Amino acid-induced inhibition and stimulation of Saccharomyces carlsbergensis. I. Variations in the response to pantothenic acid induced by casein hydrolysate.

The response pattern of Saccharomyces carlsbergensis (ATCC 9080) to pantothenic acid in Atkin's medium was changed dramatically by adding small amounts of casein hydrolysate (0.032 to 0.32 mg/ml) to the assay medium. Under static, mildly anaerobic conditions, growth at low pantothenic acid levels was reduced by 54 to 69%, whereas at saturating or near saturating pantothenate concentrations marked stimulation of growth (up to 41%) was observed. Under aerobic conditions, inhibition but not stimulation of growth occurred. It is recommended that Atkin's medium for the assay of pantothenic acid with S. carlsbergensis (ATCC 9080) be modified to include 0.6% acid-hydrolyzed casein (Vitamin Free Casamino Acids, Difco) to prevent erroneous growth responses, which may result if significant amounts of amino acids are present in natural materials being assayed for this vitamin.