08.08.2015   Advances in Biochemical Engineering/Biotechnology

В — Glucosidase

An “efficient” cellulase system requires sufficient в-glucosidase (BG) to hy­drolyze cellobiose produced by the action of the CBHs to prevent their prod­uct inhibition [38]. The addition of BG to a complex cellulase mix such as the Novozymes Celluclast 1.5 L dramatically improves the extent and, during the later stages of hydrolysis, the rate of cellulose saccharification. This is re-

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Fig. 6 Improvement of PCS-hydrolyzing cellulases by increasing levels of p-glucosidase (BG) activity. Comparison of T. reesei cellulase preparations, with (B) and without (A) supplementation with purified A. oryzae BG, in the hydrolysis of cellulose present in acid pretreated corn stover demonstrates a significant benefit in reducing the amount of en­zyme required. Addition of small amounts of BG, present as a few percent of total protein, allowed hydrolysis of 80% of the cellulose to glucose with an enzyme protein dosage 1.8-fold lower that the unsupplemented cellulase

flected in Fig. 6, where the T. reesei strain used to produce Celluclast 1.5 L was compared to the same strain expressing Aspergillus oryzae BG in hydro­lysis assays. Due to relief of the product inhibition at high solids loadings (13.5% w/w in this example), the amount of total enzyme protein required to hydrolyze 80% of the cellulose to glucose was reduced by nearly twofold. At this solids loading, the beneficial effect of BG addition was saturated when it reached ~ 5% of the total enzyme protein, but higher solids would require higher BG levels or a more active BG.

4.2.2