Study On Degradation Of Fibrous Agricultural By-products By Neurospora.crassa And Ethanol Production From Its Product

In this paper, high vitality cellulose was produced by Neurospora crassa on low-cost agro-industrial residues in rich of fibers in solid-state fermentation. Neurospora crassa, which could produce high amount of cellulase, was isolated and mutated from the traditional fermented food in Jiangxi province. The composition of culture medium were optimized to enhance the vitality of cellulose. Effect of culture conditions on reducing sugar from fibrous materials were investigated. And the compositions of fermentable sugar, which came from the degradation product under this optimal culture medium, were analyzed by gas chromatography. This work aim to select the best yeast strain and fermentation mode for cellulosic ethanol production, and provid theoretical foundation and scientific basis for efficient production of cellulosic ethanol. The main results are as follows:1. We took advantage of bean hull, bean dreg, rice straw, beer lee and distillers’ grains as raw material for solid state fermentation. Firstly, the cellulase activity were compared among them when only one material as sole carbon source. And then choose the better of then, mixed and inoculated Neurospora crassa for solid state fermentation. The result show that the highest cellulose enzyme activity appeared in the bean hull、distillers’ grains and bean dreg mixed medium. The effects of medium composition were evaluated by using a Plackett-Burman design. The results showed that bean hull, distillers’ grains and(NH4)2SO4 were the main factors while the other additive had no significant effects on the cellulase production. Then, the central composite design and response surface analysis were used to determine the optimal levels of the main factors. The optimized conditions were:64% bean hull, 34% distillers’ grains and 2% ammonia sulfate. Under these conditions, the activity of cellulases significantly improved 141.88%, from 1.17IU/g to 2.83IU/g.2. The single-factor experiment had been used to investigated the effect of culture conditions on reducing sugar from fibrous materials. The result show that initial p H value, initial water content value, incubation temperature and inoculum dose were the main factors while the other factors had no significant effects. Then the orthogonal experiment were used to determine the optimal levels of the main factors. The ethanol fermentation ability about three strains of yeast on fiber degradation was compared. Issatchenkia Orientalis was chosen for doing the further research as it has the strongest ethanol conversion. Contrast the yield of ethanol production in SHF、SSF and NSSF and found that NSSF was the best mode for ellulosic ethanol production.3. We took advantage of modified NSSF to produce cellulosic ethanol, and five four factors on the influence of fermentation production were studied. The optimum process parameters of cellulosic ethanol fermentation were : solid-to-solution ratio 1:10, the addition content of nitrogen source 1%, yeast inoculum dose 5%, culture temperature 34℃, fermentation time 36 h. Under this condition, the final yield of ethanol was 22.55g/100 g. The filer composition of residue were detected, and the result shows that lignin and hemicellulose were the main component in residue, and the content of cellulose was reduced greatly. The utilization of cellulose reached 57.54%.