Optimal Conditions for Expression of Enzymatic Activities in Bacillus Strains Essential for Production of Soumbara, a Functional Fermented Food Involved in Blood Pressure Homeostasis

Abstract

Background: Soumbara is a traditional fermented food involved in the blood pressure homeostasis. The functional properties of this food strongly depend on the fermentative microbiota. In this study, we screened and identified at molecular level, some potential starters strain among the main microbiota associated with soumbara in Cote d’Ivoire, and investigated the conditions for optimal expression of their functional performance. Methods: We screened and identified by ribosomal gene sequencing, interesting microbial strains and conditions for optimal expression of their functional performance notably proteolytic, lipolytic, pectinolytic, amylolytic and cellulolytic activities was investigated using semi quantitative method. Results: The isolated microbiota was composed of 90.41 % of Bacillus strains, the rest being yeast and lactic acid bacteria. A total of 4 performant strains, specifically Bacillus subtilis (BS14P), Bacillus subtilis (KS16P), Bacillus velezensis (HS27M) and Bacillus pumilis (PS10P) were extracellular enzymes producing strains with halo diameter ranging between 1.9 and 2.8 cm. These strains grew optimally in the temperature range of 30- 35°C at pH 7-8. The largest enzyme producer Bacillus velezensis strain (HS27M) was remarkably able to grow well at relatively high temperature (40°C) and in a larger pH range (6-9). Proteolysis enzymes were produced optimally at 40-45°C, pH 7 whereas lipolysis occurred maximally at 40°C, pH 7. Likewise maximum pectinolytis, cellulolysis and amylolysis occurred at 45°C, pH range 7-8. Conclusion: This study suggests Bacillus velezensis HS27M as valuable starter cultures for the production of soumbara with bioactive and organoleptic quality.