INFLUENCE OF GLUCOSE OXIDASE ON THE GROWTH OF ESCHERICHIA COLI 0157:H7, LISTERIA MONOCYTOGENES, AND SALMONELLA TYPHIMURIUM IN UNIVERSAL PREENRICHMENT BROTH

摘要

Glucose oxidase (GO), a food‐grade enzyme, was compared with OxyraseTMoxygen reducing membrane fraction in Universal Preenrichment Broth (UPB) for enhancement of the growth of the facultatively anaerobic pathogens Escherichia coli O157:H7, Salmonella typhimurium, and Listeria monocytogenes Scott A. Oxidation‐reduction potential (ORP) and pH changes in UPB following the addition of GO (4 units/ml) or OxyraseTM(0.5 units/ml) were measured. Microbial growth was evaluated at 0, 3, 6, 18, and 24 h of incubation using spiral plating. Nonenzyme supplemented UPB served as the control. OxyraseTMprovided a higher oxygen scavenging action in terms of ORP decrease during the initial 6 h of incubation. However, no difference occurred in Eh between OxyraseTMand GO by 18 h, with both enzyme systems effectively reducing the Eh compared to that of the control. A 1.0 pH unit reduction was observed in GO‐supplemented UPB after 18 h, indicating production of gluconic acid. The pH decrease in OxyraseTM‐ supplemented media was 0.2 units. By 6 h, the E. coli O157:H7 population was enhanced by 0.6 and 1.4 log CFU/ml in OxyraseTM‐supplemented media, compared to the control and GO‐supplemented media, respectively. By 18 h, 0.4 and 0.9 log CFU/ml growth enhancements of the E. coli O157:H7 populations were seen in GO‐ and OxyraseTM‐supplemented media, respectively, compared to the control. By the end of 18 h, counts of S. typhimurium and L. monocytogenes increased by 0.6 and 0.2 log units, respectively, in GO‐supplemented media compar