Induction, screening and identification of Coniothyrium minitans mutants with enhanced β-glucanase activity

The production of β-glucanase in a mycoparasitic fungus, Coniothyrium minitans, was investigated using a wild type strain 2134. Through ultraviolet (UV) irradiation of strain 2134, four mutants, M11-3B2, A7-3D, A8-1 and A10-4, exhibiting enhanced β-glucanase activities were isolated. Strains A8-1 and A10-4 were constitutive mutants that expressed barley β-glucan hydrolysing activity in the absence of a supplemental inducer (β-glucan substrate). Supernatant from A8-1 and A10-4 cultures grown in potato dextrose broth (PDB), the medium without β-glucan, had maximum levels of β-glucanase activity on average 10 times greater than the wild type strain 2134. M11-3B2 had low levels of constitutive β-glucanase expression and enhanced laminarin hydrolysing activity when grown in presence of β-glucan-rich substrate.