Inhibition of Antimicrobial Prodigiosin Production in Serratia marcescens Using Cyclodextrin-Immobilized Microgel Beads Prepared by a Non-Contact Jet Dispensing System

Some gram-negative bacteria possess N-acylhomoserine lactone (AHL)-mediated quorum sensing (QS) as one of the cell-to-cell communication systems for regulation of various cell functions. Increase in the AHL concentration above its threshold leads to simultaneous activation of target gene expression in each cell. The AHL can diffuse in and out of the cells through the cell membrane. Artificial reduction of the AHL concentration can inhibit the AHL complex formation with its receptor inside the cell. In this study, the AHL that diffused out into the culture broth was captured on α-cyclodextrin (CD), which possesses a hydrophobic cavity and a hydrophilic shell. The α-CD-immobilized calcium alginate gel beads, which were prepared using a non-contact jet dispenser, were immersed in the culture medium during the cell growth of Serratia marcescens AS-1, which was used as the model opportunistic human pathogen. The trapping of AHLs on immobilized α-CDs due to hydrophobic interaction of the AHL acyl-chain led to an effective inhibition of AHL-mediated prodigiosin production to approximately 2% in the presence of 27 wt% gel beads in the culture broth. The results of our study suggest that CD has high potential to regulate QS involved in matter production, biofilm formation, and virulence factor expression.