Screening of Nitrocellulose Degrading Strain and Preliminary Study on Its Degradation Mechanism
Nitrocellulose was used as a screening medium,and six degrading strains with excellent growth were obtained by plate screening of the isolated strains after sampling and the strains stored in the laboratory.The nitrocellulose degrading strain TL06 was obtained by solid state fermentation and secondary screening.Through ITS sequence analysis and phylogenetic tree analysis,it was identified as Trichoderma simmonsii and named Trichoderma simmonsii TL06.The effects of medium components and culture conditions on cellulase and esterase activities of Trichoderma simmonsii TL06 were investigated.The results showed that the cellulase and esterase activities were significantly decreased by adding an organic nitrogen source into the medium,while the cellulase activity was significantly increased by adding an inorganic nitrogen source ammonium sulfate.Adding a carbon source significantly reduced cellulase activity but had no significant effect on esterase activity.In order to optimize the fermentation conditions,the orthogonal experiment was set up.It was found that the cellulase activity reached 1.36 IU/g under the conditions of ammonium sulfate concentration of 1.5%,mass ratio of nitrocellulose to bran of 5:5,fermentation time of 5 d,feed-to-water ratio of 10∶12,culture temperature of 30℃,and natural pH value,which was 189.36%higher than that before optimization.It was preliminarily discovered that the mechanism of Trichoderma simmonsii TL06 in degrading nitrocellulose was the secretion of cellulase and esterase and the hydrolysis of β-1,4 glucoside bond and nitrate bond,in which the hydrolysis of glucoside bond was preferentially initiated.
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