The effect of inorganic phosphate on the production of non-volatile, aliphatic organic acids by Aspergillus wentii.

Abstract

Inorganic phosphate has long been known to affect organic acid production and the types of acids produced are related to its concentration. In this study the effect of the variation of inorganic phosphate concentration on the production of non-volatile, aliphatic organic acids by a fungus was investigated. To find a suitable test organism 200 soil samples were taken and 306 acid producing specimens were isolated from them. Aspergillus wentii from these isolates was selected because of its ability to produce large amounts of several organic acids and its cultural characteristics. In A. wentii cultures having low phosphate concentrations (0.025 and 0.05 g phosphate/l) citric acid production was initiated first, while in the higher phosphate concentrations (0.5 and 1.0 g phosphate/l) malic acid was produced first. Another effect of phosphate concentration was the retardation of weight accumulation in the cultures having low phosphate concentrations. An event not related to phosphate concentration was the decrease of disappearance of malic acid after growth became limited in'a culture, which coincided with fumaric acid initiation.