Inhibition of Salmonella Enteritidis adhesion and biofilm formation by β-glucosidase B from Microbacterium sp. BG28

Abstract

SalmonellaEnteritidis is the most commonly reported pathogen for foodborne illness outbreaks in both underdeveloped and developed regions. S. Enteritidis biofilms, which form on various food contact surfaces, are resistant to conventional physical and chemical cleaning and disinfection procedures routinely used in food processing. The aim of this study was to identify novel, industrially applicable enzymes that are active against S. Enteritidis biofilms. We describe the properties and anti-biofilm activity of heterologously expressed β-glucosidase B derived from the environmental strain Microbacterium sp. BG28 (BglB-BG28) collected from gills of bream fish. The enzyme inhibited adhesion and the early stages of biofilm formation in clinical isolates of S. Enteritidis. At a concentration of 200 μg/mL, BglB-BG28 effectively reduced biofilm formation, by decreasing biofilm biomass by 50% and metabolic activity within biofilms by 80%. The enzyme reduced the formation of air-liquid biofilms on various surfaces, including plastic, glass and metal, as observed by fluorescence microscopy. BglB-BG28 inhibited biofilm formation in Escherichia coli, another important food pathogen that also forms cellulose-rich biofilms. Using o-NPG as substrate, the enzyme showed activity at temperatures up to 50 °C and in a pH range between 4 and 8, high tolerance to sodium chloride and glucose, and compatibility with nonionic detergents. Importantly, no toxicity was observed in the model system Caenorhabditis elegans even at an enzyme concentration of 1 mg/mL. These results suggest that the β-glucosidase BglB-BG28 is a promising candidate for the development of a new enzyme-based disinfection protocol that can be used in food processing facilities.