Process And Mechanism Of Enhancing Nanringinase Fermentation By Heat Shock Via Aspergillus Niger

Naringinase has high commercial value,which expresses activity on both?-L-rhamnosidase and?-D-glucosidase.It is mainly obtained by microbial fermentation.However,the industrial development of naringinase is limited due to low production capacity and expensive cost.Heat shock is an effective strategy to promote the production of enzymes and related metabolites.A sudden increase in temperature may enhance the activity or yield of the enzyme involved.But there are few reports about the effects of heat shocking improving naringinase activity in Aspergillus niger fermentation pcocess.Based on initial strain screening and optimization of fermentation process,the optimized parameters of heat-shock strategy on fermentation process were further investigated.In addition,the organic acid of fermentation broth was analyzed and the mechanism of heat shock for improving naringinase activity was preliminarily explored at the molecular level.The main results are as followed:1.The strain of Aspergillus niger FFCC uv-11 was determined as the comfortable strain for producing naringinase,and the fermentation parameters were optimized as fermentation time of 120 hours,inoculation volume of 10%,initial pH of 6.0 and naringin as carbon source,and the naringinase fermentation activity was 765.85 U·mL^-1.2.It was investigated that the optimized parameters of heat-shock strategy on fermentation process were temperature of 35?,30 h for 30 min,and the number of heat shock was one time,and the nariginase fermentation activity reached 970.09 U·mL^-1,which was 1.27 times that of the non-heat-shock condition.3.The gene expression of?-L-rhamnosidase in different fermentation conditions was detected by Real-time PCR.The result showed that the level of?-L-rhamnosidase?RHA?expression with single heat shock was higher than those of other conditions.At the same time,RHA expression level and naringinase activity were positively correlated.It can be inferred that heat shock treatment mainly influences the expression of?-L-rhamnosidase gene,which can affect the synthesis of naringinase by Aspergillus niger.