Microbiological analysis and assessment of biotechnological potential of lactic acid bacteria isolated from Tunisian flours

This work was carried out to identify lactic acid bacteria (LAB) from baking wheat flours and to evaluate their technological capabilities for potential incorporation in sourdough process. Six samples of wheat flours obtained from different geographical regions of Tunisia were microbiologically analyzed. Several technological features including acidification, antimicrobial, amylolytic, proteolytic, and antioxidant activities of six selected LAB strains were investigated for future in situ applications. Moreover, LAB were investigated for their ability to produce exopolysaccharides. A total of 45 autochthonous LAB were isolated and identified by genetic analysis of 16S–23S rRNA intergenic transcribed spacer (ITS)-generated patterns ITS-PCR. One of each ITS-PCR pattern was subjected to partial 16S rRNA gene sequencing, and strains were identified as Weissella cibaria , Lactobacillus plantarum , Lactobacillus brevis , Pediococcus pentosaceus , Pediococcus pentoseus , Pediococcus acidilactici , Enterococcus faecium , Enterococcus casseliflavus , and Enterococcus faecalis . All tested LAB showed good acidifying ability by decreasing significantly ( p < 0.05 ) the pH of flour extract below 4.0 after 24 h and below 3.0 after 72 h. Pediococcus pentoseus and P. acidilactici presented fermentation quotient (FQ, ratio of lactic and acetic acids) close to the optimal range. All LAB isolates demonstrated extracellular proteolytic activity. Weissella cibaria S25 had the highest radical-scavenging activity with 25.57%. Lactobacillus plantarum S28 demonstrated the highest amylolytic activity (1386 U/mL) followed by P. acidilactici S16 (1086 U/mL). Although, L. plantarum S28 showed the highest production of exopolysaccharides (0.97 g/L). Moreover, varying halo of inhibition was detected against Escherichia coli , Staphylococcus aureus , Aspergillus niger , and Penicillium expansum . This study revealed that autochthonous flour LAB had interesting technological features and thus could be used in sourdough production.