Exploring the lactic microbiota present in Guava fruits. Molecular identification of lactic acid bacteria

RUIZ RODRIGUEZ, L.; BLECKWEDEL, J.; RAYA, R.R.; HEBERT, E.M.; MOZZI, F.

Simposio; IV International Symposium on Lactic Acid Bacteria: Food, Health and Applications.; 2013

Lactic acid bacteria (LAB) are naturally present in different niches such as vegetables, fermented dairy products, sausages, cereals, gastrointestinal and urogenital tracts, etc. Because of their beneficial properties certain LAB are used as starter cultures in the manufacture of fermented foods and beverages, as probiotics and in the production of specific compounds (e.g. nutraceutics). Research on the microbial diversity of specific niches has been pursued to better understand the dynamics of complex (fermented) food ecosystems and to find interesting metabolite-producing strains. Exploring the LAB diversity in virgin niches may lead to the isolation of unique strains or species, many still unknown, with interesting properties. To date very few studies on the isolation of LAB from fresh and fermented fruits have been reported. A wide variety of exotic indigenous fruits exists in the Northern region of Argentina many of them not yet commercialized. Guava (Psidium guajava), a fruit tree belonging to the Myrtaceae family, is native from Tropical America and currently distributed in tropical and subtropical areas worldwide. Different guava fruit varieties exist, which can have round or oval shape and white, yellow or pink pulp. The aim of this work was to explore and identify the LAB microbiota present in pink (G1) and yellow (G2) guava fruits. Guavas were aseptically collected and processed using a stomacher. LAB isolation was performed by culture-dependent techniques using different growth media (MRS for LAB, and FYP1 and FYP30 for fructophilic LAB). Fifty seven Gram positive, catalase negative isolates were submitted to RAPD-PCR fingerprinting technique using M13b and XD9 primers. Molecular identification of representative isolates of each RAPD-PCR obtained fingerprints was performed by partial sequencing of the 16S rDNA. Analyses of the lactic microbiota of guava fruits showed that in the G1 variety Weissella minor (9 strains), Leuconostoc mesenteroides subsp. mesenteroides (2 strains) and Leuconostoc pseudomesenteroides (15 strains) were present while Leuconostoc pseudomesenteroides (2 strains), Lactobacillus brevis (6 strains) and Lactobacillus plantarum (1 strain) were identified in the G2 variety. From the total twenty two fructophilic LAB strains were isolated. The obtained results showed that the presence of certain LAB species was dependent on the guava variety. This is the first study to report on the isolation of LAB species from guava fruits belonging to the Northwestern region of Argentina. Further studies are needed to evaluate the potential health beneficial properties or industrially relevant characteristics of the isolates.