Abstract:
The brewing yeast demand of Ethiopian brewery industries entirely relies on foreign sources, which is expensive and hinders profitability and global competency. Indeed, the need for diversified brewery products in global brewing sectors led to the finding of alternative strains to produce beer with distinctive flavor, which might have local figures and impact the global beer market. Fermented foods and beverages are important sources of alternative brewing yeasts. Thus, this study was purposed to isolate, screen, and identify yeasts from Ethiopian fermented beverages (tella, tej, korefe, areki tenses, terahi, bubegne, shamita, borde and cheka) for brewery industry application. Moreover, this study attempted to investigate the safety, brewing performance, and probiotic potential of the identified yeast isolates. A progressive screening and subsequent selection approach was followed to select and identify isolates that best-met potential brewing characteristics. Best-performing isolates were identified using the internal transcribed spacer (ITS) regions as a barcode. Following, identified isolates were screened for brewing safety concerns and extra-beneficial roles using culture-plating methods. These were further screened, and selected isolates were evaluated for laboratory scale brewing performances following standard European Brewery Convention (EBC) protocols. Fourier-Transformed-Infrared spectrum matching was used to qualitatively determine the chemical profile of the produced beers. Brewing candidate strains were evaluated for potential probiotic traits in an in vitro condition. A total of 113 isolates were isolated, of which 44 isolates were low- H2S-producers. These were screened for glucose fermentation, and all isolates fermented glucose and formed gas ranging from 3.7 to 5 mL after 48 hrs of incubation at 30 oC. The pattern of sugar utilization showed that all preselected isolates fermented and assimilated glucose sucrose, maltose, fructose, galactose and mannose, but not lactose, mannitol, arabinose, xylose and starch. The subsequent screening of them for glucose fermentation, growth and survival under different physiological settings revealed that, they fermented glucose and grew to different degrees in all tested pH values, temperature and osmo-stressing glucose concentrations. But only nineteen isolates comparably fermented glucose, grew and survived at 10% (v/v) ethanol and 0.1mM hydrogen peroxide (H2O2) concentration. These isolates have produced ethanol ranging from 1.53 to 2.1 alchol by volume percentage (ABV%), comparable with the commercial strain, from 2% (w/v) glucose. They also demonstrated viability and vitality ranging from
XVIII
89.0±6.7 to 96.3±2.7% and 1.90±0.12 to 2.31±0.02 acidification power (
