The Study On Cellulase Production By Different Inducing Carbon Sources And The Relationship Between The Inducing Carbon Sources And Enzymatic Hydrolysis Efficiencies Of Substrates

Lignocellulose is a kind of renewable biomass and the cellulose in it could be hydrolyzed into glucose by cellulases,which in turn could be converted into fuel ethanol or other high value-added products.Cellulase plays an important role in the hydrolysis process of lignocellulose,but the commercialized cellulase is still expensive.Therefore,it becomes one of the major research foci to improve the efficiency of enzymatic hydrolysis and reduce the production cost of cellulase.In order to investigate the effects of different inducing carbon sources on producing cellulases and the enzymatic efficiencies of the produced cellulases on different substrates,in this study,Trichoderma reesei and Aspergillus niger were used as enzyme-producing strains,and cellulose powder,sodium carboxymethyl cellulose,untreated bagasse,bagasse treated with 2%Na OH,bran and straw were used as inducing carbon sources to induce cellulase production.The results showed that the best inducing carbon sources for Trichoderma reesei and Aspergillus niger were straws,and the maximum filter paper activity of the cellulase induced by straws were0.248 IU/ml and 0.152 IU/m L,respectively.To further improve the enzyme activity of cellulases,cellulases from the two producer strains which were induced by different carbon sources were first concentrated and then mixed with different volume ratios.The results showed that,when the cellulases from Trichoderma reesei and Aspergillus niger,which both were induced by straw,were mixed at the ratio of 9:1,the total filter paper activity of the mixture reached the maximum of 0.619 IU/m L,which was 28.4%higher than that of the enzyme from Trichoderma reesei alone（0.482 IU/m L）.To investigate the enzymatically hydrolysis efficiency of the cellulase mixtures,in this study,different cellulase mixtures were set up by mixing the cellulases from T.reesei and A.niger induced with different carbon sources and the five above mentioned carbon sources were enzymatically hydrolyzed with the cellulase mixtures.The results suggested that except for cellulose powder,the enzymatic hydrolysis efficiencies of the other four substrates were higher than those using commercial enzyme CTec2 at the same amount of enzyme loading.Among them,when the bagasse treated with 2%Na OH was hydrolyzed with the cellulase mixture that made up with crude enzymes from T.reesei and A.niger both induced with straw at the ratio of9:1,the enzymatic hydrolysis efficiency was as high as 94.52%.The basic characteristics of the cellulase mixture were explored in this study and the results showed that the optimal reaction temperature was between 50-60°C,the optimal p H was about 5.0,the enzyme activity was promoted by 0.01 mol/L Ca²⁺but inhibited by 0.01 mol/L Mg²⁺,Zn²⁺,Mn²⁺and Cu²⁺.The results of this study shows that the enzymatic efficiencies of cellulases induced using different carbon sources on the same substrate were different,which suggested that it is necessary to optimize the combination of cellulases for a particular lignocellulose material to achieve the maximal enzymatic efficiency.