The influence of PU foams modification on the efficiency of Citrobacter freundii cells immobilization

The purpose of the study was to modify PU (polyurethane) foams to increase the efficiency of Citrobacter freundii cells adhesion. The immobilization can contribute to better productivity during the bioconversion of glycerol to 1,3-propanediol (1,3-PD). The results of the study showed that C. freundii immobilized on foams with organic additives could decompose more glycerol and produce more 1,3-PD than cells immobilized on pure foams. The immobilization made production in long-term operations or repeated runs possible. The results of the experiments have also proved that the foams with additives, especially with wood chips and peanut shells, would be the most suitable carriers because they allow the immobilization of a higher number of bacterial cells. It was demonstrated that the initial number of C. freundii cells in all samples (before incubation) was 1.2×106 CFU/mL. The results showed that the accumulation of bacterial cells in the control sample with pure PUF (polyurethane foams) was 1.5×107 CFU/mL after 24 hours of incubation (the number of bacterial cells attached to surface of foams). It was determined that the accumulation of bacterial cells in samples with 15% of additives at 30 °C increased to 2.17×107/ 3.37×107/ 1.25×108/ 1.65×108/ 5.65×107 CFU (PUFbtb, PUFab, PUFwch, PUFps, PUFrc) CFU/mL after 24 hours of incubation.