Caractérisation de certaines souches microbiennes évoluant dans le blé fermenté et mise en évidence de leurs activités enzymatiques.

Abstract

In Algeria, the wheat was fermented in the MATMOUR (underground silo); this technique starts to disappear because of settlement of the farming populations in the urban areas. Today, fermentation is carried out in metal or plastic barrels. During the process of fermentation, the wheat is subjected by the action of the micro-organisms and/or the enzymes, with desirable biochemical changes. In this context, our study targeted two fermented wheat samples, in barrels with or without vinegar, during 15 month. The purpose of it is to evaluate the biochemical composition, to demonstrate the microbial flora and their extracellular enzymes such as amylases, proteases and lipases. The comparative study of the biochemical composition, between the results of our samples and those of a wheat not fermented (according to the references), made it possible to distinguish from the significant modifications especially on the level of the lipids and the starch within the fermented wheat samples. The starch constitutes the substrate more degraded during the process of fermentation. The microbiological analysis enabled us to isolate, 07 isolates of moulds, 3 isolates of yeast and 40 isolates of lactic acid bacteria. The study of the properties of the isolates supported their ranking among nine kinds: Penicillium (6 isolates), Mucor (1 isolate), Saccharomyces (1 isolate), Candida (1 isolate), Pichia (1 isolate), Pediococcus (6 isolates), Streptococcus (8 isolates), Lactococcus (13 isolates) and Lactobacillus (13 isolates). The description of their enzymatic activities showed that the majority of the isolates of the fungus flora (moulds and yeasts) are amylolytic (moulds: 5 isolates; yeasts: 1 isolate), proteolytic (moulds: 4 isolates; yeasts: 1 isolate) and lipolytic (moulds: 5 isolates; yeasts: 1 isolate). At the 40 isolates of the lactic flora, the raised enzymatic activities are amylolytic (12 isolates) and proteolytic (27 isolates).