The present invention relates to a coupled biotransformation process of converting chenodeoxycholic acid (CDCA) and related compounds to ursodeoxycholic acid (UDCA) and related compounds. It also relates to the cloning, expression, and biochemical characterization of a novel NADP.sup.+-dependent 7α-hydroxysteroid dehydrogenase (7α-HSDH) from Clostridium difficile, cofactor switch mutants thereof, and their application for the oxidation of bile acids. A further aspect of the invention relates to novel NADP-dependent cofactor switch mutants of the NADP.sup.+-dependent 7α-HSDH of E. coli and their application for the oxidation of bile acids.

The invention relates to novel 7β-hydroxysteroid dehydrogenase mutants, to the sequences which code for these enzyme mutants, to processes for the preparation of the enzyme mutants and to their use in enzymatic conversions of cholic acid compounds, in particular in the preparation of ursodeoxycholic acid (UDCA); subject-matter of the invention is also novel processes for the synthesis of UDCA using enzyme mutants; and the preparation of UDCA using recombinant, multiply modified microorganisms.

One aspect of the invention provides a nucleic acid encoding a 7β-hydroxysteroid dehydrogenase (7β-HSDH) that catalyzes at least the stereospecific enzymatic reduction of a 7-ketosteroid to the corresponding 7-hydroxysteroid. The enzyme includes a mutation at position 64 of SEQ ID NO:2 or in the corresponding sequence positions of an amino acid sequence derived therefrom with at least 90% sequence identity to SEQ ID NO:2. The mutation at position 64 is the mutation R64X.sub.1, wherein X.sub.1 represents E, D, T, L, S, P, V, K, C, A, G, Q, F, W, I or Y. The enzyme shows the following property profile in comparison with the 7β-HSDH with SEQ ID NO:2: (a) an increased specific activity (Vmax [U/mg]) for NADPH in the enzymatic reduction of dehydrocholic acid (DHCA) with NADPH as cofactor.

The present invention relates to methods and compositions for reducing the risk and severity of vancomycin-resistant Enterococci infection or colonization. It is based, at least in part, on the discovery that a restricted fraction of the gut microbiota, including the bacteria Clostridium scindens and/or the bacteria Blautia producta contribute substantially to resistance against vancomycin-resistant Enterococci infection or colonization. Without being bound by any particular theory, it is believed that this is achieved through the biosynthesis of secondary bile acids in the case of Clostridium scindens.

The present invention belongs to the field of bioengineering technologies, and in particular, to a production method of recombinant Escherichia coli (E. coli) and high-purity ursodeoxycholic acid (UDCA). The present invention constructs novel double-enzyme co-expression gene engineered bacteria, that is, recombinant E. coli. The bacteria simultaneously expresses 7β-hydroxysteroid dehydrogenase (7β-HSDH) and glucose dehydrogenase (GDH). The bacteria is applicable to the production of high-purity UDCA. The yield of a target product is increased through the joint expression and application of 7β-HSDH and GDH. The production method of high-purity UDCA in the present invention is simple, generates a small amount of impurities in a production process, is a green process that satisfies environmental protection requirements, and has significant industrial application value.

The present invention relates to methods and compositions for reducing the risk and severity of vancomycin-resistant Enterococci infection or colonization. It is based, at least in part, on the discovery that a restricted fraction of the gut microbiota, including the bacteria Clostridium scindens and/or the bacteria Blautia producta contribute substantially to resistance against vancomycin-resistant Enterococci infection or colonization. Without being bound by any particular theory, it is believed that this is achieved through the biosynthesis of secondary bile acids in the case of Clostridium scindens.

In various aspects and embodiments, the invention provides a nucleic acid molecule comprising a nucleotide sequence encoding a 7β-hydroxysteroid dehydrogenase (7β-HSDH) mutant that catalyzes at least the stereospecific enzymatic reduction of a 7-ketosteroid to the corresponding 7-hydroxysteroid, wherein the mutant has, compared to the wildtype 7β-HSDH of SEQ ID NO:2, a decreased substrate inhibition and/or an altered cofactor usage, and the mutant has, in comparison with the wildtype 7β-HSDH of SEQ ID NO:2, 1 to 15 amino acid additions, substitutions, deletions and/or inversions in the sequence motif VMVGRRE corresponding to positions 36 to 42 of SEQ ID NO:2.

The invention relates to novel 7-hydroxysteroid dehydrogenase mutants, to the sequences which encode these enzyme mutants, to processes for the preparation of the enzyme mutants and to their use in enzymatic reactions of cholic acid compounds, in particular in the preparation of ursodeoxycholic acid (UDCS). The invention also relates to novel processes for the synthesis of UDCS using the enzyme mutants; and to the preparation of UDCS using recombinant, multiply-modified microorganisms.

The present invention relates to methods and compositions for reducing the risk and severity of vancomycin-resistant Enterococci infection or colonization. It is based, at least in part, on the discovery that a restricted fraction of the gut microbiota, including the bacteria Clostridium scindens and/or the bacteria Blautia producta contribute substantially to resistance against vancomycin-resistant Enterococci infection or colonization. Without being bound by any particular theory, it is believed that this is achieved through the biosynthesis of secondary bile acids in the case of Clostridium scindens.

The present invention relates to a coupled biotransformation process of converting chenodeoxycholic acid (CDCA) and related compounds to ursodeoxycholic acid (UDCA) and related compounds. It also relates to the cloning, expression, and biochemical characterization of a novel NADP.sup.+-dependent 7-hydroxysteroid dehydrogenase (7-HSDH) from Clostridium difficile, cofactor switch mutants thereof, and their application for the oxidation of bile acids. A further aspect of the invention relates to novel NADP-dependent cofactor switch mutants of the NADP.sup.+-dependent 7-HSDH of E. coli and their application for the oxidation of bile acids.