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Biofilms are significant hazards in the food industry. In this study, we investigated the effects of food additive such as citral, cinnamaldehyde, and tea polyphenols on mixed biofilm formation by foodborne Staphylococcus aureus and Salmonella serotype Enteritidis. The adhesion rates of mixed strains in sub-MIC of additives were determined by a microtiter plate assay and bacterial communication signal autoinducer 2 (AI-2) production via a bioluminescence reporter Vibrio harveyi BB170. The structure of mixed biofilm was analyzed using scanning electron microscopy. The effect of the disinfectants hydrogen peroxide, sodium hypochlorite, and peracetic acid was tested on the mixed biofilm. Our results demonstrated that citral, cinnamaldehyde, and tea polyphenols were able to significantly inhibit mixed biofilm formation, while citral could reduce the synthesis of AI-2. Conversely, we observed a significant increase in AI-2 mediated by cinnamaldehyde. Tea polyphenols at lower concentrations induced AI-2 synthesis; however, AI-2 synthesis was significantly inhibited at higher concentrations (300 m g/ml). Food additives inhibited the adhesion of mixed bacteria on stainless steel chips and increased the sensitivity of the mixed biofilm to disinfectants. In conclusion, citral, cinnamaldehyde, and tea polyphenols had strong inhibitory effects on mixed biofilm formation and also enhanced the effect of disinfectant on mixed biofilm formation. This study provides a scientific basis for the application of natural food additives to control biofilm formation of foodborne bacteria. [ABSTRACT FROM AUTHOR]

Abstract: The Pearl River is the largest river system in south China. The Pearl River estuarine system consists of two parts: the channel network and the estuarine bays. These two parts are connected by rock-bound gorges or ‘men’, which means ‘gate’ in Chinese. During the last transgression, the paleo-bay of the Pearl River estuary was separated into inner- and outer-bays by rocky hills. The water of the bays was linked through a series of rock-bound gorges. These gorges developed into ‘men’ during the delta evolution. Based on in situ hydrographic measurements, analysis of topographic maps and satellite imagery, bore hole records with 14C dating, and application of the long-term morphodynamic model (PRD-LTMM), this paper discusses the morphodynamics of ‘men’ including: (1) the bi-directional jet system associated with ‘men’, (2) the evolution of ‘men’, (3) the convergence of paleo-tidal energy caused by ‘men’, (4) the coupled-development of sub-delta plains and related ‘men’, (5) the effect of ‘men’ on the formation of the channel network. According to this study, the rock-bound outlets of the network system are coincident with the high energy tidal flux during the last 6000years. The locations and formation of the Pearl River outlets and the channel frame were determined by the geographical setting and the dynamic and sediment environment associated with ‘men’. The dynamic structure of the modern Humen and Yamen are typical bi-directional jet systems. There were a series of paleo bi-directional jet systems in paleo Modaomen estuary. The morphodynamic analysis of ‘men’ is a key issue to reveal the evolution of the Pearl River delta and its estuarine system. The evolution of ‘men’ can be summarized into three major stages: bi-directional jet stage, single directional jet stage and post-‘men’ stage. The present ‘men’ in the Pearl River delta are in different stages of evolution. [Copyright &y& Elsevier]