Screening And Enzymatic Properties Of Pantoea Agglomerans Producing ?-galactosidase

?-galactosidase is an enzyme that eliminates antinutrient factors in legumes and improves nutrient utilization by decomposing the non-reducible terminal of sugar molecule.It can hydrolyze molasses directly,so it is also called meldiese.In this paper,microorganisms producing?-galactosidase were screened and isolated from different samples in order to find more?-galactosidases with different enzymatic properties.A strain of bacteria producing?-galactosidase was isolated from sufu.The conditions of producing?-galactosidase and its enzymatic properties were studied.The main experimental contents and results were as follows:?1?According to the characteristic that X-?-Gal can produce blue substance under the catalysis of alpha-galactosidase,a strain with high?-galactosidase production ability was screened out from tofu by using it as an indicator,named GK.The strain GK was identified as Pantoea agglomerans by 16S rDNA,physiological and biochemical experiments.?2?The growth conditions and enzymatic production conditions of strain GK were studied.It was found that the optimum growth pH of strain GK was 6.5 and the optimum growth temperature was 25?.The optimum conditions for enzymatic production were initial pH 7.0 of medium,250 mL/500 mL of liquid,culture temperature 20? and culture time 15h,and the enzyme activity was 14.07U/mL.According to the experimental results of each single factor,orthogonal experiments were carried out to analyze the interaction among the factors,in order to find the best culture conditions and enzyme production conditions of the strain.The results showed that the order of influencing factors of strain GK growth was temperature>pH>volume of liquid;the order of influencing factors of strain GK enzyme production was temperature>volume of liquid>pH.?3?The enzymatic properties of?-galactosidase produced by strain GK were studied.It was found that the optimum reaction pH of the enzyme was 7.0,the optimum reaction temperature was 43?,and the enzyme activity was stable under the acidity-basicity conditions of 45? and pH 5.0-8.0,and remained basically unchanged within 5h.Zn²⁺,Cu²⁺,Ca²⁺,Ag⁺inhibited the activity of the enzyme obviously,and basically completely inhibited the activity of the enzyme;K⁺and Na⁺had no significant effect on the activity of?-galactosidase;while EDTA could obviously promote the activity of the enzyme,after 24h,the activity of the enzyme reached 350% of the activity of the control enzyme.