Co‐metabolism of citrate and glucose by Leuconostoc spp.: effects on growth, substrates and products

Growth, substrate utilization and product formation from glucose, citrate and a mixture of both substrates were studied in four strains of Leuconostoc spp. Citrate was not used as an energy source but was rapidly metabolized when glucose was present. The predictable amounts of D‐lactate and ethanol were produced from glucose, although strains X2 and 7–1 gave lower yields of ethanol. In strains NCW1, S3 and X2, co‐metabolism of both glucose and citrate resulted in stimulation of growth, decreased uptake of glucose, increased acetate and D‐lactate production and lack of ethanol production compared with that obtained with glucose alone. Strain 7–1 showed only growth stimulation and increased acetate production. Diacetyl, acetoin or 2, 3‐butylene glycol were not detected. In strain NCW1 citrate had a slightly inhibitory effect on the enzymes of the ‘ethanol’ leg of glucose metabolism. Except for strain 7–1, these observations are consistent with a switch in glucose metabolism from ethanol to acetate production.