Growth-Inhibitory Effect of d -Tryptophan on Vibrio spp. in Shucked and Live Oysters

Abstract

Oysters are the primary transmission vehicles for human Vibrio infections. Raw oyster consumption is frequently associated with gastroenteritis. The current postharvest methods, such as high-pressure processing, used to control Vibrio spp. in fresh oysters are still insufficient because of limited facilities, high cost, and potential adverse effects on production. We demonstrate that adding a small amount of d -tryptophan ( d -Trp) inhibits the growths of Vibrio parahaemolyticus and Vibrio vulnificus in a high-salt environment at even ambient temperature. We further investigated the d -Trp treatment conditions and clarified the relationship between salt and d -Trp concentrations for optimal growth-inhibitory effect of Vibrio spp. The results will be useful for enhancing the effectiveness of d -Trp by increasing salinity levels. Furthermore, in a nutrientfree environment (artificial seawater), a stronger inhibitory effect could be observed at relatively lower salinity levels, indicating that d -Trp may be regarded as effective food preservation in terms of salinity reduction. Therefore, we suggest the use of exogenous d -Trp in a seawater environment as a novel and effective strategy not only for controlling Vibrio in live oysters at even ambient temperature but also for effectively retarding spoilage bacterial growth and extending the shelf life of shucked oysters at refrigeration temperature.