Adsorption of plantaricin Q7 on montmorillonite and application in feedback regulation of plantaricin Q7 synthesis by Lactobacillus plantarum Q7

Kieselguhr, bentonite, and montmorillonite were investigated as potential carriers of plantaricin Q7. Highest level of adsorption of plantaricin Q7 was obtained with montmorillonite. Meanwhile, visible inhibition zones were observed against Listeria monocytogenes for montmorillonite adsorbed with plantaricin Q7. Adsorption kinetics showed that the adsorption behaviour followed the pseudo-first-order and Weber's intra-particle diffusion models, suggesting two steps had taken place during the adsorption process. X-ray diffraction assays revealed that plantaricin Q7 was intercalated into the interlayer space of montmorillonites. Electrostatic, hydrogen bonding and hydrophobic interactions proved to play important roles in the mechanisms of interaction between montmorillonite and plantaricin Q7, as shown by infrared spectroscopy analysis. In addition, plantaricin Q7 production was inhibited by feedback regulation with its high concentrations. In order to remove product feedback inhibition in plantaricin Q7 production, a strategy was implemented for its adsorption onto montmorillonite during fermentation. The final plantaricin Q7 output reached 3713.40 IU/mL during fermentation using montmorillonite to adsorb plantaricin Q7, 41.61% higher than that of non- montmorillonite. These results indicate that montmorillonites are suitable carriers for plantaricin Q7 adsorption, and the adsorption of plantaricin Q7 onto montmorillonite during fermentation could be a good method to increase final plantaricin Q7 production.