Lactic acid bacteria isolation from vinal pods (Prosopis ruscifolia) and preliminary characterization for biotechnological purposes

PALOMAR, LUCAS SEBASTIAN; ROMPATO, KARINA; ZARATE, GABRIELA DEL VALLE

Buenos Aires

Congreso; XXIII ANNUAL MEETING OF THE ARGENTINEAN BIOLOGY SOCIETY (SAB); 2021

Sociedad Argentina de Biología

Lactic acid bacteria (BAL) fermentation increases nutritional and organoleptic properties of foods and extends their shelf life. Plant matrices have a native microbiota that can be used to improve biological and functional properties of foods manufactured with them. In this regard, Prosopis ruscifolia is an underused shrub species with nutritional properties that could be improved through fermentation. However, its microbiota and biotechnological potential have not been studied at all. In order to isolate and characterize autochthonous BAL strains from vinal, pods were collected from plants grown in Ibarreta (Formosa). The fresh pods were ground, mixed with sterile water in a 1:1 ratio and incubated under microaerophilic conditions at 37°C for 48 h. Then, the fermented doughs were plated on MRS agar and incubated under the same conditions. Colonies compatible with BAL were isolated, and bacteria were characterized by their morphology, mobility, Gram staining and catalase activity. Acidification capacity and pH reduction were evaluated 24 h after development in a culture medium containing 4% (w/v) pod flour. Amylolytic and proteolytic activities were observed by streaking in MRS agar with 1% (w/v) starch instead of glucose and 1% (w/v) gelatin, followed by the plates staining with Lugol and Coomassie blue, respectively. Significant differences between mean values were determined by Tukey’s test (P < 0.05) using the InfoStat statistical program. The isolated bacteria were non-motile Gram-positive bacilli, without catalase activity. The pH and acidity were significantly lower in the inoculated broths compared to uninoculated controls. No significant differences were observed between the different isolates. Three isolates showed extracellular proteolytic activity, evidenced by the formation of a halo around the colony after staining the agar with a Coomassie blue solution. None of them showed amylolytic activity after being stained with Lugol. Our results represent the first report of the presence of BAL in Prosopis ruscifolia, a species considered an invasive pest, but which could help solve the nutritional problems of the region. More in-depth studies are being carried out on the metabolic activities of the native vinal microbiota in order to evaluate the application of selected microorganisms to the nutritional and functional improvement of vinal and its incorporation into food formulations.