Organic acid metabolism of Penicillium chrysogenum. 1. Lactate and acetate

Abstract

Lactate and acetate are oxidized by growing cultures and washed, starved mycelial suspensions of P. chrysogenum. Mycelial suspensions oxidize lactate only in the presence of 02, and the opt. pH is in the range 4.0 to 6.0. In the presence of arsenite, half max. velocity of lactate oxidation occurs at a substrate concn. of 2 x 10-4 [image]. The 1st product of lactate oxidation is pyruvate. This is reduced back to lactate in presence of glucose. Lactate is not formed from glucose alone. The QO2 (lactate) was inhibited by both arsenite (0.01 [image]) and iodoacetate (0.001 [image]); these compounds also inhibit the QO2 (pyruvate). Malonate, streptomycin, methylene blue or 2:4-dinitrophenol had no effect on the QO2 (lactate). Prolonged aerobic incubation of mycelium with factate under specified conditions leads to the accumulation of considerable amounts of pyruvate and alpha-oxoglutarate. Acetate, citrate and glutamate under the same conditions give very low yields of ketonic products. Succinate, malate and fumarate give intermediate amts. of keto acids, all much less than lactate. All these acids increase O2 uptake by mould mycelium. Acetate utilization, unlike that of lactate, is rapid in presence of glucose. Acetate oxidation by mycelium is maximal between pH 6 and 7. The rate of oxidation of acetate is half max. at an acetate concn. of 1.2 x 10-3 [image]. The Q02 (acetate) is depressed by arsenite (0.01[image]), iodoacetate (0.001[image]), and azide (0.003[image]). Malonate, streptomycin and methylene blue do not inhibit. Acetate causes mycelium to "waste" on prolonged incubation, whereas lactate tends to conserve mycelial dry matter.