Optimization of aeration rate and timing for ethanol production from date by-products by Saccharomyces cerevisiae using response surface methodology

Abstract

Aeration is one of the significant factors affecting yeast physiology and impacts ethanol production. The aim of this study was to optimize the aeration rate and aeration time of ethanol production by Saccharomyces cerevisiae using a centered composite model based on response surface methodology (RSM). The aeration rate (0.2, 0.5, 1.5, 2.5 and 2.9 vvm), the aeration timing (1.2, 2, 4, 6 and 6.8 h) with a constant agitation rate (120 rpm) were applied. The ethanol production medium was date juice containing 150 g/L of total sugar and 1 g/L of urea. The fermentation was carried out at 30°C in a 2-L fermenter. Response surface methodology analysis showed that the optimal aeration for ethanol production was an aeration rate and aeration time of 1.5 vvm and 1.2 h, respectively. Under the optimal conditions, the ethanol concentration (P), productivity (Qp) and ethanol yield (Yp/s) were 82.74 g/L, 3.14 g/L/h and 0.71 g/g, respectively. Under an unaerated condition (control treatment), the P, Qp and Yp/s values were 68.30 g/L, 2.59 g/L/h and 0.61 respectively. The results clearly indicated that optimal aeration can improve ethanol production.