Interactions between lactic and propionic acid bacteria

Abstract

In some cheeses, propionic acid bacteria (PAB) ferment lactate to propionate, acetate and CO2 which are important in determining the flavour and texture of the cheese. Interactions between 14 strains of lactic acid bacteria (LAB) (Lactobacillus helveticus, Lb acidophilus, Lb lactis, Streptococcus thermophilus and Lactococcus lactis) and 4 strains of PAB (Propionibacterium freudenreichii and Pacidipropionici) were studied in whey. Stimulation or inhibition was judged by the effect on growth rate and final cell mass (OD600). No inhibition of growth was found. The growth of all 4 strains of PAB was stimulated by Lb helveticus and Str thermophilus. The degree of stimulation of the PAB by the other LAB varied. In control and Lb helveticus RR whey, L lactate was used preferentially over D lactate by P freudenreichii KM. Lb helveticus RR increased the levels of amino acids and peptides in the whey. All of the amino acids, except threonine and cysteine, and some of the peptides were used during subsequent growth of P freudenreichii KM. The addition of aspartate stimulated growth of P freudenreichii KM in control whey and reduced the amount of lactate converted to propionate, but not acetate. The stimulant(s) was stable to heating to 121 °C for 15 min and eluted in several peaks after chromatography on Sephadex G-25. Ultrafiltration resulted in a total loss of activity. © 1995 Elsevier/NRA.