Ethanol production by Kluyveromyces marxianus HM36338: Optimization of fermentation conditions using response surface methodology

Bioethanol interests researchers as the greener alternative to fossil fuels. Fungal strains play a major role in this process. On the other hand, whey disposal in dairy industry is an issue of environmental concern. The cheese whey is a source of ethanol production. Kluyveromyces marxianus HM363381 is one such fungal strain used in ethanol production from crude whey. Here, we studied the process of ethanol production by the above strain and attempted to optimize the fermentation conditions adopting response surface methodology (RSM). A total of 20 fermentation trials were carried out which were produced from RSM with the central composite design using the three parameters, lactose concentration (5-20%), yeast extract (10-60%) and the inoculum size (5-14%). The experimental results were analyzed using analysis of variance (ANOVA) and lack of fit tests. The best operating conditions were found to be 14.14% (w/v) lactose concentration, 9.44 % inoculum size and 59.67 g/L yeast extract by keeping the other variables at their zero level, under which the strain Kluyveromyces marxianus HM363381 produced 59 g/L of ethanol. The results demonstrated a correlation of the experimental data to the dynamic models with high significant values of R-2 and, thus, could be useful for scaling up the ethanol production by fermentation of crude whey.