Before collecting the sample, some information about the production of Rabilé has been collected with the sellers and the producers. An article on the quality of Rabilé used as condiment in Burkina Faso has been published in African Journal of Biotechnology.

The ferment of local beer “Rabilé” was collected from 70 (seventy) sellers of local beer in 7 (seven) localities Ouahigouya, Fada N’Gourma, Réo, Bobo Dioulasso, Grarango, Tougan Dissin (Figure 1) representing different ethnic regions of Burkina Faso. From each producer, one hundred grams (100 g) of ‘‘Rabilé’’ was sampled and maintained at 4˚C in isothermal box for laboratory analysis.

Enumeration of total aerobic mesophilic flora and yeasts

Each sample of Rabilé was properly mixed to ensure homogenization of the microorganisms present in the fermented product. Triplicate samples of Rabilé (10 g) were introduced aseptically into 90 ml (1:10 dilution) of buffered Peptone water (0.85% (wv-1) Biomerieux, France) into stomacher blister and stored at ambient temperature for 30 min. The mixture introduced in a McCartney bottle was mixed with a vortex (Gemmy Industrial Corporation, Italy) for 5 min. Decimal dilutions were plated and 0.1 ml of each of dilution was pipetted in duplicate into appropriately marked Petri dishes. Total count of total aerobic mesophilic flora was determined on plate count agar (PCA) after 24 h incubation at 30˚C and yeasts was determined on Sabouraud Dextrose Agar containing chloramphenicol (50 µ∙ml⁻¹) after 3 to 5 days of incubation at 30˚C, under aerobic condition. Fifty (50) yeast strains were isolated and subjected to morphological, cultural, biochemical, fermentation and assimilation tests.

Isolated colonies with distinct morphological appearance were picked up aseptically and subjected to several tests for identification. The classical methods used by [13] based on examination of morphological, biochemical, cultural and physiological properties of yeasts isolated in pure cultures were applied using Wickerham medium. Preliminary confirmation was based on microscopic observation. The isolates were tested for the fermentation of sucrose, lactose, glucose

and raffinose, as well as the assimilation of selected nitrogen sources: nitrate, ethylamine, L-lysine, cadaverine and sulfate of ammonium. The assimilation of carbon sources was performed using API 20 C AUX strips (BioMérieux, Lyon, France) according to the manufacturer’s instructions. The diazonium blue B reaction, a test to differentiate between ascomycetous and basidiomycetous yeasts, was performed as described by [14] .

For the analytical data, mean values, as well as standard deviation, are reported. The data were analyzed using the statistical program, XLSAT 2014.5.03. The on-line available software (http://http:www.cbs.knaw.nl) of Centraal bureauvoor Schimmel cultures (Central Bureau of Fungal Cultures), Utrecht, the Netherlands was used for identification of yeasts.

Table 1 shows an enumeration of flora aerobic mesophilic total (FAMT) and yeasts found in Rabilé collected from different sampling sites. The results were converted to log₁₀ CFU∙g⁻¹. The average values of FAMT ranged between 8.42 ± 0.34 and 10.07 ± 0.18, while the amount of yeasts ranged between 7.24 ± 0.26 and 8.28 ± 0.20.

The results of FAMT and yeasts enumeration from Rabilé (Table 1) shows that FAMT and yeasts counted in Rabilé were higher than FAMT and yeast counted in a sorghum beer burukutu (7.95 ± 0.45 and 7.49 ± 0.54) as reported by [15] . Djêgui [6] thought that the difference between yeasts counted in kpete-kpete, tchoukoutou ferment and in burukutu could be due to the fact that there is a significant difference between the dry matters of both products. The results of Table 1 show there is a significant difference between FAMT and yeasts counted from the localities. However, the number of FAMT and yeasts

*Values with the same letter in the same column are not significantly different (P < 0.05), FAMT: Flora Aerobic Mesophilic Total, cfu: Colony Forming Unity.

counted from Rabilé is similar to the other authors found in alcoholic beverages fermented. Indeed, Djegui [1] and Keita [3] found 9.24 and 10.35 log₁₀ CFU∙g⁻¹ of yeasts respectively in Kpete-Kpete of Benin and Rabilé of Burkina Faso. Also, Atter [15] counted 8.41 ± 0.38 log₁₀ (UFC∙g⁻¹) after the wort fermentation. The higher rate of FAMT could be due by contamination by other microorganisms. Mogmenga [2] showed that Rabilé used as condiment by certain communities of Burkina Faso is contaminated by Staphylococcus aureus and total coliform. The utilization of Rabilé as condiment could be a food contamination source.

Table 2 presents the morphological, cultural and biochemical characteristics of yeasts strains isolated from Rabilé. According to these characteristics, yeasts strains have been gathered into three groups. The group that presented a main difference with other groups was a group III. The color of those strains was red, and in broth medium there is not sail formation. The difference between members of group I and group II was the number of ascospores, there were 8 ascospores in the strains of group I and 4 ascospores in the strains of group II. All of strains of these groups were catalase⁺ and oxidase⁺.

Considering carbon (API 20C AUX gallery) source assimilation profile (Table 3), fourteen (14) different groups of yeasts were distinguished. The majority of yeasts strains assimilated glucose (100%), galactose (74%), saccharose (66%) and maltose (100%). Others assimilated L-arabinose, D-Xylose, D-sorbitol, Methyl-α D-Glucopyranoside, D-raffinose and D-trehalose. However, none of them assimilated Calcium 2-keto-Gluconate, Inositol, N-acetyl-glucosamine and D-cellobiose.

