The effects of glucose and potassium on the metabolism of pyruvate in Lactobacillus arabinosus

Abstract

Anaerobically, washed suspensions of L. arabinosus require glucose, KCl and MnCl2 for max. rates of pyruvate decomposition. The amt. of pyruvate utilized is accounted for by formation of CO2 and acetoin. Aerobically, different batches of cell suspensions differ in their Q02 values with pyruvate as substrate, the Q02 varying from 10 to 50. Cells with high Qo2 values require addition only of MnCl2 for the max. rates of pyruvate utilization; cells with low Q02 values require glucose, KCl and MnCl2 for full activity. Glucose acts catalytically, depresses 02 consumption and increases acetoin formation. KC1 is effective only in cells which also require glucose for max. activity. Fructose and galactase accelerate pyruvate utilization and increase acetoin formation, but less effectively than glucose. No acetoin is formed from sugars, glyceraldehyde, lactate or acetaldehyde; lactate and acetaldehyde do not increase acetoin formation from pyruvate. Pyruvate utilization is more rapid in citrate-phosphate buffers than in acetate buffers of the same pH; phthalate inhibits strongly. Aerobically, the pH optimum of the reaction is about 4.6, anaerobically about 3.7. Cell suspensions rapidly lose their ability to decompose pyruvate anaerobically without added glucose; the ability to decompose pyruvate aerobically, or anaerobicaliy in the presence of glucose, is retained for several days at 2[degree], especially when the cells are suspended in 0.1 MKCl.