Effects of Different Induction Media as Inducers on Laccase Activities of Pleurotus ostreatus Strains in Submerged Fermentation

Sequential submerged cultivation with different induction media as inducers of ligninolytic enzyme production by Pleurotus ostreatus strains was assessed by measuring laccase activities. An unconventional material, alkali lignin, was used for the first time as an inducer for different strains to enhance laccase activity. The P. ostreatus strains secreted similar but relatively high levels of laccase activity when the induction media contained alkali lignin with or without glucose. The laccase enzyme of different P. ostreatus strains in the different media exhibited large differences, and the wild strain YAASM 0568 exhibited enhanced production of laccase compared to other cultivated strains. The laccase activities of wild strain YAASM 0568 were nearly 3.4-, 3.3-, and 5.4-fold higher than that for cultivated strains CCMSSC 00322, CCMSSC 00406, and CCMSSC 00336, respectively, when the induction media contained alkali lignin, inorganic salt, and vitamin B-1. In general, induction media containing alkali lignin with or without glucose were favorable for laccase secretion. The results revealed that the type of induction material and the nature of the fungus play important roles in the expression of ligninolytic enzymes. These findings would be helpful for selection of the appropriate type of strain and for optimization of integrated industrial ligninolytic enzyme production.