Development of Bioactive Solid Support for Immobilized Lactococcus lactis Biofilms in Bioreactors for the Production of Nisin

It is essential to increase microbial population during the fermentation processes. Polypropylene was modified through reactive blending for it to have anhydride groups able to covalently bind with the polycation chitosan and for it to harbor Lactococcus lactis biofilms to produce the antimicrobial peptide nisin. Biofilm development was conducted for 5 cycles of fermentation in rich and minimal media. After 5 batch cycles of fermentation for biofilm growth in rich media, the chitosan-modified polypropylene contained 6.4 ± 0.4 log(CFU/cm²), whereas the polypropylene support without chitosan contained 5.9 ± 0.4 log(CFU/cm²). Infrared spectroscopy and electron and atomic force microscopy analyses confirmed higher nutrient and biomass deposition on the chitosan-modified polypropylene. After 24 h of fermentation in rich media, the L. lactis biofilms grown over the chitosan-modified polypropylene support produced a maximum nisin concentration of 523.5 ± 256.7 IU/mL, while cells in suspension produced 240.6 ± 5.1 IU/mL at the same period. L. lactis biofilms grown in minimal media over the chitosan-modified polypropylene support produced a maximum nisin concentration after 24 h of incubation in rich medium of 8.5 ± 3.9 IU/mL. Through reactive blending, it is possible to prepare supports that can harbor biofilms able to significantly increase the production of metabolites during fermentations.