Optimizing condition of enzyme production of cellulose-decomposing fungus for straw and breeding mutant strains with high cellulase activity.

Three strains of cellulose-decomposing fungus,viz.,F-1,F-2 and F-3,were selected as experimental materials.By adjusting pH,inorganic salts components and carbon sources of medium,the condition of enzyme production of the three cellulose-decomposing funguses was optimized.Furthermore,their mutant strains were obtained by UV mutation.The results showed that,after being cultured in fermentation liquid medium with different initial pH for 6 days,the filter paper cellulase (FPase) of the three strains reached the highest,with 8.0,9.0,9.0 as the optimal initial pH value respectively.The carboxymethel cellulase(CMCase) reached the highest after 10 days,of which optimal initial pH were 8.0,7.0 and 7.0,respectively.The pH value of medium all decreased after some time,and among the three strains the F-2 declined the most obviously.The F-1 of which cellulase activity was relatively higher than the other two was cultured on the medium with different inorganic salts components and carbon sources.The rice husk powder was found to be the most suitable carbon source for enzyme production and the suitable inorganic salts were CaCl2 0.4,MgSO4·7H2O 2.5,NaCl 10.0,(NH4)2SO4 2.6,KH2PO4 2.7 g,H2O 1000 mL.After UV mutation on the three strains of cellulose-decomposing fungus,four mutant strains which came from F-1 and F-3 were obtained.Among the four mutant strains,the CMCase of F-1-U1 and F-3-U1 was 348.22 and 282.07 U/mL,being 1.85 and 2.25 times as compared with the original strains respectively.