The wild-type Xanthomonas maltophilia was chosen as the starting strain,and the inclusion complex of chenode-oxycholic acid and β-cyclodextrin was adopted as the reaction substrate.On the basis of the 7α-hydroxysteroid dehydrogenase and 7β-hydroxysteroid dehydrogenase generated during the liquid culture process of Xanthomonas maltophilia,the whole-cell systems were utilized to produce ursodeoxycholic acid and intermediates via enzymatic conversion means.The morphology of Xanthomonas maltophilia was identified,enzyme activity was determined and conditions were optimized.A standard detection method for transformation products was established using high performance liquid chromatography method(HPLC).The trans-formation conditions were optimized by single factor experimental design.Morphology identification showed that Xanthomonas maltophilia was a rod-shaped,monoflagellated,gram-negative bacterium.After the cell disruption of the culture,SDS-PAGE analysis indicated that there was a protein band between 26-33 kDa.The enzyme activities of 7α-hydroxysteroid dehydrogenase and 7β-hydroxysteroid dehydrogenase were of 79 U/mL and 35 U/mL,respectively.The optimization results showed that the en-zyme activity increased when the temperature was 35 ℃,pH value was 9.0 and 30％methanol was added.The yield of UDCA and 7K-LCA were 17.2 mg/L and 18.2 mg/L respectively.As a wild-type chassis-transformed strain,this study provides a new pathway for the whole-cell catalytic production of ursodeoxycholic acid and its intermediates.
维普
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