Screening And Identification Of Cellulose Degrading Strains And Optimization Of Degradation Conditions

Cellulose is the most original and most stored natural compound on earth,and the most extensive and abundant organic renewable resource in the world.However,due to its special structure,cellulose itself is not easily degraded and the utilization rate is extremely low.Turning substances with high cellulose content into valuable substances has received attention.Compared with physical and chemical degradation methods,the use of microbial degradation has obvious advantages.Now the application of cellulase in industries has produced many achievements,such as in the food industry,fermentation industry,and environmental protection industry.However,the efficient degradation of cellulose is always the key to restrict the application of biomass,In view of the current low and unstable viability of cellulose-degrading strains,which restricts the effective use of cellulose resources,Laboratory healthy mice and rice fish scraps from coastal areas is used as the strains resources in this experiment.The main content of this paper is to enrich and select cellulose degrading strains which produce cellulose enzyme,and then separate and identify it.And finally its fermentation enzyme production conditions are optimized,in order to improve its enzyme production capacity,to be widely used in later industrial production,and to provide theoretical basis and technical support for solving the development and utilization of cellulose resources.The main results of the paper are as follows.Healthy laboratory mice’s stomach and feces,freshwater fish and marine fish waste are chose as samples.After enrichment culture in the medium with kelp powder as the sole carbon source,the diluted bacterial solution is applied to carboxymethyl Cellulose sodium(CMC-Na)medium,cultured at 37 ℃ for 24 h,to obtain strains that can grow on the medium with CMC-Na as the sole carbon source.Strains with different morphological characteristics are picked and cultivated in three-zone streak culture on the CMC-Na medium which was used to isolate and purify the strains,and then 8 single strains were obtained.The three-point inoculation method was used for spot connection on cellulose Congo red medium,and the degradation circle was observed at 37 ℃ for 24 h.The ratio of the diameter of the degradation circle to the diameter of the strain was compared,and a strain with degrading ability was obtained by double screening.Be based on morphological observation,Gram staining experiment,and molecular biological identification,strain A6 is Aeromonas,and the phylogenetic tree of the strain was constructed.On this basis,the growth curve of the strains was drawn to understand the growth characteristics of the strains.The strains grew rapidly and reached maximum growth in the vicinity of 2~3 d.At the same time,the filter paper strip degradation experiment was designed to reflect that the strain has a certain degree degradability of natural cellulose.Finally,in order to optimize the fermentation enzyme production conditions and obtain higher enzyme activity,the optimal fermentation enzyme production conditions are obtained by taking carboxymethylcellulase activity(CMC-ase)and filter paper enzyme activity(FP-ase)as the measurement standards: Carbon source species CMC-Na and straw powder mixture,nitrogen source species peptone,initial pH 6,temperature is 37 ℃,culture time 3 d.Cultivated.Under the optimal enzyme-producing fermentation conditions,the CMC-ase and the FP-ase of the strains were measured to be 1.23 times and 1.65 times higher than the original enzyme activity respectively,and the degradation rate of straw could reach 60%.