Microbial community dynamic in tomato fruit during spontaneous fermentation and biotechnological characterization of indigenous lactic acid bacteria

Abstract

The present work aimed to study the microbial dynamics in tomato fruits under spontaneous fermentation process and the biotechnological properties of lactic acid bacteria (LAB) for future starter culture formulation. The isolation of native microbial species was performed using diverse specific media. Microbial identification was performed using the variability analysis and sequencing of ribosomal DNA-amplified fragments. Moreover, LAB (n = 85) were evaluated for several physiological and technological characteristics, including salinity and temperature tolerance, esculin and arginine hydrolysis, carbohydrate fermentation, exopolysaccharide production, and antagonistic activity. As well, lycopene, flavonoid, and antioxidant compounds were determined in fermented tomato samples. Bacterial isolates were assigned to ten bacterial genera, namely, Microbacterium, Bacillus, Staphylococcus, Pantoea, Flavobacterium, Enterobacter, and Citrobacter including three genera of LAB: Lactobacillus, Leuconostoc, and Enterococcus. Moreover, the amplification of ITS1-5.8S-ITS2 regions allowed the detection of Aspergillus fumigatus and three species of yeast: Candida carpophila, Meyerozyma caribbica, and Wickerhamomyces onychis. During the spontaneous fermentation, the majority of spoilage bacteria and fungi completely disappeared after the third week, whereas LAB and yeast remain until the end of fermentation. LAB exhibited important technological features and high antibacterial activity against human and food-borne pathogenic bacteria. Furthermore, LAB produced various antioxidants for fermented food products. Promising results of this study allowed the identification of the major encountered taxa during spontaneous fermentation of tomato and underline the importance of LAB as a starter culture to achieve microbiologically safe products providing prolonged stability and flavor of vegetable-derived foods.