Sexual Crossing of Myceliophthora heterothallica Strains Produce Progeny with Improved Enzymatic Degradation

The fungi from the genus Myceliophthora have a large set of enzymes targeting linkages in plant polysaccharides. Most of these have not been characterized, and their role in degradation is unknown. Utrecht University researchers, led by Maria Victoria Aguilar-Pontes, now used sexual crossing and screening in Myceliophthora heterothallica to identify specific enzymes associated with improved sugar beet pulp saccharification.

Two genetically diverse M. heterothallica strains, CBS 203.75 and CBS 663.74, were used to generate progenies. One progeny, named SBP.F1.2.11, had improved saccharification activity after growth on sugar beet pulp. Analysis of the progeny and parents showed that only 17 of 133 secreted enzymes were more abundant in progeny SBP.F1.2.11. One particular enzyme, named Axe1, was more abundant in the progeny. Supplementing Axe1 to the parent CBS 203.75 enzyme set improved release of xylose and glucose from sugar beet pulp.

Saccharification of sugar beet pulp was improved by supplementing enzyme mixtures with Axe1. Sexual crossing and selection of M. heterothallica was proven plausible as a strategy to improve enzyme mixtures for plant biomass degradation.