<div><p>The microbial transformation of vitamin D<sub>3</sub> (<b>1</b>) by the fungi <i>Candida maltosa</i> R42 and <i>Botrytis allii</i> NRRL 2502 was investigated. Incubation of compound <b>1</b> with <i>C. maltosa</i> R42 and <i>B. allii</i> NRRL 2502 produced the same three more polar metabolites in small yields. The main metabolite was identified as 1α-hydroxyvitamin D<sub>3</sub> (<b>2</b>). This biotransformation has utility as a possible tool for the production of 1α-hydroxyvitamin D<sub>3</sub> from the readily available vitamin D<sub>3</sub> for patients with compromised kidney function.</p></div
