Screening Of Cellulase-overproduction Mutant And Study On The Saccharification And Lactic Acid Fermentation Of Corn Stalk

The cellulase production strain T.viride 9211 was treated with UV and EMS. The mutant T.viride 8140 was obtained and the cellulase towards CMCase, FPA reached 18.81IU/ml, 2.08IU/ml respectively. The effects of compositions of culture medium on cellulase production were investigated and the optimal culture media is: (g/L) Avicel 10, wheat bran 10, peptone 0.4, urea 0.4, (NH4)2SO4 2.0, CaCl2 0.2, MgSO4 0.3, KH2PO4 2.0; (mg/L) FeSO4.7H2O 5.0, MnSO4.H2O 1.6, ZnSO4.7H2O, 1.4, CoCl2 2.0; (ml/L) tween-80 2.0. The effects of fermentation conditions including incubating temperature, medium pH, rotation rate and amount of inoculation were also investigated and the optimal conditions is: 28℃, 5.5, 210rpm and 4~6% respectively, 300ml Erlenmeyer flask containing 50 ml medium. Under this condition, the CMCase and FPA reached 25.0 IU/ml, 2.65 IU/ml respectively.Corn stalk was pretreated by means of high temperature and pressure, dilute acid, dilute alkali lye and liquid ammonia. The results show that the saccharification of cellulose could be enhanced by the pretreatment, of which the dilute alkali pretreatment is the best. The optimal condition of pretreatment is: concentration of NaOH 1.0%, 15℃, ratio of solid-liquid 1:20. Under this condition, the corn stalk was pretreated for three days, and the saccharification rate reached 73.5%, the loss rate of hemicellulose was 33.1%.A strain of lactic acid bacteria LF24 was isolated from high-temperature fermented cabbage and it was identified as Lactobacillus plantarum. Its fermentation capacity was studied, and the results demonstrated that it has a high rate of acid production, the conversation rate of lactic acid from glucose reaches above 90%. The strain LF24 is thermophilus and it can be well fermented at 50℃, which is benefit to the process of simultaneous saccharification and fermentation.