Production of a pharmaceutical intermediate via biohydroxylation using whole cells of Rhodococcus rubropertinctus N82

Construction of Rhodococcus expression vectors and expression of the aminoalcohol dehydrogenase gene in Rhodococcus erythropolis

NADP+-dependent aminoalcohol dehydrogenase (AADH) of Rhodococcus erythropolis MAK154 produces double chiral aminoalcohols, which are used as pharmaceuticals. However, the genetic manipulation of Rhodococcus strains to increase their production of such industrially important enzymes is not well studied. Therefore, I aimed to construct Rhodococcus expression vectors, derived from the Rhodococcus–Escherichia coli shuttle vector pRET1102, to express aadh. The plasmid pRET1102 could be transformed into many actinomycete strains, including R. erythropolis. The transformation efficiency for a species closely related to R. erythropolis was higher than that for other actinomycete strains. Promoters of various strengths, hsp, 1200rep, and TRR, were obtained from Gram-positive bacteria. The activity of TRR was stronger than that of hsp and 1200rep. The aadh-expressing plasmid pRET1172 with TRR could be transformed into many actinomycete strains to increase their AADH production. The Rhodococcus expression vector, pRET11100, constructed by removing aadh from the pRET1172 plasmid may be useful for bioconversion.

Bioconversion of pyridoxine to pyridoxamine through pyridoxal using a Rhodococcus expression system

Pyridoxamine, which is a form of vitamin B₆, is a promising candidate for a prophylactic and/or remedy for diabetic complications. Pyridoxamine is chemically synthesized by an oxidative method in manufacturing. However, pyridoxamine production by bioconversion, which is generally preferable for environmental and energetic aspects, has been little investigated. Therefore, I aimed to produce pyridoxamine from pyridoxine, which is a readily and economically available starting material, by bioconversion using a Rhodococcus expression system. I found in the bioconversion of pyridoxine to pyridoxal, approximately 450 mM pyridoxal was produced from 500 mM pyridoxine using recombinant Rhodococcus erythropolis expressing the pyridoxine 4-oxidase gene derived from Mesorhizobium loti. Next, in the bioconversion of pyridoxal to pyridoxamine using recombinant R. erythropolis expressing the pyridoxamine-pyruvate aminotransferase gene derived from M. loti, the bioconversion rate was approximately 80% under the same conditions as pyridoxal production. Finally, in the bioconversion of pyridoxine to pyridoxamine through pyridoxal using recombinant R. erythropolis coexpressing the genes for pyridoxine 4-oxidase and pyridoxamine-pyruvate aminotransferase, the bioconversion rate was approximately 75%. Based on these findings, pyridoxamine production by bioconversion using a Rhodococcus expression system may be of interest for future industrial applications.