Isolation and identification of lactic acid bacteria present in bean (Phaseolus vulgaris L.) flours

SAEZ, G.; HEBERT, E.M.; SAAVEDRA, L.; PEREZ CHAIA, A.; ZARATE, G.

Simposio; SIBAL 2016. V International Symposium on Lactic Acid Bacteria. Benefitting from Lactic Acid Bacteria. Progress in Health and Food.; 2016

Beans production (Phaseolus vulgaris L.) is one of the most important regional economies in the Northwest of Argentina, mainly in the provinces of Salta and Tucumán. Flours obtained from these legumes possess an interesting nutritional value which turns them into an option for healthy diets. However, these flours should be subjected to industrial processing in order to improve their technological properties and obtain products with higher rheological and organoleptic quality. In this sense, the fermentation with Lactic Acid Bacteria (LAB) is an alternative to enhance flours quality due to the synthesis of metabolites that positively impact in the final product. Therefore, the aim of this work was to isolate and characterize LAB strains from different varieties of P. vulgaris flours to be used in the future for the fermentation of these matrices. Samples of different varieties of beans (Alubia, Pallar, red and black beans)were ground individually, mixed 1:1 with sterile distilled water and incubated aerobically at 37°C for up to 5 days with daily backslopping (10% sourdough + 90% fresh dough). Samples taken at 0, 1, 3 and 5 days were inoculated in selective media for BAL: MRS with cycloheximide 0.1 % and LBS and were also plated in PCA and HyL media to estimate the cultivable microbiota (total aerobic mesophiles and fungi/yeasts, respectively). Evolution of pH was followed during fermentation. Colonies grown in MRS and LBS with presumptive characteristics of LAB (Gram + and catalase -) were selected and differentiated by REP-PCR. The isolates with different profiles were identified by the amplification of the V1 variable region of 16S rRNA. Initial mesophiles counts of 4.13x104, 1.84x104, 4.55x103, and 3.46x104 CFU/g for Alubia, Pallar, red and black varieties, respectively, reached values around 109 CFU/g after 5 days of fermentation for all the doughs, whereas the counts of fungi and yeasts started at 2.22x103, 1.37x103, 5x102 and 3x103 CFU/g for each type of flour, remained around 104 CFU/g during successive days and finally decreased by 1-2 logarithmic orders at the end of fermentations. Lactic microbiota began to dominate after 24 h of fermentations with values of 2.57x108 in Alubia, 6.78x107 in Pallar, 1.20x107 in red and 2.26x108 CFU/g in black beans, and reached final values of 6.74x108, 5.35x108, 1.71x108 and 2.65x108 CFU/g, respectively. The pH of all doughs decreased from 6.6-6.2 to 4.3-3.9 at the end of fermentations. LAB strains were identified as Enterococcus caseliflavus (2), E. durans (4), E. faecium (5) E. mundtii (1), Lactobacillus rhamnosus (1), Lactococcus garvieae (3), Weissella cibaria (4), and W. paramesenteroides (5). These results represent the first step in the selection of suitable starters for legume flours fermentation.