Mutation And Characterization Of Isomaltulose High-producing Strain

Isomaltulose is composed of glucose and fructose by ?-1,6-glycoside linkage.Isomaltulose possesses many physiological functions and can be used as healthy food additives and an alternative to sucrose in food industry.At present,the production of isomaltulose has encountered many bottlenecks,such as the low isomaltulose yield due to the lower sucrose isomerase activity of the strain,and the high cost for product separation caused by the high viscosity of fermentation broth.Therefore,screening a strain with high sucrose isomerase activity,low viscosity of fermentation broth and high flocculation rate is of great significance to improve the productivity and reduce the production cost of isomaltulose.An isomaltulose producing strain Klebsiella sp.LX3 was isolated in our previous work.The strain LX3 had relatively high isomaltulose productivity.The sucrose isomerase produced by LX3 could catalyze the conversion of sucrose to isomaltulose,with a small amount of terhalulose by products,and almost no glucose and fructose were produced.In order to further improve the sucrose isomerase activity of LX3 strain and increase the yield of isomaltulose,Klebsiella sp.LX3 was used as the starting strain for mutation.The strain was mutagenized by atmospheric and room temperature plasma(ARTP)injection technique and the targeting isomaltulose high producing strain named LX3-1 was screened by comparing sucrose isomerase activity and isomaltulose production.The results showed that the sucrose isomerase activity of LX3-1 was increased by 20.42%(P<0.05),and the yield of isomaltulose was increased by 41.87%compared with wild strain LX3.At the meantime,the flocculation rate of LX3-1 was increased by 6.9%and the purity of isomaltulose was significantly increased.The yield of sucrose isomerase and isomaltulose was still stable after 6 generations of propagation.The sucrose isomerase-encoding gene sequence in the mutant strain did not undergo any mutations by obtaining the sucrose isomerase-encoding gene in the mutant strain LX3-1 and sequence alignment of the corresponding genes of wild-type strain.The reasons for the increase of enzyme activity might be that the components of regulating the sucrose isomerase were mutated.This work laid the foundation for improving the productivity and reducing the industrial production cost of isomaltulose.