Microbial interactions associated with indigenous fermented milk

English: Fermented foods contain essential nutrients needed to maintain optimum health as well as other components that help in the delaying and prevention of diseases such as chronic illnesses. Indigenous naturally fermented milk of different regions in Africa play an important role in their daily diet and it helps rural woman to generate a household income. The literature review focused on the microbial composition of fermented milk in different regions in Africa (Botswana, Lesotho, Namibia and Swaziland). Furthermore, the positive and negative interactions associated with fermented milk were discussed in detail. Fermented milk is the result of the activity of a group of microorganisms. Each of these organisms plays an important role in the production of the final fermented product. Before fermentation, undesired microorganisms were present in the samples, but after a four day fermentation the yeasts and lactic acid bacteria (LAB) interactions created an environment impossible for pathogens to survive. The yeasts provide essential growth compounds for the starter culture (LAB) but remained at low numbers at the end of fermentation because of being outcompeted by faster growing LAB. The dominant LAB of the different regions was determined by DGGE and culture sequencing. Enterococci and Lactoccoci were found to be the dominant LAB followed by Leuconostocs and Streptococci. Enterococcus durans species comprised 32% of the isolated LAB. The microbial composition has beneficial effects not only for the consumer but may assist in the improvement of the final product. The microbial interaction between dominant LAB and yeasts frequently observed in dairy products was also monitored during a study in Lesotho. During the growth studies the LAB in combination with the yeasts had a much better growth rate, but in contrast the yeasts grew better on its own compared to those in combination with LAB. For the change in chemical composition it was also found that if in co-culture more organic acids were produced resulting in a rapid decrease in pH levels. During fermentation a small number of LAB proofed to have antagonistic effects against a series of pathogenic bacteria and were further evaluated by evaluating the fermentation process of milk of Lesotho and the LAB's inhibition effect. Salmonella anterica, Shigella sonnei, Staphylococcus aureus and Escherichia coli were completely inhibited by Lactobacillus plantarum and Enterococcus mundtii/feacium. Further studies need to be done in the isolation of novel lactic acid bacteria to provide insight on the preservation and safety of fermented milk products.