Screening Efficient Degradation Of Cellulose Strains And Preliminary Study On Utilizing Straw To Ferment Ethanol

The exploiture and utilization of cellulose resource attracts attention all over the world,and the key of development for that is seeking for efficient celluloytic strains.At the point of the deterioration of energy sources crisis and the waste of straw international tension,it has great realistic meaning for solving environmental pollution and energy crisis that screening and efficient celluloytic strains and using itto decompose straw and transform it into else forms of energy sources.In this study,20 strains were isolated via enrichment cultured,separated and purifyed from retton straw and bamboo,remains of termite,paunch of cattle,feces in byre,matter of midden,field soil etc.It was found that they can form the hydrolyze-zone clearly and degrade the filter paper into paste in 5 days through the experiment of cellulose-Congo red mediumand filter paper degraded.On the basis of these strains,4 strains of which can grow in the medium using straw as only carbon source and have the highest ability of degradation of straw less than 10 days had been obtained.They were 2 bacteria and 2 fungi,2 bacteria of strains(BC-1 & BC-4) were identified priliminarily as Pesudomonas ruhlandil and Pseudomonas flava,and 2 fungi(FD-7 & FD-8) were identified priliminarily as Penicillium claviforme Bainier and Penicillium leteum Zuckel respectively.In order to gain the biggest activity of CMC enzyme of the 2 fungi,liquid-state fermentation and solid-state fermentation had been investigated and ascertained primary. It was demonstrated that:(1)liquid-state fermentation:the fermentation time of FD-7 & FD-8 are 96h and 120h respectively,rotating speed is 130r/min,the fermentation temperature of FD-7 & FD-8 are 28℃and 37℃respectively.(2)solid-state fermentation:straw power/bean dregs is 8/2,initial ratio of C/N in medium is 10/1,initial pH of medium is 5.0,initial ratio of water in medium is 3/1,medium contents is 20 g,the percentage of inocilum is 10%.FD-7 & FD-8 were cultured under the conditions above, the activity of CMC enzyme were up to 119.28 IU/g and 117.67 IU/g respectively.FD-7 strain was cultured in solid fermentation medium,and then the fermentation product was saccharificated at high temperature,the conditions of which was confirmed as follows:the start time of saccharification is at 120 h,the optimum water temperature of saccharification is 50℃,the optimum time of saccharification is 48 h.The ethanol was obtained from the product of saccharification by Yeast.Followed by expanding scale of container,the percent conversion on straw to ethanol of final third scale is 10.36%and ethanol concentration in the fermented liquid is 20.72 mg/mL.