Characterization of dominant microbiota of a Ghanaian fermented milk product, nyarmie, by culture- and nonculture-based methods

To characterize the predominant micro-organisms in a Ghanaian traditional fermented dairy product, nyarmie, made from cows' milk, using both culture- and nonculture-based methods. Samples of nyarmie were analysed from three production sites in Accra, by determining the counts on selective culture media. The microbial diversity occurring in nyarmie was also evaluated by 16S/18S ribosomal DNA PCR amplification and denaturing gradient gel electrophoresis. Results showed that nyarmie contained lactococci and lactobacilli in the range of 10⁸ and 10¹⁰ CFU ml⁻¹, respectively, and yeasts at around 10⁷ CFU ml⁻¹. The pH ranged between 3·49 and 4·25. The predominant lactic acid bacteria (LAB) in nyarmie were Leuconostocmesenteroides ssp. mesenteroides, Streptococcus thermophilus, Lactobacillus delbrueckii ssp. bulgaricus, Lact.helveticus, Lact. delbrueckii ssp. lactis and Lactococcus lactis, while Saccharomyces cerevisiae was the predominant yeast species. Lactobacillus delbrueckii ssp. delbrueckii was not detected by cultivation but its predominance was revealed by PCR-DGGE analysis. The flora in products from different producers varied in the LAB composition present and may result in variations in product quality. Development and use of starter cultures for nyarmie may be beneficial in improving the consistency of product quality.