Study On The Screening Of Cellulose Degrading Bacteria And Their Fermentation Conditions

Cellulose is the most abundant organic material with most extensive source in nature, and is the most important renewable resource on the Earth. In our country, plant cellulose is resourceful, but most is burned and abandoned, causing serious environmental pollution. A large number of studies have shown that bio-degradation of cellulose overwhelms other methods when cellulose is decomposed or transformed into small-molecule compounds or other nutrients. So screening of cellulase-producing bacteria and studying of enzyme-production have important ecological benefit, economic effect and social significance.In this experiment, 97 bacterial strains with cellulose-decomposing capacity were screened from the soil of different regions, and fungal A-002 with a high cellulose degradation capability was obtained through re-screening. Strain A-002 was preliminarily identified as longibrachiatum (Trichoderma longibrachiatum), with the help of the morphology, ITS sequence alignment and phylogenetic analysis.Study on the enzymatic properties of Trichoderma longibrachiatum revealed that the optimum catalytic temperature of strain's CMCase and FPAase were 60 and 70℃, respectively; the optimum catalytic pH value of strain's CMCase and FPAase were 5.0 and 7.0, respectively. Cobalt ions, copper ions and ferrous ions had enhancing effect on the strain's CMCase. Through the study of optimum growth conditions, it showed that the optimal initial pH value for substrate was 3, with cultivation for 3 days at 37℃; the best liquid volume of 250mL flask fermentation was 100mL; a combination with peptone and ammonium nitrogen was the best nitrogen source; the sole carbon source of natural plant cellulose combination with grass stems was the best carbon source; such as PEG-8000 had enhancing effect on the strain's enzyme-producing; addition of small amount of Fe2 + was helpful to improve the enzyme-producing capacity of the strain. Study of the influence from natural plant fiber samples and each component on the enzyme-producing capacity of the strain showed that CMCase activity and FPAase activity were highest by using fermentated dicranopteris dichotoma and fermented bamboo reed as substrate, respectively; the cellulose content and the starch content in each component had the greatest impact on CMCase yield and FPAase yield, respectively.