HEBERT Elvira Maria
congresos y reuniones científicas
Molecular characterization of lactic microbiota in Andean fermented potatoes (Tocosh)
Simposio; IV International Symposium on Lactic Acid Bacteria: Food, Health and Applications.; 2013
Tocosh is a fermented potato-based food which is traditionally produced in the Central Andean region of Perú. This product, usually the main staple food for local population, is produced byplacing different potato varieties (aprox. 500 Kg) on a straw bed in a hole practiced near a water spring. Potato fermentation was accomplished during a variable period of time (up to 8 months) and modifications in potato composition are produced by effect of bacteria, fungi and yeast. During these processes, potatoes were removed and used in different food preparations which are claimed to exert probiotic and antibiotic effects. Samples were collected at 0 (fresh potatoes, M1),3 (M2) and 8 (M3) month holes for lactic acid bacteria (LAB) isolation and identification. Results showed total viable counts in PCA medium in the range of 107 CFU/g for M1 and M2 samples, while counts of 2 x 105 CFU/g were found for M3 potato sample. LAB loads counted in MRS, MRS-starch (MRS-S), MRS-maltose (MRS-M) and Yeast Glucose Lactose Peptone (YGLP) agar media exhibited values independent of the medium used, which were in the range of 1.1 to 1.6 x 104 CFU/g for M1, 1.7 to2.5 x 109/g for M2 and 1.1 to 5.7 x 108 CFU/g for M3 sample. pH values varied from 5.5 in fresh potatoes to 3.8 in 3-month fermented potatoes, reaching a final pH of 4.2 at 8-month fermentation time. From a total of 84 isolated colonies, those presenting Gram (+) and catalase (-) phenotype (54 colonies) were selected; 55% of them presented bacilli morphology while 45% were cocci. Chromosomal DNA was extracted and analysed by RAPD to assess the microbial diversity among LAB isolates. A considerable polymorphism among isolated strains was observed, 39 different RAPD profiles were detected when M13 and XD9 primers were applied. The taxonomic identities were achieved by means of 16S rRNA gene sequencing. Results showed that fresh potatoes contained Leuconostoc mesenteroides (39%); M2 sample Leuc. mesenteroides (78%) and isolates belonging to the Lactobacillus genera (12%), in which L. sakei was included. After 8 months, L. sakei and L. fermentum species were identified. In tocosh, the enrichment in lactobacilli during fermentation would support the beneficial effects attributed to this traditional fermented product. Investigation of these indigenous foods may provide information on unknown microbial genetic resources which can be exploited as new functional starter cultures to improve nutritional and functional quality of traditional Andean foods.