Amino acids analysis during lactic acid fermentation by single strain cultures of lactobacilli and mixed culture starter made from them

Abstract

The interactions among Lactobacillus salivarius, Pediococcus acidilactici and Lactobacillus plantarum in utilizing the amino acids of MRS media were investigated. L. salivarius alone showed relatively good assimilation of various amino acids that existed at only a little amounts in MRS media (Asn, Asp, Cit, Cys, Glu, His, Lys, Orn, Phe, Pro, Tyr, Arg, Ile, Leu, Met, Ser, Thr, Trp and Val), whereas Ala and Gly accumulated in L. salivarius cultures. P. acidilactici, in contrast, hydrolyzed the proteins found in the medium to liberate various amino acids; it utilized Cit, Cys, and Gly for growth, while promoting the accumulation of Ala, Asn, Glu, His, Lys, Orn, Phe, Pro, Tyr, Arg, Ile, Leu, Met, Ser, Thr, Trp, and Val. Similar to L. salivarius, L. plantarum showed relatively good assimilation of various amino acids that existed at only trace amounts in MRS medium (Ala, Asn, Asp, Cit, Cys, Glu, Gly, His, Lys, Phe, Pro, Tyr, Arg, Ile, Leu, Met, Ser, Thr, Trp, and Val). Single-strain cultures of L. salivarius and P. acidilactici exhibited high levels of growth and lactic acid synthesis, whereas single-strain cultures of L. plantarum manifested the lowest cell growth and lactic acid synthesis. The unique individual abilities of the three LAB strains to utilize amino acids for growth and lactic acid production were employed to create a mixed culture that showed enhanced cell growth and lactate production. The results from our mixed culture (L. salivarius and P. acidilactici) experiments suggested that the growth of L. salivarius was stimulated by the amino acids produced by P. acidilactici, enhancing lactic acid production. Mixed cultures were tested at different inoculation proportions (1:1, 2:1, 5:1 and 9:1; given as OD₆₀₀ ratios of L. salivarius: P. acidilactici), and the highest cell growth and lactic acid production values were obtained for the 2:1 ratio.

Keywords:  Amino acids, single and mixed culture, Lactobacillus salivarius, Pediococcus acidilactici, Lactobacillus plantarum

African Journal of Biotechnology, Vol 13(28) 2867-2873