Detoxification vs. adaptation to inhibitory substances in the production of bioethanol from sugarcane bagasse hydrolysate: A case study

Abstract This study was undertaken not only to evaluate detoxification impact vs. adaptation on ethanologenic fermentation but also to optimize the fermentation condition to produce ethanol from Sugarcane Bagasse Hydrolysate (SBH). Detoxification by over-liming significantly improved the fermentability of the Concentrated Sugarcane Bagasse Hydrolysate (CSBH) by a wild strain of Barnettozyma californica. Compared to non-detoxified CSBH, ethanol production by the wild type strain increased from 1.233 g L−1 to 3.8031 g L−1, after 32 h and 24 h fermentation, respectively. Detoxification of SBH and CSBH showed a reverse effect on the adapted yeast. In detoxified CSBH, fermentation time increased to 32 h (3.084 g L−1) by adapted strain, while ethanol production was 3.803 g L−1 after 24 h by the non-adapted strain. Also, it should be noted that the parental yeast's capacity was found to be practicable in SBH without a detoxification and adaptation process. The screening and optimization of process parameters and critical medium components were done using the Plackett–Burman and Box–Behnken experimental design, respectively. (NH4)2SO4, (NH4)2PO4, ZnCl2, hydrolysate concentration, incubation temperature, and flask volume were found to be the main factors affecting ethanol production. Finally, a yield of 0.44 g g−1 was obtained, which is almost twice as high as the non-optimized medium. Taken together, these results indicate that hydrolysate detoxification and yeast adaptation through adaptive evolution and medium optimization are effective methods to overcome the bottleneck of lignocellulosic ethanol production.