Addition of glucose and a commercial enzyme preparation containing glucose oxidase as well as catalase was shown to suppress significantly the growth of Pseudomonas fragi, a common fish spoilage organism, in both nutrient broth and in a fish extract medium inoculated at ambient temperature (260C) (Yoo and Rand, 1995). Dosage of more than 2.0 Enzyme Units/mL of the glucose oxidase preparation with 16 mg/mL glucose in the fish extract medium lowered the pH to approximately pH 4 due to gluconic acid production (Yoo and Rand, 1995). Similarly, the growth of Pseudomonas fluorescens on shrimp kept in a glucose oxidase-glucose solution has been reported to be inhibited (Kantt et al., 1993). In both of the cited studies the glucose oxidase was a commercial preparation containing catalase activity (Kantt et al., 1993; Yoo and Rand, 1995).
In experiments with liquid whole egg, co-addition of 5 Enzyme Units/mL glucose oxidase and 5 mg/mL glucose killed Salmonella enteritidis, Micrococcus luteus, and Bacillus cereus inoculated at 103 cfu/mL after five days of storage of the eggs at 70C (Dobbenie et al., 1995). The addition also exerted a weak bacteriostatic effect on Pseudomonas fluorescens (Dobbenie et al., 1995); in that study the glucose oxidase preparation was also a commercial preparation from A. niger and the preparation was stated to contain a maximum of 1% catalase impurity but a statement of the exact catalase activity content was lacking, however (Dobbenie et al., 1995). If the antibacterial mechanism of glucose oxidase is based on H2O2 production, the observed antibacterial efficiency of the glucose oxidase preparations containing catalase are surprising considering that the catalase removes the H2O2. The available data therefore support the proposition that the lowering of pH achieved from gluconate production may in fact be the main antibacterial principle of the glucose oxidase in these tests. The preservative potential of glucose oxidase has also been tested on poultry products, legs and chicken breasts, but in these products no convincing antibacterial effects of the glucose oxidase treatments were found (Frels et al., 1984; Jeong et al., 1992).
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