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

Abstract

Aims: 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. Methods and Results: 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 3Æ49 and 4Æ25. The predominant lactic acid bacteria (LAB) in nyarmie were Leuconostoc mesenteroides 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. Conclusions: The flora in products from different producers varied in the LAB composition present and may result in variations in product quality. Significance and Impact of the Study: Development and use of starter cultures for nyarmie may be beneficial in improving the consistency of product quality