Biomass, laccase and endoglucanase production by Lentinula edodes during solid state fermentation of reed grass, bean stalks and wheat straw residues

Mycelium growth rates, biomass concentration (estimated as glucosamine content) and laccase and endoglucanase secretion were monitored during solid state fermentation (SSF) of wheat straw (WS), reed grass (RG) and bean stalk (BS) residues by Lentinula edodes strains 119, 121, and 122. In a first experiment, these strains were subjected to screening regarding their growth rates and biomass yield, where strain 121 proved to be the fastest colonizer. However, the greater biomass yield at the end of colonization was demonstrated by strain 122 on BS (465.93 mg g(-1) d.w.). In a second experiment, growth characters, as well as endoglucanase and laccase production patterns of the selected strains 121 and 122 were monitored at three intervals i.e., at 33, 66, and 100% of substrate colonization. BS furnished the highest endoglucanase production for strain 121, while RG for strain 122. A strain and substrate-dependent behaviour of the enzyme secretion was detected, with strain 122 presenting maximal endoglucanase activity in all substrates at the initial (33%) and final (100%) stages of colonization (0.64-0.90 and 0.79-0.97 U g(-1,) respectively). However, in strain 121 the peak of endoglucanase production was detected in the early stages of colonization (at 33% on WS and at 66% on RG and BS). Laccase activity showed increased values (maxima on WS, 353.68 and 548.67 U g(-1) by strains 121 and 122, respectively) at 66% of colonization. Correlation analysis of growth data demonstrated negative relations between growth rate and biomass yield and between laccase and endoglucanase activities on WS and RG substrates fermented by strain 122. Finally, possible relations of growth parameters with nutritional constituents of the substrates were investigated.