Improving cellulases production with Neurospora crassa by morphology mutants screening

Abstract:

Filamentous fungi are widely used for large-scale production of cellulases. Morphological characteristics of mycelia under submerged condition are closely correlated with cellulases productivity. In order to find out the critical genes involved in the mycelial morphology development and cellulases production in liquid fermentation, 95 Neurospora crassa morphological mutants (named as SZY1-95) were screened for cellulases production. Compared with the wild type, cellulases production in four mutants SZY32, SZY35, SZY39 and SZY43 were significantly decreased, whereas mutants SZY63, SZY69, SZY87 and SZY11 produced much more cellulases than that of the wild type strain. Meanwhile, endo-beta-1,4-glucanase activity, beta-glucosidase activity, viscosity of broth and dry weight of these mutants were measured. The mycelial morphology of the mutants was also studied by microscope. Particularly, pellets were formed in mutant SZY11 and SZY43, whose viscosities were 25% and 50% of the wild type strain, respectively. Mutant SZY87 appeared long hyphae, and the viscosity of its broth was at least 2 folds of the wild type strain. These results indicate that a single gene deletion could influence the mycelial morphology in liquid fermentation, and increased the cellulases production. The low-viscosity related genes identified in our study will be the potential candidates for genetic modification of filamentous fungi.