Cellulase Producing Bacteria Breeding, Solid-state Fermentation Conditions And The Nature Of Research

The eighty-three cellulolytic strains were isolated from decayed wheat straw, maize straw,rice straw and rotten cow dung. The two mutant strains were obtained from parent strains F2 and A8. The study on the solid fermentation conditions and properties of mutant strains was carried out. The results showed:1.The four wild fungi named F1,F2,T9 and A8 were obtained with higher cellulase activities from them and had no harm to animals used as a subject of experiment.2.The dynamic analysis of cellulase activities with solid fermentation by four strains showed that the cellulase activities of A8 and F2 are higher than those of others and possessed the highest cellulase activities when culture time was 72～96hours. The strains had the highest cellulase activities used rice straw as fermentation substrate.3.The parent strains A8 and F2 were illuminated under 30W unltraviolet lamp. The mutant strains UA8-Ⅰ2-2 and UF2-Ⅱ6-2Ⅱ were obtained by isolation of double layer avicel plate, purification of PDA plate and first, second screening. The cellulase activities of mutant strains UA8-Ⅰ2-2 and UF2-Ⅱ6-2 were 10.63,36.1,62.25IU/g and 8.6,46.02,19.56IU/g respectively.4.The different composition of medium had some certainly effects on cellulase activities. The highest cellulase activities were obtained when the ratios of rice straw and wheat bran of A8 and F2 were 7/3 and 6/4. The strains grew quickly on a medium containing vegetable oil residual as nitrogen source. and secondary cellulase activities to inorganic nitrogen source. The 1g/L tween-80, NaAc and Vc promoted cellulase production. Ca2+,Fe2+,Mg2+,Mn2+ had no apparent effects on cellulase activities.5.The orthogonal experiment of solid fermentation technologies of A8,F2 UA8-Ⅰ2-2 and UF2-Ⅱ6-2 were carried out with solid basic medium under the conditions of the same inoculation method,inoculation concentration and the same culture temperature. The results showed that the water/substrate ratio,fermentation time had larger effects on cellulase activities. The optimum fermentation technologies of A8/T9/UA8-Ⅰ2-2/ UF2-Ⅱ6-2 were water/substrate ratio 3 fermentation time 4 days,vegetable oil residual 3%,KH2PO4 1.5%; water/substrate ratio 3, fermentation time 4 days, vegetable oil residual 5%,KH2PO4 1%; water/substrate ratio 3.5, fermentation time 5 days,vegetable oil residual 3%,KH2PO4 1.5%; water/substrate ratio 3.5,fermentation time 5 days,vegetable oil residual 1%,KH2PO4 1% respectively.6.The optimum pH and temperature for components of cellulase of mutant strain UA8-Ⅰ2-2 and UF2-Ⅱ6-2 were pH 4.8 and 60℃. The cellulase of mutant strain UA8-Ⅰ2-2 had good pH stability when pH range was 3.5～7.0. The survival cellulase activities were above 77 percent of those of untreated cellulase in pH 3.0. The strain UF2-Ⅱ6-2 was similar to that one. The cellulase of two mutant strains had good heat stability in the range of 35～60℃. The cellulase of two mutant strains had strong resistance to pepsin.7.There are amylase, proteinase and so on in the product of fermentation.8.The raw cellulase powder of the mutant strain UA8-Ⅰ2-2 mixed with that of UF2-Ⅱ6-2 with the ratio of 8/2,which improved the coordination among different components of cellulase.9.The hydrolysis experiment of raw cellulase powder showed that concentration of reducing sugar was 960mg/g when the concentration of raw cellulase powder was 2% and hydrolysis time was 24 hours. The rate of saccharification was 3.71% when the concentration of raw cellulase powder was 3% and hydrolysis time was 24 hours.