5-39: Study of the effect of different consistencies on cellulases' optimum pH during enzymatic hydrolysis of steam exploded corn stover

The understanding of enzymatic saccharification of pretreated lignocellulosic material is of great importance. The conditions of pH and temperature performance of any particular enzyme are very well defined and it is clearly indicated by its manufacturer. It is known that commercial cellulases work best at pH around 4.8-5.0 and as a consequence this is widely used in the industry and the literature. In this study it was found that, contrary of the current understanding, optimum pH of cellulases is unexpectedly different than that recommend by its manufacturer at higher solids loads saccharification. The optimum pH changes depending on the consistency or solids loads of the matrix where the enzyme is acting upon in a way that is not previously disclosed. As a representative biomass, steam exploded corn stover was tested with cellulases at different pH, consistencies and ionic strength with the expectation of confirming the current optimal pH of around 4.8-5.0. Results showed that the optimum pH at lower consistency (1% w/w) is the same as the one that is recommended by manufacturer; however at higher consistency the value obtained was higher (pH 5.5 and pH 6.5) instead of the pH 4.8. The difference could represent of up to 30-50% higher yields and hence of great importance for the economics of any second generation fuel production.