ABSTRACT
In recent years, research on yeasts as probiotics has gained more and more interest, which will allow the development of "new" products in the probiotics market. In this context, seventeen yeast strains isolated from Rabilé, a traditional beer produced in Burkina Faso, were assessed for their probiotic attributes. The yeast identification was performed by molecular methods, including PCR-RFLP and 5.8S-ITS region sequencing. Saccharomyces cerevisiae (14 strains) was the predominantly identified species, followed by Pichia kudriavzevii (2 strains) and Rhodotorula mucilaginosa (1 strain). Except for R. mucilaginosa, all yeast strains grew well at human temperature. The yeast strains showed high resistance when they were exposed to simulated gastrointestinal conditions. Auto-aggregation ability was between 70.20 ± 10.53% and 91.82 ± 1.96%, while co-aggregation with E. coli ranged from 24.92 ± 3.96% to 80.68 ± 9.53% and with S. enterica serovar Typhimurium from 40.89 ± 8.18% to 74.06 ± 7.94%. Furthermore, the hydrophobicity of isolated strains toward n-hexane was in the range from 43.17 ± 5.07% to 70.73 ± 2.42%. All yeast strains displayed high antioxidant capabilities, and the strains did not show hemolysis halos, such that they can be considered safe. Additionally, S. cerevisiae strains strongly inhibited the growth of foodborne pathogens. This is the first preliminary study to identify and characterize the yeast strains isolated from Rabilé with interesting probiotic properties.
ABSTRACT
BACKGROUND: Soumbala is a highly loved alkaline traditional fermented food condiment in Burkina Faso. It harbors various microbiota dominated by fermentative Bacillus spp. as functional microorganism with little confirmed health-promoting properties. METHODS: The present study aimed to evaluate six Bacillus strains previously isolated and identified from soumbala. These strains were selected as presumptively safe bacteria for probiotic and technological characteristics. These strains were assessed for in vitro probiotic criteria (tolerance to acidic pH, gastric juice, 0.3% (m/v) bile salts, intestinal juice and 0.4% (w/v) phenol, cell surface hydrophobicity, auto-aggregation capacity, antimicrobial activity against foodborne pathogens, antibiotic susceptibility and biofilm production) and technological properties, including protease, amylase, lipase, and tannase activity, as well as poly-γ-glutamic acid (PGA) production and thermo-tolerance. RESULTS: All tested Bacillus strains (B54, F20, F24, F21, F26 and F44) presented variable relevant probiotic properties (good tolerance to pH 2 and pH 4, gastric juice, bile salts, intestinal juice and phenol), with marked differences in hydrophobicity and auto-aggregation capacity ranging from 73.62-94.71% and 49.35-92.30%, respectively. They exhibited a broad spectrum of activity against foodborne pathogens depending on target pathogen, with the highest activity exhibited by strain F20 (29.52 mm) against B. cereus 39 (p < 0.001). They also showed good biofilm production as well as variable hydrolytic enzyme activities, including protease (43.00-60.67 mm), amylase (22.59-49.55 mm), lipase (20.02-24.57 mm), and tannase (0-10.67 mm). All tested Bacillus strains tolerated temperature up to 50 °C, while only strains F26 and F44 showed the best PGA production. CONCLUSION: Overall, the tested cultures exhibiting potential probiotic and technological characteristics; particularly B. cereus F20, B. benzoevorans F21, B. cabrialessi F26, and B. tequilensis F44 could be a source of probiotic-starters of commercial interest in the production of high-quality soumbala.
