| The screening of cellulose-degrading strains and the fermentation conditions and the characteristics of cellulase and the effects of fermentation on medium composition were studied optimized in this paper as well as the ready-to-use starters. The main results are as follows:By using cellulose congo-red culture medium and determination of celulase to repeat screening from the litter-rich soil, we got two highly active cellulolytic strains 3-7 and W13. According to the traditional morphological characterisctics, physiological and biochemical properties, the strain 3-7 was identified as Trichoderma viride and the strain W13 was identified as Staphylococcus pasteuri, respectively.The optimal liquid-state fermentation conditions for cellulase were determined and the results are as follows. The sutiable fermentation conditions of the strain 3-7 were CMC-Na 1.5%, yeast extract 1.5%, NaCl 0.4%, MgSO4·7H2O 0.05%, KH2PO4 0.4%, CaCl2 0.03% and the initial pH was 5 and culturing 4d at 30℃. The sutiable fermentation conditions of the strain W13 were CMC-Na 1.5%, yeast extract 1.5%, NaCl 0.2%, MgSO4·7H2O 0.05%, KH2PO4 0.4%, CaCl2 0.03% and the initial pH was 6 and culturing 4d at 37℃.The effects of carbon and nitrogen sources, carbon source to mineral solution ratio, fermentation temperature on cellulase production under the solid state culture were studied. Results for the 3-7 showed that: the ratio of the Distiller's grains and wheat bran was 7:3, soya bean meal 1%, carbon source to mineral solution ratio was 1:1, inoculum size was 0.5ml, culturing 3d at 30℃. Under these conditions, the highest yield of FPA and CMCase reached 1463.97U/g and 7105.92 U/g, respectively. For the strain W13 the sutiable fermentation conditions were: the ratio of the Distiller's grains and wheat bran was 7:3, soya bean meal 2%, carbon source to mineral solution ratio was 1:3, inoculum size was 1.5ml, the initial pH was 7, the culture temperature was 30℃, culturing 4d. Under these conditions, the highest yield of FPA and CMCase reached 270.64U/g and 397.29U/g, respectively.The analysis of fermented product indicated that 34.62% of coarse cellulose was decomposed. The content of fat and ash had almost no change after fermentation. The studies on enzyme system showed that xylanase, amylase, mannaseβ-glucanase and acid protease were inclouded in the fermented products. Magnification of cellulase was studied through the study of the fermenter. FPA and CMCase reached 470.75U/g and 1301.57U/g, respectively.For the strain 3-7, the optimal reaction temperature of CMCase and FPA activity were 50℃and 60℃, respectively. The optimal reaction pH value was 4.6 and 4.8, respectively. The FPA and CMCase kept more than 93% after thermal treatment for two hours when the temperature bellowed 50℃and kept more than 90% from pH 4.6 to 5.4 when put them at 4℃for 24h. Cu~2+ and Ca~2+ could stimulate the enzyme activities. Fe2+ and Mn2+ inhibited the enzyme activities. Zn~2+,Mg~2+,K~+,Na~+ showed no significant effect on the enzyme activities. For the strain W13, the optimal reaction temperature of CMCase and FPA activity were 60℃and 55℃, respectively. The optimal reaction pH value was 5.8. The FPA and CMCase kept more than 90% after thermal treatment for two hours from 35℃to 55℃and kept more than 90% from 5.2 to 6.0 when put them at 4℃for 24h. Cu~2+ and Mg~2+ could stimulate the enzyme activities. Ca~2+,Fe~2+,Mn~2+,Zn~2+,K~+,Na~+ inhibited the enzyme activities.The drying methods and the preparation condition and the fermentative properties of ready-to-use starters were studied. The results showed that the fermentative properties were best when the preservative was 20% sucrose under the vacuum drying. Under these conditions, the highest yield of FPA and CMCase reached 1198.80 U/g and 5861.98 U/g, respectively. |
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