Method of preparing tauroursodeoxycholic acid by biotransformation and application of method

The invention discloses a method of preparing tauroursodeoxycholic acid by biotransformation and application of the method. Biotransformation includes genetic codon optimization, engineered bacteria construction, engineered bacteria cultivation, substrate transformation and product preparation. Tauroursodeoxycholic acid is prepared by transforming a substrate through direct fermentation of engineered bacteria; the substrate is taurochenodeoxycholic acid. The substrate may reach 250 g/L in concentration; the reaction time is short; substrate transformation rate reaches 98% and above; the obtained product reaches 99% and above in purity; cyclic regeneration of NAD+ (nicotinamide adenine dinucleotide +) in the reaction system helps greatly reduce the usage of the coenzyme NAD+; the cost of enzymic catalytic reaction is reduced; industrial amplification is benefited. hydroxysteroid dehydrogenase and the regenerated coenzyme are connected via a flexible polypeptide sequence to form a protein fusion polymer; bindin