Study On The Screening And Identifying Of Cellulolytic Mixed Strains And The Condition Of Saccharification

This question for discussion was advanced background by turning worse of energy sources crisis and the waste of straw cellulose with the aim of searching for a kind of mixed strains which can decompose straw cellulose efficiently. So the thesis was began with isolating strains from soil covered with straw and vegetation, and then via enrichment culturing, separating and purifying, 14 strains were gotten which can grow in the solid medium with CMC-Na as an only carbon source. On the basis of these strains, 10 strains of fungi which had better adaptability and can decompose cellulose efficiently is screened through the experiments of decomposition of filter paper and identifying of cellulose-Congo red medium. By solid fermentation experimentations, the growth period and the output of cellulose of the 10 strains could be known quantificationally and 4 kinds of mixed strains were chosen. By comparing the carboxyl methyl cellulose (CMC) activity, the filter paper activity (FPA) and the mutual adjustability of every combination, the best one was finally chosen and identified as Mucor sp.and Aspergillus sp..In order to gain the biggest activity of the mixed strains, solid-state fermentation including the preparation of germs, culture medium and culture condition were optimized using single factor and orthogonal experiments. The results showed that when mycelium cultured three days were inoculated by 20% at 1:1 in the solid medium that is straw: bran=8:1, (NH₄)₂SO₄=2.5%, solid: liquid=l:1.5, and then cultivated at natural pH, around 28℃for 5d, 732.41U as the highest CMC activity can be achieved, but when the gross and radio of inoculation were turned into 30% and 1:1 respectively, 75.34U as the highest FPA can be acquired. Compared with other reports, the whole enzyme activity of the cellulase system had been improved. And the result can be an academic base of utilization of cellulose.