Screening And Optimization Of Fermentation Conditions For Cellulase Production By Bacillus

Cellulose is the most original and the largest amount of storage of natural compounds,which is the most precious and cheap renewable resources.More than half of it have been burned or discarded directly in the fields every year in Chain,which caused great waste of resources,also environmental pollution at the same time,which harmed to human health.Therefore turning the waste of agricultural resources into valuable material has received attention.According to a study,cellulose by enzymatic degradation have obvious advantages.Now the application of cellulase in industries has produced many achievements,such as it have made tremendous benefits of the application in food,fermentation industry and environmental protection.A large number of researchs found that many biological can produce cellulase,and to prepare a large number of cellulase,and the most effective method is the use of microbial fermentation.The Bacillus is spherical or rod-shaped bacteriacan which can form spores(endospores),which resistance to external harmful factors.They are widely distributed,and exist in soil,water,air and animal intestines.It has a higher heat resistance,more suitable for fermentation.It has become an important research direction in the study of cellulase producing microorganisms in China,and methods and technology are relatively mature.The purpose of this paper is to enrich and select cellulose degrading Bacillus which produce cellulose enzyme,and then to separate and identify it.Carrying on systematic researches on the cultivation conditions and fermentation characteristics to the screened high activity strains.After high temperature treatment,20 strains of Bacillus were screened and cultured on the medium with sodium carboxymethyl cellulose as carbon source,and after 48 h,at about 30?.Be based on morphological,physiological and biochemical,molecular biological identification,strain JD2 is Bacillus amyloliquefaciens,strain JK1 is Bacillus velezensis,strain JK5 is Bacillus nematocida,strain JK7 is Bacillus subtilis,strain JK9 is Bacillus cereus.The enzyme activity of the strain JK7 was the highest,and the enzymatic properties of strain JK7 were further studied,show that the optimum temperature of cellulase produced by strain JK7 is 50 ?,the optimum pH5.0,the optimum carbon source for corn straw(30 g/L),the optimum nitrogen source was soybean meal(10 g/L),and had a good thermal stability.On this basis,in order to optimize the fermentation conditions,the enzyme activity was higher,preliminary study on influencing factors of fermentation,which determine the influence factors as the optimization conditions,analysis of the experimental step,using Box-Behnken Design(BBD)design method of response surface optimization test,find out the optimization of culture conditions of combination of JK7 strains.The use of Design-Expert.8.0.5 software,the experimental results drawn into 3D graph,optimized condition of enzyme optimum fermentation:initial pH6.91,237 rpm speed,temperature is 35.3?.Under the optimal fermentation conditions,the cellulase activity was up to 12.16 U/mL,which was 6.85 times higher than that of the original enzyme.