Screening of fungal mutant strain with high laccase yield by N+-implantation and enzyme production condition optimization

The basidiospores of Pleurotus ostreatus WY01 were exposed to N+ beam and the treated basidiospores were screened in RBBR-containing PDA plates. Then the laccase activities of the selected strains were determined by ABTS, and a mutant named ADW-08 with high yield of laccase was obtained. The maximum activity of laccase of ADW-08 increased up to 7.78 U/g, 2.8 times of the original stain, and its laccase production ability was stable in high carbon and low nitrogen rape straw solid medium (SM). Results showed that glucose as carbon source was obviously superior to sucrose, maltose, wheat bran and soluble amylum in solid culture for ADW-08. Ammonium tartrate as nitrogen source was more suitable than other nitrogen sources for the laccase secretion. The optimal initial pH was 5.0 or 6.0. The ability of laccase production clearly increased by ABTS and veratryl alcohol induction, but was inhibited by Tween 80. When the optimum parameters for laccase production got from orthogonal design were as follows: glucose 15 g/L, ammonium tartrate 0.2 g/L, pH 5.2, the peak value of Lac activity was 8.33 U/g. (authors)