Thermo-resistant enzyme-producing bacteria isolated from the internal surfaces of raw milk tankers

In this study, bacteria were isolated from the internal surfaces of raw milk road tankers by swabbing the surfaces during two seasons, winter and summer. Bacteria producing thermo-resistant enzymes were selected for further characterization and their ability to form biofilms in vitro. Of the 153 isolates able to produce enzymes, 52 produced thermo-resistant enzymes. The number of bacteria recovered from stainless steel chips during a biofilm screening assay after 24 h of exposure ranged from 2.7 to 7.6 log cfu cm−2. Twelve of these bacteria, identified by 16S rDNA sequence analysis, belonged to the genera Bacillus, Staphylococcus, Streptococcus, Pseudomonas or Serratia. In addition, some of these isolates were able to grow at low temperatures (7 °C). This study shows that bacteria present on the internal surfaces of raw milk tankers may be a previously unreported source of thermo-resistant enzymes in raw milk.