Metagenomic analysis of bacterial community composition in Dhanaan: Ethiopian traditional fermented camel milk

Abstract

This study was conducted to evaluate the safety and bacterial profile of Dhanaan (Ethiopian traditional fermented camel milk). The composition of the microbial community in Dhanaan samples was analysed by a metagenomic approach of 16S rRNA gene amplicon sequencing. Metagenomic profiling identified 87 different bacterial microorganisms (OTUs) in six samples analysed. Although the Dhanaan samples contained various lactic acid bacteria (LAB), they also all contained undesirable microorganisms in large proportions. The following LAB genera were identified: Streptococcus, Lactococcus, and Weissella. One Streptococcus species represented by OTU-1 (operational taxonomic unit) was found in all Dhanaan samples and the dominating species in four out of six samples. This common isolate was found to be closely related to S. lutetiensis and S. infantarius. Undesirable microorganisms from genera such as Escherichia, Klebsiella, Enterobacter, Acinetobacter and Clostridium were, however, also frequent, or even dominant in Dhanaan samples. Thus, this calls for a change in the Dahnaan manufacturing practice to an improved and safer production system. Starter cultures suitable for Dhanaan production might be developed from the Streptococcus, Weissella, and Lactococcus microorganisms identified in this study. However, further safety evaluation and technological characterization need to be conducted on strains defined by OTU-1, OTU-2, OTU-3, OTU-8, and OTU-35 before they can be used as food grade starter cultures.

Bacillus subtilis isolates from camel milk as probiotic candidates

“…Camel milk and its products have been given much attention in the world owing to their beneficial effects such therapeutic and nutritional values 13 , 15 . Recent scientific reports have indicated the camel milk as a rich source for probiotics 19 that aside from nutritional composition as well as the therapeutic and physicochemical properties of milk, information about its microbiota is limited 23 .…”

“…In many countries of dry land and desert ecosystems, camels due to high adaptation to the hostile climatic conditions, have significant role in life of these types of communities by providing meat, milk and transportation 13 . In addition, camels have medical importance through their milk and urine 14 .…”

Camel milk products: innovations, limitations and opportunities

“…Metagenomic profiling of dhanaan samples collected from eastern Ethiopia showed classical and nonclassical species of lactic acid bacteria (LAB) under the genera Lactococcus, Streptococcus and Weissella (Berhe et al 2019). In addition to the LAB, spoilage and/or pathogenic bacteria such as Enterobacter, Klebsiella, Clostridium and Acinetobacter were also observed in the dhanaan samples (Berhe et al 2019). OTU-1 (operational taxonomic unit) was found to be the dominant streptococcus unit in four out of six samples (Berhe et al 2019).…”

Recent Advances in Camel Milk Processing

“…Each camel country has described their traditional fermented milk in terms of microbiological, physicochemical, and chemical properties, as well as volatile organic compound profiles in some cases. The most known fermented camel milk products described in the literature are shubat in Kazakhstan [97] and China [98], khoormog in Mongolia [99], garris in Sudan [100,101], suusac in Kenya [102], laben (lben) in Arabic countries [103], and ititu and dhanaan in Ethiopia [104,105] (Table 2). Other traditional fermented beverages based on a mixture of camel milk and water are available in Mauritania known as zrig [106], in Morocco known as Lfrik [107], and in Iran and Turkmenistan known as chal [108].…”