Detoxification of sugarcane Bagasse Dilute-Acid Hydrolyzate by Overliming for bioethanol production

During the process of acid pretreatment of sugarcane bagasse, unwanted products such as furans and phenolic compounds are produced which show Inhibitory effect on the growth of microorganisms. In this study, the effect of over-liming detoxification was evaluated by full factorial statistical method where three factors of pH, temperature and reaction time were selected as independent variables. Ethanol production efficiency by Saccharomyces cerevisiae was compared in non-detoxified and detoxified treatments. The Overliming involved increasing the pH of hydrolyzes to 10, 11 and 12, keeping for 30 and 60 min at temperatures of 40 and 60 °c, followed by readjustment of the pH to 5.5. The mutant strain of Saccharomyces cerevisiae PTCC 5052 was cultured in the detoxified and non-detoxified media, containing bagasse hydrolysate. Based on the results increasing the pH, time and temperature resulted in more effective destruction of furfural and lead to better fermentability for hydrolyzes. furfural was decreased 73% after Overliming for 60 minutes, at 60 C, pH 12 and ethanol yield was increased 81% in comparison with non-detoxified hydrolyzed in 18h batch cultivation. But one disadvantage of this method is reducing simultaneous sugars and inhibitor during the reaction, so that, in pH 12 and 60 for 60 minutes, respectively, 47% and 73% of total sugars and glucose was decreased.