Polyphasic characterization of lactic acid bacteria isolated from Beninese sorghum beer starter

Abstract

Tchoukoutou is a Beninese traditional sorghum beer obtained by mixed fermentation including yeast and lactic acid bacteria (LAB). The starter's LAB communities as well as their biotechnological importance remain unknown. Furthermore, the sprouted grain of Sorghum bicolor, which is used during the beer processing, contains a cyanogenic glucoside (dhurrin). In order to elucidate Beninese sorghum beer starter LAB microbiota, 69 LAB isolated from traditional starters were characterized using a polyphasic approach including phenotypical characterization (physiology and MALDI-TOF MS) and 16S rRNA gene comparison. Based on the enzymes substrate specificity, LAB expressing aryl-β-d-glucosidase and amylase were indexed as potential candidates for dhurrin removal and saccharification improvement. All isolated bacteria belong to the same genus Lactobacillus with different strains of the five species L. fermentum, L. plantarum, L. helveticus, L. paracasei and L. brevis and diverse metabolic pathways. MALDI-TOF MS is a good method for accurate and high-throughput LAB identification. Several facultative hetero-fermentative LAB such as L. plantarum and L. paracasei express β-d-glucosidase and amylase. These β-d-glucosidase producers LAB will likely cleave the conjugated glucose of dhurrin, thereby contributing to detoxification if used for controlled sorghum mash bio-acidification.