Preliminary performance of heterofermentative lactobacilli in non-dairy matrixes: silage and dough

BRAIDA, JÉSICA; PEVERENGO MARÍA ROCÍO; PUJATO SILVINA ALICIA; QUIBERONI ANDREA; CAPRA MARÍA LUJÁN

San Miguel de Tucumán

Simposio; Simposio; V International Symposium on Lactic Acid Bacteria. Benefitting from lactic acid bacteria. Progress in health and food; 2016; 2016

CERELA

Obligated heterofermentative lactobacilli (OHeL) produce CO2 from hexoses and may be present in raw milk as non-starter lactic acid bacteria (NSLAB). As all lactic acid bacteria possess GRAS status (Generally Recognized As Safe). Their presence in silage and in sourdough has also been reported. The aims of this study were to characterized 16 dairy autochthonous OHeL strains (12 Lactobacillus fermentum, 2 Lactobacillus brevis, 1 Lactobacillus buchneri and 1 Weissella cibaria) and assess their performance in non-dairy matrixes. Inoculum (2%, v/v) and optimal temperature, Topt (37ºC, L.fermentum and 30ºC, the rest of the species) were determined by microplates assays. In spite of their isolation from dairy samples, all strains displayed scarce growth in milk. The acidification activities (potentiometric titration NaOH N/9 pH 8.4) were low and proteolytic activities (OPA test) almost null, when strains were developed at their Topt (24 h, reconstituted sterile milk 10% w/v with or without extract of yeast 0.25% w/v). The growth on liquid corn extract medium of L. brevis and L. buchneri was evaluated by cell counts, pH determination and organic acid quantification (lactic and acetic acids, HPLC, 72 h). The strains were able to grow reaching the highest increments (0.9-1.2 log10 orders) between 24 and 72 h. The pH values descended up to 4.4-5.0 in the cultures and the concentration of lactic (0.89±0.01 - 1.18±0.09 mg/mL) and acetic acid (0.24±0.02 me - 0.31±0.01 mg/mL) was showed promissory for use in silage. All (16) strains were tested for exopolysaccharides (EPS) production. EPS can improve texture and prolong shelf life of bread. Screening was made by visual detection of mucoid colonies grown in agar media (MRS and MRS maltose-sucrose 1-10% w/v MRS-MS; 2-4 d, 30ºC). L.fermentum (strains 22 and 68), con L. brevis (strains 61 and 66), W cibaria (strain 20) y L. buchneri (strain 39) were selected and the better results were found in MRS-MS. Growth of W. cibaria 20 in wheat flour and in a celiac commercial mix was assessed (cell counts, total titratable acidity and pH determination). In both controls (without W. cibaria), the spoilage bacterial counts (initially 10^3 -10^4 UFC/g) was notably increased (4.7-4.9 log10 orders) after 24 h of incubation (30 ºC). On the contrary, this spoilage flora was completely inhibited when W. cibaria 20 was inoculated (5xl0^7 UFC/g). The strain was able of growing in both kinds of dough and showed cell count increases (0.7-0.9 log10 orders) after 24 h. The strain produced more acidity and higher descent on pH values in comparison with its respective controls without inoculums. The abilitv to grow on corn extract medium as well as in both types of dough, sets the studied strains as interesting candidates to be starter cultures for fermentations in non-dairy matrixes.