Ursodeoxycholic acid production by Gibberella zeae mutants

Improving Geldanamycin Production in Streptomyces geldanamycininus Through UV Mutagenesis of Protoplast

Geldanamycin, a benzoquinone ansa antibiotic, has been extensively applied in medical, agricultural, and health research areas due to its antitumor, antifungal, herbicidal, and antiradiation effects. In this study, an improvement of geldanamycin production by Streptomyces geldanamycininus FIM18-0592 was first performed by protoplasts combined with UV mutagenesis and ribosome engineering technology, respectively. The results showed that strains induced by UV mutagenesis of protoplasts were superior to protoplasts treated with erythromycin in terms of the positive variability, average relative titer, and maximum relative titer, with values of 51.95%, 99%, and 136%, respectively. A mutant strain that produced 3742 μg/mL geldanamycin was generated by protoplast UV mutagenesis, with a 36% higher yield than the initial strain. Multi-omic analysis revealed that the high-yielding geldanamycin in mutant strain 53 could upregulate GdmG and GdmX by 1.59 and 2.38 times in the ansamycin synthesis pathway, and downregulate pks12, pikAI, and pikAII by 0.25, 0.37, and 0.48 times in the fatty acid synthesis pathway, which was crucial for geldanamycin production. Our study provides a novel S. geldanamycininus geldanamycin production strategy and offers valuable insights for mutagenesis and breeding of other microorganisms.

A fungal P450 enzyme from Fusarium equiseti HG18 with 7β-hydroxylase activity in biosynthesis of ursodeoxycholic acid

Cytochrome P450 enzyme with 7β-hydroxylation capacity has attracted widespread attentions due to the vital roles in the biosynthesis of ursodeoxycholic acid (UDCA), a naturally active molecule for the treatment of liver and gallbladder diseases. In this study, a novel P450 hydroxylase (P450FE) was screen out from Fusarium equiseti HG18 and identified by a combination of genome and transcriptome sequencing, as well as heterologous expression in Pichia pastoris. The biotransformation of lithocholic acid (LCA) by whole cells of recombinant Pichia pastoris further confirmed the C7β-hydroxylation with 5.2% UDCA yield. It was firstly identified a fungal P450 enzyme from Fusarium equiseti HG18 with the capacity to catalyze the LCA oxidation producing UDCA. The integration of homology modeling and molecular docking discovered the substrate binding to active pockets, and the key amino acids in active center were validated by site-directed mutagenesis, and revealed that Q112, V362 and L363 were the pivotal residues of P450FE in regulating the activity and selectivity of 7β-hydroxylation. Specifically, V362I mutation exhibited 2.6-fold higher levels of UDCA and higher stereospecificity than wild-type P450FE. This advance provided guidance for improving the catalytic efficiency and selectivity of P450FE in LCA hydroxylation, indicative of the great potential in green synthesis of UDCA from biologically toxic LCA.

Biological synthesis of ursodeoxycholic acid

Ursodeoxycholic acid (UDCA) is a fundamental treatment drug for numerous hepatobiliary diseases that also has adjuvant therapeutic effects on certain cancers and neurological diseases. Chemical UDCA synthesis is environmentally unfriendly with low yields. Biological UDCA synthesis by free-enzyme catalysis or whole-cell synthesis using inexpensive and readily available chenodeoxycholic acid (CDCA), cholic acid (CA), or lithocholic acid (LCA) as substrates is being developed. The free enzyme-catalyzed one-pot, one-step/two-step method uses hydroxysteroid dehydrogenase (HSDH); whole-cell synthesis, mainly uses engineered bacteria (mainly Escherichia coli) expressing the relevant HSDHs. To further develop these methods, HSDHs with specific coenzyme dependence, high enzyme activity, good stability, and high substrate loading concentration, P450 monooxygenase with C-7 hydroxylation activity and engineered strain harboring HSDHs must be exploited.