Optimization of ethanol production from microwave alkali pretreated rice straw using statistical experimental designs by Saccharomyces cerevisiae

Ethanol production from agro-waste provides an alternative energy-production system. Statistical experimental designs were used for optimization of critical nutrients and process variables for ethanol production. The critical nutrients and process variables were initially selected according to a Placket–Burman (PB) design. Selected factors (inoculum level 1–5%, pH 4.5–7, temperature 25–35 °C and urea concentration 0.25–0.75 g/L) were optimized by response surface methodology (RSM) based on a three-level four-factor Box–Behnken design (BBD). Under optimum conditions of inoculum level 3%, pH 5.75, temperature 30 °C and urea concentration 0.50 g/L maximum ethanol production obtained 13.2 g/L from microwave alkali pretreated rice straw with ethanol productivity 0.33 g/L/h. Under optimum conditions ethanol production studied at fermenter level and obtained ethanol concentration 19.2 g/L, ethanol productivity 0.53 g/L/h and ethanol yield to consumed sugar 0.50 g/g. These results indicated that ethanol production can be enhanced by optimization of nutritional and process variables.

► Utilization of agro-waste which creates environmental management problems. ► Crude unprocessed enzymes used for hydrolysis of alkali pretreated rice straw. ► Factors affecting ethanol production screen out by PBD. ► Most significant factors studied by BBD affecting ethanol production by Saccharomyces cerevisiae.