Optimization of γ-PGA production from strain YW-5 and the effect of fermentation broth on cold tolerance of soybean
γ-Polyglutamic acid (γ-PGA) is a non-toxic water-soluble polyamino acid produced by microbial fermentation in nature. It is a kind of polymer formed by the condensation of L-glutamic acid and D-glutamic acid through dehydration. It has the characteristics of good ductility,biocompatibility,stability and water absorption.In this experiment,γ-PGA producing strains were isolated from fermented soybean products produced in the laborato-ry by screening media,and the strains were identified by morphological observation,physiological and biochemical identification and 16S rRNA sequence analysis. The fermentation conditions were optimized by single factor test and orthogonal test. In order to improve the low temperature tolerance of soybean seedlings,the gamma-PGA fer-mentation solution of the strain was applied in soybean pot,and the effect of the fermentation solution on the cold tolerance of soybean seedlings was preliminatively investigated.The results showed that a γ-PGA producing strain was isolated,named YW-5,belonging to Bacillus velezensis. The optimal fermentation conditions were 4 g·L-1 su-crose,1 g·L-1 beef paste,3.5 g·L-1 monosodium glutamate,0.03 g·L-1 potassium dihydrogen phosphate and 5.2 pH. After optimization,the yield of γ-PGA was 5.10 g·L-1. Pot experiment preliminatively proved that leaf spraying fer-mentation liquid can effectively reduce the MDA content of soybean seedlings under low temperature stress,in-crease the POD and CAT activities of soybean seedlings,and enhance the root vitality of soybean seedlings,which has good application potential.
γ-PGAsoybeanfermentation culture and optimizationlow temperature stressBacillus velezensisMDAroot activity
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