Isolation and identification of lactic acid bacteria from lentils (Lens culinaris) and pea (Pisum sativum) flours

SAEZ, GD; PÉREZ CHAIA, A; SAAVEDRA L; HEBERT, EM; ZÁRATE G

San Miguel de Tucumán

Congreso; XII Congreso Argentino de Microbiología General; 2017

Asociación Civil de Microbiología General (SAMIGE)

Lentils (Lens culinaris) and peas (Pisum sativum) are the most consumed varieties of legumes in Argentina. These pulses and their derived products are considered of great nutritional value due to their high protein and dietary fiber contents. However, flours obtained by mill of these seeds have to be subjected to additional industrial processing in order to improve their technological properties that allow obtaining products with higher rheological and organoleptic quality. In this regard, fermentation with lactic acid bacteria (LAB) represents an attractive option for food industry since these microorganisms are able to remove antinutritional factors and release several metabolites that positively impact in the product. Therefore, the aim of this work was to isolate LAB strains from flours of lentils and peas and characterize them technologically in order to select the most appropriate for fermentation of these food matrices. Four samples of lentils and one sample of peas obtained from local markets were ground individually, mixed 1:1 with sterile distilled water and incubated aerobically at 37°C for up to 5 days with daily backslopping for the enrichment of the endogenous microbiota. Samples taken at 0, 1, 3 and 5 days were spread on selective agar for LAB (MRS with cycloheximide 0.1 % and LBS), and also plated in PCA and HyL media to estimate total aerobic mesophiles and fungi/yeasts respectively. Evolution of pH was followed during fermentation. Colonies grown in MRS and LBS that were Gram positive and catalase negative were differentiated by REP-PCR. The isolates with different profiles were identified by sequencing the gene encoding for 16S ribosomal RNA. Initial average counts of 2.07x104 and 7.8x103 CFU/g for lentils and peas, respectively, reached values near to 108-109 CFU/g after 24 hours of fermentation at the fifth backslopping cycle, whereas counts of fungi and yeasts started at 8.25x102 and 5x101 CFU/g for each type of flour, remained at 104 CFU/g during successive days of backslopping and decreased by 1-2 logarithmic orders at the end of the fermentation cycles. Lactic microbiota began to dominate after the first backslopping cycle with values of 1.05x107 CFU/g in lentils flour and 4.4x105 CFU/g in peas, reaching final values of 4.11x108 and 6.4x109 CFU/g respectively. Regarding pH, it decreased in all doughs from 6.4-6.0 to 4.5-3.8 at the end of fermentations. LAB isolates were identified as Enterococcus durans (1 strain), E. faecium (2), Lactobacillus plantarum (1), Lactococcus garvieae (2), Weissella cibaria (5), and W. paramesenteroides (7). Further studies on technological properties of these strains for selection of the most appropriate to be applied to development of a legume based functional food are at present ongoing.