The biodiversity of thermoduric bacteria isolated from whey

Thermoduric gram-positive bacteria are indigenous in milk, cheese, whey and other dairy products. They are capable of surviving heat processes and can result in quality defects and a shortened product shelf life. In Ireland, premium products such as whey protein concentrate (WPC) are often adversely affected by these microorganisms, particularly during the winter months. A high bacterial count in the WPC can result in the product being sold at a lower grade, with an overall loss of revenue for the manufacturer. This study recovered thermoduric bacterial isolates (n=140) from an Irish WPC process during the months of November-February. Using molecular 16S rRNA gene identification, Bacillus licheniformis, Microbacterium lacticum, Staphylococcus warneri, Enterococcus durans and Bacillus subtilis were recorded as the predominant microorganisms in this process line. This is the first known study to report the detection of Microbacterium phyllosphaerae, Neisseria subflava, Rothia aeria and Streptococcus mitis in dairy produce or indeed in any food product. The identification of bacteria at various stages of the WPC production process will support future measures in reducing/removing microorganisms from the process line in question and assist the dairy manufacturer in tackling this costly problem.