Impact of disinfectant and nutrient concentration on growth and biofilm formation for a Pseudomonas strain and the mixed cultures from a fine papermachine system

Biofilm formation in papermaking processes could inflict financial loss by interrupting paper machine operation and pose a potential health hazard. A mixed microbial culture obtained from paper machine slime and a Pseudomonas strain (identified as Pseudomonas putida HB45) which is tolerant to the alkyl dimethyl benzyl ammonium chloride (quaternary ammonium chloride, QAC) were used to investigate the interplay between disinfectants and glucose on bacterial growth and biofilm formation. QAC and 2,2-dibromo-3-nitrilopropionamide (DBNPA) were found to be effective at concentration lower than isothiazolone in both standardized Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) tests. Crystal violet staining technique demonstrated that biofilm formation of P. putida HB45 and the mixed culture could be controlled by modest dosage of DBNPA and QAC; however, they could be barely eliminated due to high MBC to MIC ratios. In simulated papermaking processing water, glucose was shown to increase the average biofilm formation rates during stationary phase for both P. putida HB45 and the mixed culture under the presence of biocides. Complexity and population diversity of biofilm of the paper machine slime was observed by in-situ cryo-scanning electron microscopy. Confocal laser scanning microscopy (CSLM) was employed to show qualitative and partial quantitative biofilm formation under various circumstances. The results of this study could assist improving strategy for controlling biofilm formation in papermaking processes.