Technological characterisation and probiotic traits of yeasts isolated from Sha'a, a Cameroonian maize-based traditional fermented beverage

Abstract

The current trend in starter selection is to combine both technological and probiotic properties to standardise and make functional artisanal fermented beverages such as Sha'a whose properties are very variable due to the lack of a known starter. The objective of this work was to study technological and probiotic properties of yeasts isolated from Sha'a sold in Bamenda, Bafoussam, Bonabérie, Dschang, Foumbot, Mbouda and Njombé (Cameroon). The isolated yeasts were studied for their ability to produce CO2 from glucose, to grow in the presence of 8% ethanol, 20% glucose and pH 3, to assimilate maltose and to produce ethanol. Then, the survival of the pre-selected isolates was assessed in simulated gastric (pH 2 and 3) and intestinal juices, followed by self-aggregation, co-aggregation, hydrophobicity, haemolysin, gelatinase, biogenic amine production, antibiotic and antifungal susceptibility, bile salt hydrolase and antiradical activity. The selected isolates were identified by sequencing the 5.8S/28S rRNA gene. From the 98 isolates obtained, 66 produced CO2 from glucose and 16 were then selected for their ability to grow in the presence of 8% ethanol, 20% glucose, pH 3 and maltose. The overall survival of isolates ranged from 4.12 ± 1.63 to 104.25 ± 0.19% (LT16) and from 0.56 ± 0.20 to 96.74 ± 1.60% (LT66) at pH 3 and pH 2 respectively. All of them have remarkable surface hydrophobicity properties. Based on principal component analysis, 5 isolates were selected as the best. However, only 3 of them, LT16 (the most promising), LT25 identified as Saccharomyces cerevisiae and LT80 as Nakaseomyces delphensis, do not produce a virulence factor. The latter can deconjugate bile salts with a maximum percentage of 60.54 ± 0.12% (LT16) and the highest inhibition of DPPH° radicals was 55.94 ± 1.14% (LT25). In summary, the yeast flora of Sha'a contains yeasts capable of fermenting and producing ethanol while producing bioactive compounds that would benefit the consumer.