Evaluation of diversity of Candida species isolated from fermented cassava during traditional small scale gari production in Nigeria

Abstract

The yeast population dynamics during cassava fermentation at different time regimes was determined and the Candida species isolated from the fermented mash were identified using combined phenotypic and genomic methods. The yeast population increases as the fermentation progresses with corresponding pH reduction mediated by lactic acid bacteria and yeast co-metabolism. The phenotypic characteristic of the Candida species isolated from fermented cassava during gari production in Nigeria was determined using the sugar fermentation profile of the API 20AUX that generated the phenotypic identity of Candida species as Candida guilliermondii, Candida krusei, Candida maris, Candida galabrata. Only strain 1RB identified phenotypically as C. guilliermondii fermented all the sugars except inositol and lactose. Although, the strain 2RB identified by the API 20AUX as C. maris fermented galactose, all other strains could only ferment glucose with the presence of pseudohypae. The result of the comparison of the 18S rDNA gene sequencing with the blast database identified the strains of C. guilliermondii 100% C. krusei 98%, Candida inconspicua 100%, Candida rugopelliculosa 98%. The results also demonstrated that different strains of Candida species participated in the traditional fermentation of cassava and differentiated C. krusei from C. inconspicua using the 18S rDNA gene sequencing. C. inconspicua has not been previously reported due to its phenotypic relatedness to C. krusei. C. inconspicua may not be a good candidate to be selected as starter culture due to its medical importance; it must be genetically differentiated from the diverse strains of C. krusei that participated in the fermentation.