Identification of deteriorating activity and the apr gene in the microbiota isolated from raw milk in Caxias, MA

Abstract

Among milk contaminating bacteria, psychrotrophic ones stand out as the main responsible for deterioration, because they can multiply in refrigeration temperatures. The apr gene carries the information to produce alkaline metalloprotease, a heat-resistant enzyme capable of degrading milk proteins. The objective of this work was to investigate, by biomolecular methods, the presence of the apr gene and the deteriorating potential of proteolytic bacteria isolated from raw milk in a Maranhão state microregion. A total of 112 raw milk samples were collected from February to June 2018, in dairy farms of São João do Sóter and Caxias, MA. Microbiological analyzes were performed at the Federal Institute of Maranhão (IFMA), Campus Caxias, and the biomolecular assays at the Laboratory of Inspection of Animal Products (LIPOA) in the State University of Londrina (UEL). Tests were performed to classify proteolysis, lipolysis and acidifier potential at the optimal temperature (36 °C/2 days) and psychrotrophic activity (7 °C/10 days). 10 (9%) positive isolates for the apr gene were found, all belonging to the genus Pseudomonas, corroborating other researches in the state that point to the great deteriorating potential of bacteria found in this locality. Thus, as in other regions of Brazil, refrigerated raw milk produced in the state of Maranhão needs to be obtained hygienically avoiding contamination with spoilage microorganisms that may compromise the integrity and quality of fluid milk and derivatives intended for trade.