The Effects of Chemical and Mechanical Stresses on Bacillus cereus and Pseudomonas fluorescens Single- and Dual-Species Biofilm Removal

Inês B Gomes,Manuel Simões,Madalena Lemos,Anabela Borges,Susana Fernandes,Lúcia C Simões

doi:10.3390/microorganisms9061174

Inês B Gomes, Manuel Simões + Show 4 more

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https://doi.org/10.3390/microorganisms9061174

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Journal: Microorganisms	Publication Date: May 29, 2021
Citations: 10	License type: CC BY 4.0

Affiliation: University of Porto, University of Minho

Abstract

Biofilm control is mainly based on chemical disinfection, without a clear understanding of the role of the biocides and process conditions on biofilm removal. This study aims to understand the effects of a biocide (benzyldimethyldodecyl ammonium chloride—BDMDAC) and mechanical treatment (an increase of shear stress -) on single- and dual-species biofilms formed by Bacillus cereus and Pseudomonas fluorescens on high-density polyethene (HDPE). BDMDAC effects were initially assessed on bacterial physicochemical properties and initial adhesion ability. Then, mature biofilms were formed on a rotating cylinder reactor (RCR) for 7 days to assess the effects of chemical and mechanical treatments, and the combination of both on biofilm removal. The results demonstrated that the initial adhesion does not predict the formation of mature biofilms. It was observed that the dual-species biofilms were the most susceptible to BDMDAC exposure. The exposure to increasing emphasised the mechanical stability of biofilms, as lower values of (1.66 Pa) caused high biofilm erosion and higher values (17.7 Pa) seem to compress the remaining biofilm. In general, the combination of BDMDAC and the mechanical treatment was synergic in increasing biofilm removal. However, these were insufficient to cause total biofilm removal (100%; an average standard deviation of 11% for the method accuracy should be considered) from HDPE.

Highlights

The purpose of this study was to understand the effects of the quaternary ammonium compound (QAC) and benzyldimethyldodecyl ammonium chloride (BDMDAC) on the control of single- and dual-species biofilms of Bacillus cereus and Pseudomonas fluorescens, two bacteria typically encountered in biofilms found in the food industry [7,21,22,23]
The thermodynamic approach was applied to assess the interaction between bacteria and high-density polyethene (HDPE), allowing the prediction of the initial adhesion process
The RCR proved to be a versatile tool to investigate the efficacy of a combined strategy of chemical and mechanical treatment of single- and dual-species biofilms of B. cereus and

Summary

Introduction

Food-processing facilities have strict cleaning and disinfection standards to control spoilage and pathogenic microorganisms that can cause outbreaks of diseases and constitute a risk for public health. This concern has a special focus when microorganisms adhere to a surface and form biofilms [1]. Current disinfection practices used in industrial settings apply clean-in-place (CIP) protocols. Acidic detergents are often applied to clean high food debris and mineral deposits. The use of disinfectants and detergents is, sometimes, intercalated by rinses with water turbulence or scrubbing, to induce biofilm removal [5,6,7]. The low susceptibility and high viscoelastic properties of biofilms hinder their control [8]

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