Utilization of citrate by lactobacilli isolated from dairy products

Abstract

SummaryTwenty-five strains of lactobacilli isolated from dairy products, includingLactobacillus casei, Lactobacillus plantarumandLactobacillus brevisspecies, were grown in semi-defined media and examined for their ability to ferment citrate and produce formate. Of 7 strains ofL. casei, all utilized citrate to varying extents, as did 9 of 10 strains ofL. plantarumand 3 of 8 strains ofL. brevis.L. caseiproduced 19–35% of the theoretical yield of formate from the citrate utilized,L. plantarum0–11% andL. brevis0–28%. Of 2 strains ofL. caseitested for their abilities to ferment citrate in the presence of 2% lactose, strain C 5 was unaffected by lactose whereas strain C 2 showed a 45% decrease in the citrate utilized. However, lactose used at 2% concentration greatly reduced formate production byL. caseiC 5, which produced 62% of the theoretical yield of formate from citrate after 35 days in the absence of lactose and only 8% in its presence. The yield of diacetyl produced byL. caseiC 5 from citrate plus lactose (both at 2% concentration) was 145 times that produced from citrate alone, and 800 times that from lactose alone.