Isolation And Identification Of Termitomyces Eurrhirzus And Optimization Of Liquid Fermentation Conditions For Exopolysaccharide Production

Termitomyces eurrhirzus is a kind of wild edible and medicinal fungi with rich nutrition and medicinal value.It is also one of the traditional Chinese medicinal fungi.It contains polysaccharides,polyphenols,saponins and other active substances.It has the effects of anti-oxidation,anti-inflammatory,anti-tumor,hypoglycemic and repairing liver injury.At present,the active components of Termitomyces eurrhirzus are mainly extracted from the fruiting body,which has the problems of long production cycle and complicated technology.In this paper,the mycelium culture was obtained by tissue isolation from the fruiting bodies of suspected wild Termitomyces eurrhirzus.The optimum medium composition and fermentation conditions of exopolysaccharide yield by liquid fermentation of Termitomyces eurrhirzus were studied by single-factor test,and the factors affecting the yield of EPS were optimized by response surface experiments.The main results were as follows:（1）The pure strain ZZJ-1 was obtained from the fruiting bodies of suspected wild Termitomyces eurrhirzus collected in the field by tissue isolation method.Based on the observation of colony and mycelium morphology,ITS rDNA sequence analysis and phylogenetic tree construction,the strain was identified as ZZJ-1.（2）Effects of medium composition and fermentation conditions on the exopolysaccharide yield were studied by single-factor experiment.The results showed that the optimal fermentation medium was:maltose 6%,yeast extract 1.5%,KH₂PO₄0.1%,MgSO₄·7H₂O 0.05%,VB1 10 ppm/L;the optimal fermentation conditions were:fermentation temperature 30℃,initial pH 6.5,inoculum 6%（V/V）,seed age 5days,liquid loading 150 mL/300 mL flask,shaking speed 170 r/min,fermentation time 6 days.Under these conditions,the yield of EPS was 647.27μg/mL.（3）The fermentation medium and fermentation conditions were optimized by response surface experiments based on the results of single factor experiment,and the antioxidant activity of EPS was studied.The results showed that the optimal fermentation medium was:maltose 6.13%,yeast extract 1.42%,KH₂PO₄ 0.112%,MgSO₄·7H₂O 0.056%,VB1 10ppm/L.Under these conditions,the average yield of EPS was 513.38μg/ml,and the relative error was 1.4720%.The fermentation conditions were:Seed Age 122 h,liquid volume 150 mL/300 mL,fermentation time166 h.Under these conditions,the average yield of EPS was 671.57μg/mL,and the relative error was 1.78%.The results showed that the regression model could be used to predict the production of exopolysaccharide.This study is of great significance for the liquid fermentation of Termitomyces eurrhirzus to produce exopolysaccharides,and provides a new idea for the deep development of Termitomyces eurrhirzus,which has good application value.