Growth characteristics of lactic acid-producing strains using glucose syrup as a carbon source

Abstract

This work investigates the growth and productivity characteristics of such lactic-acid producing strains, as Lactobacillus delbrueckii subsp. bulgaricus 19-11 (VKPM B-2368), Lactobacillus acidophilus 5 Ds (VKPM B-2846) and Lactococcus lactis subsp. lactis (VKM B-1662) on standard MRS medium using glucose syrup as a carbon substrate. According to the results of batch cultivation of the selected strains in 5L fermenters for 72 h, the productivity was established to decrease in the Lactobacillus delbrueckii subsp. bulgaricus 19-11 > Lactobacillus acidophilus 5 Ds > Lactococcus lactis subsp. lactis series. L. delbrueckii subsp. bulgaricus 19-11 showed the maximum lactic-acid productivity of 1.94 g/(l×h) with a glucose conversion degree of 87%. After cultivation, a slight decrease in the content of nitrogen, potassium and sodium in the culture liquid of the studied strains was observed. In all strains, the content of other macronutrients (phosphorus, calcium, sulphur, magnesium, barium and iron) increased in proportion to the addition of glucose syrup during cultivation, which is directly related to their significant content in its composition. The Lactobacillus delbrueckii subsp. bulgaricus 19-11 and Lactobacillus acidophilus 5 Ds strains produced racemic (DL) lactic acid, whereas Lactococcus lactis subsp. lactis produced lactic acid with a 73% L-isomer content. The use of glucose syrup in biotechnological processes can contribute to the implementation of waste-free production in the respective enterprises.