Identification and Characterization of Some Genes, Enzymes, and Metabolic Intermediates Belonging to the Bile Acid Aerobic Catabolic Pathway from Pseudomonas

The study of the catabolic potential of microbial species isolated from different habitats has allowed the identification and characterization of bacteria able to assimilate bile acids and/or other steroids (e.g., testosterone and 4-androsten-3,17-dione) under aerobic conditions through the 9,10-seco pathway. From soil samples, we have isolated several strains belonging to genus Pseudomonas that grow efficiently in chemically defined media containing some cyclopentane-perhydrophenanthrene derivatives as carbon sources. Genetic and biochemical studies performed with one of these bacteria (P. putida DOC21) allowed the identification of the genes and enzymes belonging to the route involved in bile acids and androgens, the 9,10-seco pathway in this bacterium. In this manuscript, we describe the most relevant methods used in our lab for the identification of the chromosomal location and nucleotide sequence of the catabolic genes (or gene clusters) encoding the enzymes of this pathway, and the tools useful to establish the role of some of the enzymes that participate in this route.

Identification and Characterization of the Genes and Enzymes Belonging to the Bile Acid Catabolic Pathway in Pseudomonas

The study of the catabolic potential of microbial species isolated from different habitats has allowed the identification and characterization of bacteria able to assimilate bile acids and other steroids (e.g., testosterone and 4-androsten-3,17-dione). From soil samples, we have isolated several strains belonging to genus Pseudomonas that grow efficiently in chemical defined media containing some cyclopentane-perhydro-phenantrene derivatives as carbon sources. Genetic and biochemical studies performed with one of these bacteria (P. putida DOC21) allowed the identification of the genes and enzymes belonging to the 9,10-seco pathway, the route involved in the aerobic assimilation of steroids. In this manuscript, we describe the most relevant methods required for (1) isolation and characterization of these species; (2) determining the chromosomal location, nucleotide sequence, and functional analysis of the catabolic genes (or gene clusters) encoding the enzymes from this pathway; and (3) the tools employed to establish the role of some of the proteins that participate in this route.

Production of 4-androstene-3,17-dione and 1,4-androstadiene-3,17-dione from rice germ and wheat germ extracts by Mycobacterium sp

OBJECTIVE

To study the biotransformation of phytosterol and phytosterol-containing rice germ and wheat germ ethanolic extracts to produce 4-androstene-3,17-dione (AD) and 1,4-androstadiene-3,17-dione (ADD) by Mycobacterium sp. DSM 2966 using phytosterol to hydroxypropyl-β-cyclodextrin (2:1, 1:1 and 1:2 mol/mol) and 2 % (w/v) Tween 80 as solubilizing agents.

RESULTS

A maximum yield of 180 ± 27 mg AD l(-1) and 31 ± 11.4 mg ADD l(-1) with a total conversion of 65 % (day 12) was obtained using 1 g phytosterol l(-1) and hydroxypropyl-β-cyclodextrin (2 : 1 mol/mol) with 2 % (w/v) Tween 80 in the fermentation medium. The most appropriate conditions for rice germ extract and wheat germ extract which gave the maximum conversion of 22 and 43 % (day 14) were obtained by using 2 % (w/v) Tween 80.

CONCLUSIONS

Phytosterol and wheat germ are effective sources for AD and ADD production while rice germ required further development. Hydroxypropyl-β-cyclodextrin (2 :1 mol/mol) and/or 2 % (w/v) Tween 80 in the biotransformation process could improve AD and ADD yields, depending on substrates and biotransformation conditions.