Screening Of High Efficient Cellulose Decomposing Bacteria And Theirs Embedding Immobilization

In recent years,with the shortage of resources and environmental pollution problems have been increasing,as a renewable biomass resource,the processing and utilization of straw fiber is not only related to the development of new resources and to alleviate the shortage of resources but also related to the rural ecological protection and new rural construction.So straw returning to the field as the most environmentally friendly,the highest utilization rate of treatment has been widespread concern at home and abroad.With the continuous development of molecular biology,straw return to the field from the traditional way of burning and mechanical crushing more and more biased in adding the cellulose microbial agent to the straw to promote the decay of the straw and speed up the degradation of the straw cellulose.The method not only can cause environmental pollution,but also can improve soil fertility and improve soil structure.At present,there have been thousands of strains screened from the soil,but the overall degradation capacity is relatively simple,and the degradation effect is general.Therefore,screening efficient cellulose decomposing bacteria plays the most important part in the degradation of cellulose.This experiment is based on the purpose of obtaining high efficient cellulose decomposing bacteria.Through isolation and purification,30 strains were obtained preliminarily.Preliminary screening by Congo red dye method yielded 14 strains of cellulolytic bacteria,and further screening through filter paper disintegration test yielded 5 strains of relatively effective cellulolytic bacteria.With straw and bran as carbon source,5 strains were screened for continuous5 d fermentation culture The CMCase activity and FPA activity were measured by DNS staining at every 24 h.Finally,4 strains of cellulose decomposing bacteria were determined and named X-1,X-6,X-7 and X-11 respectively.These 4 strains of cellulose decomposing bacteria's enzyme production ability were determined,the CMCase activities of 4 strains were higher,respectively71.17 U/m L,57.48 U/m L,65.96U/m L and 69.2 U/m L;FPA activity of Strains X-6 and X-11 were the lowest and the highest,enzyme activity can reach 34.17 U/m L and 53.41 U/m L respectively;The ?-Gase activity of strain X-11 was the highest,74.43 U/m L,and strain X-7 had the lowest?-Gase activity and reached 35.79 U/m L.On the whole,4 cellulose decomposing bacteria screened have high enzyme production ability.and Then the 4 strains of dominant cellulolytic bacteria were used in the solid and liquid fermentation of straws.During 30 d fermentation,compared with solid-state fermentation under natural conditions,The degradation rate of straw were increased by28.92%,30.40%,30.33% and 37.99%;with the natural state of liquid fermentation,thedegradation rate of straw were increased by 31.92%,40.15%,35.29%.The results showed that the4 strains had relatively high capacity for degrading straw cellulose.The strain X-11 was used as an example to be immobilized by sodium alginate embedding method.Determined by orthogonal experiments,when the embedding medium concentration was5%,fixing agent concentration was 5%,the ratio of embedding medium and bacteria liquor was2:1 and crosslinking time was 24 h,the mobilized bacteria bead had a optimal quality.The growth kinetic model and substrate consuming kinetic model of mobilized bacteria were built using Origin8.0 software,according to the Logistic equation and Luedeking-Piret equation,and explored the future application of immobilized microorganism technique in the field of cellulose degradation preliminary.Molecular identification of the 4 dominant bacteria strains,according to 16 Sr DNA sequence alignment results showed that strains X-1,X-7 and X-11 belong to the Alcaligenes faecalis;strain X-6 belongs to the Pseudochrobactrum saccharolyticum.The study on the application of this genus to the degradation of cellulose is less.The results of this study provide a theoretical basis and important significance for the study of the application of this genus.