THE EFFECT OF AMINO ACIDS ON GROWTH AND SPORULATION OF ASPERGILLUS FLAVUS AND THEIR CARRY‐OVER FOR SUBSEQUENT SPORE GERMINATION

Abstract

Summary Aspergillus flavus utilized amino nitrogen source better than nitrate, nitrite, or ammonium nitrogen sources. With casein hydrolysate as nitrogen source, optimum growth was obtained at 100 μg N/ml concentration when incubated for 8 days at 24–26° C. Using ten different amino acids singly or in mixture in Czapek's synthetic basal medium at a concentration of 100 μg N/ml, the mycelial yields were higher when the basal medium contained L‐arginine, glycine, DL‐leucine, DL‐methionine or the mixture of ten amino acids, than when casein hydrolysate was used. Abundant sporulation was obtained when the basal medium contained glycine, DL‐leucine or DL‐methionine. Spores harvested from media containing single amino acids germinated very poorly, although spores harvested from media containing casein hydrolysate, when germinated in individual amino acids, showed good germination in β‐alanine, L‐arginine, glycine, DL‐leucine, DL‐methionine and L‐tryptophane. When one of the ten amino acids was omitted from the basal medium, growth response was poor when any of L‐arginine, glycine, DL‐leucine, or DL‐methionine were absent; germination of spores harvested from media devoid of β‐alanine, glycine, DL‐leucine, DL‐methionine or L‐tryptophane was significantly poor. The combination of one or more amino acids did not show any additive effect, but each amino acid seemed to act independently. The carry‐over effects of the amino acids reflected in subsequent spore germination was conspicuous with β‐alanine, glycine, DL‐leucine, DL‐methionine and L‐tryptophane. These five amino acids when used alone or in combination with each other in the basal medium, produced spores which germinated normally; L‐tryptophane seemed to be the most important amino acid among these, as its absence in the medium markedly affected spore germination.