Some aspects of (-)-citramalic acid accumulation by respiration-deficient mutants of yeasts.

Abstract

A comparative study of the organic acid productivities of respiration-competent (normal) and respiration-deficient (RD) strains of brewers' yeasts (Saccharomyces carlsbergensis) was made using a chemically defined medium containing 5% glucose. After growing for 6 days, lactic and an unknown acids were mainly accumulated by RD-mutants, while acetic, succinic and lactic acids were the major acids accumulated by the normal strains.The unknown acid was then isolated in a pure form by repeated silica gel chromatography and was identified as (-)-citramalic acid by elemental analysis, IR and NMR spectra, and rotation measurement. (-)-Citramalic acid was also accumulated by RD-mutants in other media, and the ratio of (-)-citramalic acid to the total amount of organic acids produced was almost constant (32-39%), even when the amount of citramalic acid increased by increasing glucose concentration or by the addition of calcium carbonate to the media.