Biofilm formation of Pectobacterium carotovorum subsp. carotovorum on polypropylene surface during multiple cycles of vacuum cooling

During vacuum cooling, polypropylene turnover boxes are repeatedly used for containing vegetables for cooling, while Pectobacterium carotovorum subsp. carotovora (Pcc) can form a biofilm on polypropylene adhesion surface. This study evaluated the effects of multiple cycles of vacuum cooling on the morphology and composition of Pcc biofilm formed on polypropylene turnover boxes. Results showed that Pcc biofilm in different growth stages including adhesion, development and mature phases displayed different responses to vacuum cooling. Pcc biofilm in adhesion stage decreased from 10(6) to 10(5) CFU cm(-2), indicating the positive interference of vacuum cooling on biofilm formation in the initial developmental stage. However, with the increasing of the number of vacuum cooling cycles from 0 to 3, the biomass of Pcc biofilm in the development stage increased from 10(7) to 10(8) CFU cm(-2) and the polysaccharide secretion increased from 7.96 to 16.7 mg cm(-2), showing the promotion of biofilm formation and the secretion of extracellular polymeric substances. Therefore, regular cleansing and sterilisation of turnover boxes are necessary to prevent cross-contamination during vacuum cooling.