5-11: Continuous enzyme production and enzymatic hydrolysis of alkali-pretreated sugar cane bagasse by Cellulomonas flavigena PR-22

Enzymatic hydrolysis of hemicellulose and cellulose from alkali-pretreated lignocellulose is a promising method for saccharification that does not generate inhibitory compounds, thus the expensive step of detoxification and some material disposal is avoided. The objective of this work was to improve soluble sugar accumulation, from NaOH-pretreated sugar cane bagasse, using a coupled system for enzyme production and saccharification. The continuous enzyme production was carried out in a Bubble Column Reactor (BCR), at a dilution rate of 0.1 h^-1, with the hyper-producing mutant PR-22 from Cellulomonas flavigena. The enzymatic effluent from the BCB, composed by CMCases (127 IU l^-1 h^-1) and xylanases (2440 IU l^-1 h^-1) with 0.5 g l^-1 protein was feed to a Stirred Tank Reactor (STR) for the saccharification process of 3 % (w/v) alkali-pretreated sugar cane bagasse. The operation conditions in the STR were pH 7, 150 rpm and 50 °C, reaching 16 ± 1.13 g l^-1 of soluble sugars in the steady state; this means a saccharification yield of ca 70% of the theoretical. This strategy can be applied to a bio-consolidated process and therefore further work will be focused in a system for continuous enzyme production and simultaneous saccharification and fermentation of sugars to ethanol.