Microbial Biofilms in the Food Industry—A Comprehensive Review

Biofilms, present as microorganisms and surviving on surfaces, can increase food cross-contamination, leading to changes in the food industry’s cleaning and disinfection dynamics. Biofilm is an association of microorganisms that is irreversibly linked with a surface, contained in an extracellular polymeric substance matrix, which poses a formidable challenge for food industries. To avoid biofilms from forming, and to eliminate them from reversible attachment and irreversible stages, where attached microorganisms improve surface adhesion, a strong disinfectant is required to eliminate bacterial attachments. This review paper tackles biofilm problems from all perspectives, including biofilm-forming pathogens in the food industry, disinfectant resistance of biofilm, and identification methods. As biofilms are largely responsible for food spoilage and outbreaks, they are also considered responsible for damage to food processing equipment. Hence the need to gain good knowledge about all of the factors favouring their development or growth, such as the attachment surface, food matrix components, environmental conditions, the bacterial cells involved, and electrostatic charging of surfaces. Overall, this review study shows the real threat of biofilms in the food industry due to the resistance of disinfectants and the mechanisms developed for their survival, including the intercellular signalling system, the cyclic nucleotide second messenger, and biofilm-associated proteins.

Biofilm-control strategies based on enzymic disruption of the extracellular polymeric substance matrix – a modelling study

A kinetic model is proposed to assess the feasibility of strategies for the removal of biofilms by using substances that induce detachment by affecting the cohesiveness of the matrix of extracellular polymeric substances (EPSs). The model uses a two-state description of the EPS (natural EPS and compromised EPS) to provide a unified representation of diverse mechanisms of action of detachment-promoting agents (DPAs), which include enzymes that degrade the EPS and other agents described in the literature. A biofilm-cohesiveness factor describes local increases in detachment rates resultant from losses in cohesive strength. The kinetic model was implemented in an individual-based biofilm-modelling framework, including detachment rates dependent on local cohesiveness. The efficacy of treatments with DPAs was assessed by three-dimensional model simulations. Changes in treatment efficacy were evaluated quantitatively by using a Thiele modulus, which quantifies the relationship between diffusion of the DPA through the biofilm matrix and DPA decay rate, and a Damköhler number relating the rate of EPS reaction with a DPA and the rate of EPS production by the micro-organisms in the biofilm. This study demonstrates the feasibility and limits of implementing biofilm-control strategies based on attacking the EPS.