Biosynthesis of Vitamin B6by a Yeast Mutant

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Abstract
The gradient-plate technique was employed to isolate mutants ofSaccharomyces marxianus(NRRL-Y-1550) which, when grown in a synthetic culture medium, excreted about 2 μg/ml of vitamin B6as ascertained by microbiological assay. The major component that possessed vitamin B6activity was isolated by ion-exchange column chromatography and identified as pyridoxol by ultraviolet and fluorescence spectroscopy, as well as by paper chromatography and various chemical tests. Pyridoxal was also identified as one of the excreted compounds. Two other compounds that possessed vitamin B6activity were excreted in smaller quantities in the growth medium and have not yet been identified; they are not phosphates of vitamin B6. The amount of vitamin B6excreted was not increased when the mutant was grown in the presence of various oxidation products of this vitamin. The methods and results reported here may be helpful in future studies on the biosynthesis of vitamin B6.