Advances in the treatment of problematic industrial biofilms

Abstract

In nature, microorganisms tend to form biofilms that consist of extracellular polymeric substances with embedded sessile cells. Biofilms, especially mixed-culture synergistic biofilm consortia, are notoriously difficult to treat. They employ various defense mechanisms against attacks from antimicrobial agents. Problematic industrial biofilms cause biofouling as well as biocorrosion, also known as microbiologically influenced corrosion. Biocides are often used to treat biofilms together with scrubbing or pigging. Unfortunately, chemical treatments suppress vulnerable microbial species while allowing resistant species to take over. Repeated treatment cycles are typically needed in biofilm mitigation. This leads to biocide dosage escalation, causing environmental problems, higher costs and sometimes operational problems such as scale formation. New treatment methods are being developed such as enhanced biocide treatment and bacteriophage treatment. Special materials such as antibacterial stainless steels are also being created to combat biofilms. This review discussed some of the advances made in the fight against problematic industrial biofilms.

Protein Activity Sensing in Bacteria in Regulating Metabolism and Motility

“…This requires multiple modes of signal integration and regulatory crosstalk, which might involve the direct and indirect sensing of environment-or host-derived compounds and metabolites (Sule et al, 2017;Lopes and Sourjik, 2018) as well as metabolic protein activities which feed into sensing. In addition to taxis receptors which perform regulatory functions, some organisms might also dedicate entire chemotaxis systems to perform exclusively regulatory functions benefiting specific lifestyles such as bacterial biofilms or host-associated biology (García-Fontana et al, 2013;Xu et al, 2017). For instance, in the enteropathogen V. cholerae, there are three different operons (cluster I, II, and II) encoding for chemotactic-related genes (Ringgaard et al, 2018).…”

Microbiologically-Influenced Corrosion of 1020 Carbon Steel in Artificial Seawater Using Garlic Oil as Natural Biocide

“…Most of the time microorganisms are in the sessile state, thus composing biofilms 5 . Sessile cells, which are attached to the steel surface, are directly responsible for MIC because they can utilize extracellular electrons or secrete highly concentrated corrosive metabolites underneath the biofilms 4,6 . Thus, as the control of problematic biofilms is necessary to mitigate MIC, the generally used methods include cleaning procedures, application of organic coatings, cathodic protection and chemical treatments with biocides 7 .…”

“…Chloride, glutaraldehyde and quaternary ammonium compounds are the biocides most widely used in the control of biocorrosion [9][10][11] . However, sessile cells are very difficult to mitigate because of their diffusional barrier (which slows down the penetration of biocides), intentionally low metabolic rate (which reduces the biocide intake), preservation of persistent cells, upregulation of resistance genes that code for proteins that degrade antimicrobials and presence of efflux pumps to remove harmful chemicals 6,12 . Therefore, due to the various defense mechanisms employed by biofilms, high dosages of biocides must be used in field applications to eliminate the sessile cells.…”

“…Therefore, due to the various defense mechanisms employed by biofilms, high dosages of biocides must be used in field applications to eliminate the sessile cells. Moreover, the repeated treatment cycles usually needed to avoid the formation of new biofilms on the metallic surfaces may create resistant microorganisms 6,13 .…”

“…The toxicity and residual concentration of the mostused commercial biocides in industrial effluents are of high environmental concern 14 , increasing the process cost and, sometimes, causing operational problems. Glutaraldehyde, for example, is acutely toxic to aquatic organisms, mainly to freshwater fishes 15 , although it is usually considered a biodegradable biocide 4,6 . For these reasons, the use of alternative, environmentally friendly biocides is of great industrial interest.…”