42-3

M. RASCH¹, T. B. Rasmussen², T. O. Larsen², M. Givskov², and L. Gram¹. (1) Dept. of Seafood Research, Danish Institute for Fisheries Research, c/o Technical Univ. of Denmark, Building 221, DK-2800 Kgs. Lyngby, Denmark, (2) BioCentrum, Technical Univ. of Denmark, DK-2800 Kgs. Lyngby, Denmark

Many Gram-negative bacteria use acylated homoserine lactones (AHLs) to regulate expression of phenotypes in relation to cell density, the so-called quorum sensing (QS). QS is involved in expression of virulence and spoilage in a number of Gram-negative bacteria. AHLs have been detected in several types of spoiling food products. Bacterial spoilage of bean sprouts is characterized by soft rot and the most important bacteria are pectinolytic Erwinia carotovora and Pseudomonas fluorescens. QS is employed to regulate spoilage phenotypes such as protease, pectinase, cellulase, and siderophore production in a bean sprout spoiling Pectobacterium. Also, clotting of milk by Pectobacterium is regulated by QS. Consequently, compounds that block QS (quorum sensing inhibitors (QSI)) without affecting growth of the bacteria might become instrumental in novel food preservation strategies. Halogenated furanones from the red alga Delisea pulchra share structural similarities with AHLs and inhibit a number of QS systems. Chemical reactivity and instability as well as toxicity of some compounds stresses the need for new QSI compounds. We have evaluated the effect of a synthetic analogue of the D. pulchra furanones, furanone C-30, and a series of new QSIs on the expression of spoilage in two food model systems where spoilage is controlled by bacterial QS: bean sprouts and milk. Some of the QSIs, which were used in concentrations where bacterial growth was not inhibited, reduced protease, pectinase and siderophore production of the bean sprout spoilage Pectobacterium. In three of five experiments, bean sprouts inoculated with the food spoilage Pectobacterium and treated with C-30 spoiled later and to a lesser extent than non-treated sprouts. Treatment with several different new QSIs delayed the clotting spoilage of milk. Results from these experiments as well as the perspectives of using QSIs to delay food spoilage will be discussed.

Session 42, Control of quorum sensing signals and antimicrobial effects on foods
2:30 PM - 5:30 PM, Monday PM Room 296

2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana