| Trichoderma viride,a filamentous fungus with complete cellulase system,can secrete loads of highly active cellulase and effectively degrade lignocellulose for biomass recycling.In this study,two strains of T.viride were isolated respectively from rhizosphere soil of Glycyrrhiza uralensis(T.viride XJ)and Saposhnikovia divaricate(T.viride AG)in different habitats.Cellulase production of the strains growing on two lignocellulosic substrates,i.e.corn stalk and liquorice residue was assessed.Pot experiment was conducted to evaluate the effects of soil sterilization and the fermentation residue on the growth of Zea mays.The biological characteristics of the two strains,differences of the two substrates,optimization of fermentation conditions and growth effects of liquorice residue on Z.mays were studied to provide a basis for making full use of T.viride and promoting the recycling of lignocellulosic wastes.The main test results are as follows:1.The mycelia growth and spore formation of the two T.viride strains on potato dextrose agar medium were observed.There was no significant difference between the two strains in response to different environmental conditions.The optimal temperature for cultivation of both strains was 28?,and the optimum pH was 6.With concentration of PEG6000 lower than 24%,the mycelial growth and spore formation of the two strains were less inhibited.There was a linear correlation between mycelia growth and incubation time of both strains.2.Using corn stalk as substrate,the optimal fermentation temperature of both strains was 28?.The optimum initial pH for cultivation of T.viride XJ was 6,and that of T.viride AG was 7.The optimum initial solid to liquid ratio was 1:4 for T.viride XJ,and 1:5.5 for T.viride AG.The filter paper cellulase(FPase)activity of T.viride AG was significantly higher than that of T.viride XJ in the substrate with initial solid to liquid ratio of 1:5.5.Among all tested treatments,the reducing sugar was consumed by the two T.viride strains.3.Using liquorice residue as substrate,the optimum initial pH for cultivation of both strains was 6.The optimum initial solid to liquid ratio was 1:2.5 for T.viride XJ,and 1:3 for T.viride AG.The FPase activity of T.viride AG was significantly higher than that of T.viride XJ in the substrate with initial solid to liquid ratio over 1:3.The optimal fermentation temperature of T.viride AG was 28?,and that of T.viride XJ was 23?-28?.The FPase activity of T.viride XJ was significantly higher than that of T.viride AG at temperatures below 28?.Among all tested treatments,the reducing sugar was accumulated by the two T.viride strains.4.The FPase activity of T.viride AG was higher than that of T.viride XJ in one-factor experiment.The liquorice residue was better than corn stalk for inducing FPase production by T.viride.The optimal match for the production of FPase was T.viride AG and liquorice residue.The variation partitioning indicated that the response of T.viride XJ to different substrates was consistent with that of T.viride AG,and the differences of FPase activity between tested strains depended on the ecological adaptability of the strains.5.Box-Behnken design was used to establish the mathematical model to improve the FPase activity.The optimal fermentation conditions for the production of FPase from T.viride AG was obtained as follows: the initial solid to liquid ratio of 1:2.8,the incubation temperature of 28?,the initial pH of 6.2,and the fermentation time of 3.4 days.Under the optimized conditions,the FPase activity was 1.81 U/g,which was close to the theoretical value of 1.76U/g predicted by the developed model,and it was 1.85-fold higher than that produced before the optimization.6.The growth parameters of Z.mays were decreased by the interaction of different liquorice residues and soil treatments.Soil sterilization had no significant effect on plant height,stem diameter,total biomass and auxin concentration of Z.mays.Superoxide dismutase activity and chlorophyll content of Z.mays treated with fermented residue were significantly higher than those treated with unfermented residue.The activities of alkaline phosphatase and urease were significantly improved in all liquorice residue treatments. |
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