Tuesday, May 3, 2011
Cellulose hydrolysis requires the synergistic activities of three types of enzymes: exo-glucanases, endo-glucanases and beta-glucosidases. Exo-glucanase HjCel6A (CBH2) comprises more than 30% of the total protein in Hyprocrea jecorina whole cellulase. Improvement of the specific activity of HjCel6A will result directly in a significant reduction of enzyme dose required to hydrolyze biomass substrates. In particular, HjCel6A has been identified as a limiting activity. Recently we expressed ~3000 single mutation variants of HjCel6A in H. jecorina and screened them for improved thermostability, and specific activity on phosphoric acid swollen cellulose and biomass substrates. Combinatorial libraries were designed and built based upon the results from the single mutation variants, and evaluated for performance enhancements. Here we present the results of screening of HjCel6A combinatorial libraries which has led to the identification of variants that display improved performance on biomass substrates.