Biosynthetic activity study of Lactobacillus acidophilus lactic acid bacteria in the lactose fermentation of whey

According to numerous studies, lactic acid bacteria are characterised by the capability of reducing their initial activity given an insufficient quantity of growth factors supplied by a nutrient medium. Conversely, the introduction of additional sources of nutrient into the medium provides favourable conditions for the development of lactic acid-producing microorganisms. The present study was aimed at examining the effect of phosphorus-containing salts on the biosynthetic activity of a specially selected strain of lactic acid bacteria for the biotransformation of acid whey lactose into lactate-containing ingredients. For this purpose, lactic acid bacteria of the Lactobacillus acidophilus thermophilic bacilli subgroup applied in cheese and fermented dairy production were used as a producer of lactic acid. In the obtained fermented solutions, the mass fractions of lactose and calcium lactate were determined by the Bertrand method and complexometric techniques, respectively. The variables in the biosynthetic activity study of lactic acid bacteria included the type of phosphorus-containing salt (disodium phosphate dodecahydrate and disubstituted ammonium phosphate) and its mass fraction, which ranged from 1.0 to 3.0 % in increments of 0.5 %. The amount of inoculum introduced for maximum production of lactic acid comprised 2.5 % vol. of the nutrient medium. The titratable acidity of the inoculum ranged from 1.80 to 1.85 g/cm(3). In order to produce calcium lactate, the lactic acid accumulating during biosynthesis was neutralised with chalk. The effect caused by the type of phosphorus-containing salt and its mass fraction on the coefficient of whey bioconversion to lactic acid by L. acidophilus AT-I lactic acid bacteria was evaluated along with the rate of formation and yield of calcium lactate. The 2.0 % additive of sodium phosphate disubstituted dodecahydrate was established to provide the highest values for the formation rate and yield of the target product, comprising 0.78 g/(dm(3).h) and 79.96 %, respectively.