LAUSR

Abstract Today, there is an increasing trend to supplement food with phenolic compounds due to the beneficial effect on health. Lactic acid bacteria (LAB) have been shown to form protective biofilms in food industry. However, surrounding condition, such as additives play a significant role in biofilm formation. The aim of this study was to investigate the influence of honey phenolic extract (HPE) on biofilm formation (BF) of Pediococcus pentosaceus and Lactobacillus fermentum. To this end, optimal BF was tested under different environmental conditions, such as pH and cultivation time. Micro-titer plate assay was performed to assess biofilm-forming abilities. In addition, FT-IR spectroscopy and scanning electron microscopy (SEM) were used to monitor the changes in bacterial membrane composition and biofilm morphology. It was observed that the addition of HPE at 0.094 mg/mL reduced BF of L. fermentum and P. pentosaceus by 28% and 15%, respectively. However, BF of P. pentosaceus remained constant as the concentration of phenolic compounds increased. Micrographs of P. pentosaceus revealed a dense production of extracellular polymeric substances that contributed to the bacterial tolerance against phenolic compounds. Band shifts corresponding to COC ring vibrations, confirmed that exopolysaccharides constitute part of P. pentosaceus biofilm. On the other hand, higher concentrations of HPE were found to disrupt biofilm formation by L. fermentum, resulting in loosely associated clusters.