Group I: Oy3-3; Kb3-4; Oy3-10; Bf1-1; Tk3-8; Tk3-8; Ga3.10; Kb2.9, Og3.2, Og2.3, Dr1.6, Ga2.1; Fd2.10, Bf2.7, Bf2.2, BB1.7, BB1-1, Dr1-6, Tk3-10, Oy1-7, Fd3-9, Bf3.4, Bf2.6, Oy3.3, Oy3.10, Tk3.7, Kb3.4, Bf1.1, Bf2.5, Oy2.5, Bf1.8, Bf2.3, Ga3.7, Ga2-3, Fd3-3, Tk2-1; Group II: Fd2-2, Oy3-8, Oy1-5, Tk2-6, Oy2-9; Ga2-5; Dr1-9; Ga3-3; BB1-6; Tk3-9; Group III: Tk2-9, BB1-9, BB3-3, BB3-1; (+) Presence and positive reaction; (−) Absence and negative formation.

A: Tk2-9, BB1-9, BB3-3, BB3-1; B: Fd2-2, Og3-4, Ga3-4, Bf1-9, Dd2-8, Tk3-8, Oy3-8, Ga3-7, Tk2-6; C: Oy3-8, BB1-6, Tk3-7; D: Oy2-9, Ga2-5, Dr1-9, BB2-1, Ga2-3; E: Ga3-10, Og3-2, Ga3-3, Kb3-3, F: Bf2-7; G: Kb2-9, Og2-3; H: Dr1-6, Ga2-1; I: Oy3-9; J: Fd2-10, Oy3-10, Ga2-5, Dr1-9, Oy1-5; K: Bf2-2, Oy2-5, Bf1-8, Bf2-3; L: BB1-7, Bf3-4, Oy3-3, BB1-1, Dr1-6; M: Oy3-3, Bf2-6; N: Og2-9, Bf2-5, Bf1-1; (+) Assimilated; (−) Not assimilated.

The results in Table 4 show that the majority of yeasts strains isolated from Rabilé fermented glucose, maltose, sucrose, galactose and raffinose whereas none fermented lactose. The nitrogenous sources assimilation test show that a majority of yeasts strains isolated from Rabilé assimilated L-lysine, cadaverine and sulfate of ammonium, whereas a minority assimilated nitrate. The diazonium blue B test revealed that 8% of the isolates were basidiomycetous whereas 92% were ascomycetous. According to their fermentation profile and the nitrogen assimilation pattern, the fifty yeasts strains could be grouped into 18 distinct groups. 18% were in the first group, 14% were in the second group, 10% in the third group and the rest are distributed in the other 11 groups.

According to the phenotypic characteristics the fifty yeasts strains isolated were found to belong to four genera and seven species of yeasts. These are Saccharomyces cerevisiae (64%), Rhodotorula muciloginosa, (8%), Candida pseudorhangii (6%), Candida heliconiae (12%), Candida utilis (4%), Shizosaccharomyces pombe (4%) and Sporobolomyces odoratus (2%). Saccharomyces cerevisiae was found to be the dominant yeast species in the Rabilé.

Glu: Glucose; Suc: Sucrose; Lac: Lactose; Gal: Galactose; Mal: Maltose, Raf: Raffinose, Nit: Nitrate; Lys: Lysine; Eth: Ethylamine; Cad: Cadaverine; SAM: Sulfate of Ammonium; ²DBB = Biazonium Blue B; (+) Fermented or assimilated; (−) Did not fermented or did not assimilated.

The diversity of yeasts strains contained in Rabilé can be explained by the fact African traditional alcoholic beverage production results from spontaneous fermentation and as a result, both desirable and non-desirable strains are present in the product [16] . Saccharomyces cerevisiae appeared in this study to be the most predominant yeast strain in Rabilé (64%) (Figure 2), a traditional fermented beer starter using as condiment in Burkina Faso. These findings are in accordance with previous studies reported by other authors. Konlani [8] found that Saccharomyces cerevisiae accounted for 55% - 90% of yeast population in samples of sorghum beer originated from Togo and Burkina Faso. N’guessan [17] found that Saccharomyces cerevisiae is the most representative yeast strain (87.36%) associated with tchapalo fermentation in Ivory Coast. Similarly, [15] in Ghana found that the majority of 180 yeasts strains isolated from burukutu were Saccharomyces cerevisiae. Also, Djegui [1] and Djêgui [6] found a higher frequency of Saccharomyces cerevisiae respectively at 54% and 71% from otché and kpete-kpete, traditional starters of Benin opaque sorghum beer. According to [18] to be accepted as Saccharomyces cerevisiae, the yeast strain should be able to assimilate glucose, sucrose, maltose, raffinose and ethanol. But in this study, some of the isolates classified as Saccharomyces cerevisiae could not assimilate all of these sugars. Similar results were found by [1] [6] [19] with yeasts

strains identified as Saccharomyces cerevisiae but that could not assimilate all of those sugars. The identification of yeasts from Rabilé shows that the consumption of Rabilé could cause food intoxication. If Saccharomyces cerevisiae and Candida utilis have been approved for use as additive by Food and Drug Administration [20] , it is not the case for Rhodotorula muciloginosa, Candida pseudorhangii, Candida heliconiae, Shizosaccharomyces pombe and Sporobolomyces odoratus even if they are used to produce value-added products.