Citrate metabolism in Lactococcus lactis subsp. lactis var. diacetylactis strains

Publisher Website
Google Scholar
Abstract
The formation of diacetyl, acetoin, 2,3‐butylene glycol, acetaldehyde, ethanol and lactic acid during 24 h of cultivation in milk with 0.19 and 0.5 % of citrate has been studied. Depending on the strain, bacteria produced 1.5 ‐ 1.9 mg of diacetyl, 212 ‐ 311 mg of acetoin and 137 ‐ 156 mg of butylene glycol in 1 1 milk. An increase of the citrate concentration in milk to 0.5 % resulted in an increase in the production of diacetyl from 58 to 74 % and of acetoin by 2.8 ‐ 3.7 times. The strains of distinct activity of acetoin reductase produced in these conditions 2.3 ‐ 2.7 times as much as 2,3‐butylene glycol. The recovery of citrate in the from of C4‐compounds ranged from 76 to 98 %, yet barely 0.18 ‐ 0.44 % in the from of diacetyl. Increased concentration of citrate in milk stimulated the production of diacetyl and acetaldehyde to the similar extent, thereby it did not result in the deterioration of organoleptic qualities of starters and milk products. Within the doses used citrate did not significantly affect growth and acidifying activity of the bacteria.