A psychrotrophicBurkholderia cepaciastrain isolated from refrigerated raw milk showing proteolytic activity and adhesion to stainless steel

Abstract

The proteolytic activity of a psychrotrophic strain of Burkholderia cepacia isolated from refrigerated raw milk was characterized. Bur. cepacia produced proteolytic activity during growth at refrigeration temperature, with maximum activity at pH 6-7. The enzyme showed relative thermal stability in the range 40-50°C during 25 min, and maintained 80% its initial activity at 76°C/30 s. Milk coagulation assay showed that the crude protease from Bur. cepacia caused coagulation from day 2 for skimmed milk, whereas coagulation was observed from day 5 for whole milk. The adherence of this strain to stainless steel was evaluated, and the substrata had around 107 CFU/cm2 after 15 to 60 min incubation. Results on biofilm development suggest that this bacterium could adhere and to form biofilms even at refrigeration temperatures. These results indicate that Bur. cepacia may represent a potential hazardous to milk and dairy products.

Proteolysis in ultra‐heat‐treated skim milk after exposure to multispecies biofilms under conditions modelling a milk tanker

“…Bacteria found in raw milk are able to form biofilms and produce enzymes at various temperatures (Nörnberg et al . ; Cleto et al . ; Teh et al .…”

Diversidade e controle de biofilme formado pela microbiota do leite cru

“…The dominant genera observed during the days of the three treatments belonged to two classes, Gammaproteobacteria and Bacilli, with the class Gammaproteobacteria being dominant in almost every day, with an approximate average of 85% of the relative abundance (Figure 5A). The contaminating microbiota of refrigerated raw milk includes both Gram-positive and Gram-negative microorganisms, but the latter represents more than 75%, among which a large part belong to the Gammaproteobacteria class (Nörnberg et al 2011;Pinto et al 2015). observed that in the biofilms formed by the microbiota of raw milk at 7 ºC, Gammaproteobacteria and Bacilli represented about 50% each of the microorganisms identified.…”