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The aim of this study was to isolate lactic acid bacteria from two varieties of grape bunch cultivated in Tunisia (cardinal and red-globe) in order to assess their ability to inhibit the growth of their most widespread contaminant, Aspergillus niger aggregats and Aspergillus carbonarius. Antifungal activity of 18 isolates was investigated using overlay technique; selected isolates were than identified using 16s rDNA sequence analysis. Isolates with antifungal activities were screened out and studied for their probiotic properties using in vitro tests (tolerance to simulated gastric jus, bile salts, hydrophobicity properties).The most efficient strain was also investigated for its ability to reduce the concentration of ochratoxin A (OTA) on liquid medium. Determination of OTA content in media was released using HPLC analysis. Selected strains (RG7B) (C11C) and (RG8A) showing a good antifungal activities against Aspergillus niger aggregats and Aspergillus carbonarius were identified as Pediococcus pentosaceus and Lactobacillus plantarum, respectively. Pediococcus pentosaceus (RG7B) showed promising potential probiotic characteristics and had a high ability for OTA removal after 48 h of incubation in both MRS and PBS media. The OTA removal percentage was significantly higher in MRS than in PBS media (84 and 25%, respectively). This study provides evidence for the control of black Aspergillus growth in grape and OTA detoxifying by the use of autochthones LAB strains having antifungal effect and probiotic potential.

Date Palm sap is a fresh juice called “Legmi” widely produced and consumed in Southern Tunisia. The aim of this research was to study microbiological group’s distribution present in 10 palm sap samples, and to select Lactic acid bacteria (LAB) with suitable properties for use as starter cultures in sap lactic fermentation. Microbiological analysis showed high load in fresh palm sap. Mesophilic aerobic bacteria varied from 6.07 to 8.57 log cfu/ml, coliforms ranged from 3 to 6.78 log cfu/ml, yeasts between 3 and 8.47 log cfu/ml and LAB from 5.36 to 8.47 log cfu/ml. Ten strains were chosen randomly to study the acidifying activity when growing in palm sap. These strains, tentatively identified by API 50CHL, were divided into two groups: Leuconostoc mesenteroides subsp. mesenteroides and Lactobacillus delbrueckiisubsp. delbruckii. All the strains were considered as fast acidifier since ∆pH was higher after 6 h of fermentation. The higher acidifying strains KH3 (L. delbrueckii) and 5B4 (L. mesenteroides), were used to inoculate sap in pure culture. During the fermentation, pH decreased from 6.94 and 6.36 for 5B4 and KH3, respectively, to about 4.0±0.1 after 24 h of fermentation for both strains. Total titrable acidity increase from 0.2 and 0.4% for 5B4 and KH3 respectively to around 3.0%. The application of these strains as starter cultures in the production of fermented palm sap could be investigated on further studies. Key words: Date palm sap, legmi, lactic acid bacteria, starter culture.