSM) was employed to optimize the growth parameters, pH, temperature, and agitation. Optimum conditions for ethanol fermentation was found to be pH 4.2, temperature 34 °C, and 100 rpm resulting 37.05 g/L ethanol with a 2.31 g/L/h productivity and 92.08% theoretical yield. The results indicated that biofilm reactors with PCS can enhance the ethanol fermentation from industrial potato wastes.