In vitro testing of biocides synergy with a new biofilm model with endogenous biofilm-forming bacteria strain obtained from a papermaking environment

Bacteria in papermaking environment can be divided in two main phenotypes; planktonic bacteria and biofilm bacteria. Biofilm bacteria in general are more resistant to biocides than free swimming i.e. planktonic bacteria. Due to the slow growth rate of biofilm a new model was developed where the EPS structured backbone of biofilm was replaced with natural hydrogel. The biofilm model was tested using both endogenous bacterial strains and a laboratory strain (DSM type strain). Oxidative and organic biocides were tested, also in combination for the screening of synergetic effects on both bacteria within the EPS backbone, and planktonic bacteria. Results implied strong synergy for combinations of oxidative and organic biocides. In addition, results confirmed that laboratory strains of the same bacterial species were not as resistant to the biocides as the endogenous strain obtained from the papermaking environment. Also, the bacteria in the synthetic biofilm resisted the effect of biocides.