Cinnamaldehyde effectively disrupts Desulfovibrio vulgaris biofilms: potential implication to mitigate microbiologically influenced corrosion.

Abstract

Microbiologically influenced corrosion poses significant challenges to various industries, as metal surfaces degrade due to the formation of microbial biofilms. Sulfate-reducing bacteria (SRB) are key contributors to this process in anoxic environments (e.g., oil and gas pipelines), mainly by producing highly corrosive hydrogen sulfide. Current prevention methods involving biocides often have drawbacks such as high toxicity and disposal costs, calling for novel environmentally friendly alternatives. Essential oils with their antimicrobial properties and biodegradability may represent promising candidates against microbial corrosion. In this study, cinnamaldehyde was selected both for its antimicrobial activity and its well-documented role as a corrosion inhibitor; then, its antibiofilm activity was investigated against Desulfovibrio vulgaris, in comparison with the well-known reference biocide glutaraldehyde. Both compounds were bactericidal against D. vulgaris at 12.5 µg/mL. D. vulgaris biofilms were developed and monitored by confocal microscopy, and then 72-h-old biofilms were exposed to serial cinnamaldehyde and glutaraldehyde concentrations (12.5-100 µg/mL) for a further 48 h, to evaluate their disruptive effects. Both compounds caused a significant disruption of pre-formed biofilms, at 50 µg/mL. The reduction compared to the untreated controls was ca. 90% vs 85% for biomass, 60% vs 45% for average thickness, and 85% vs 80% for surface area, respectively. Interestingly, cinnamaldehyde applied to a D. vulgaris biofilm grown on representative metal coupons completely inhibited the recovery of viable adherent cells. These data, altogether, highlight the potential of cinnamaldehyde as an effective alternative for controlling and mitigating microbiologically influenced corrosion, with comparable efficacy to glutaraldehyde.IMPORTANCEThe increasing environmental and health concerns associated with the use of conventional biocides to manage and control microbiologically influenced corrosion highlight the need for eco-friendly alternatives. Sulfate-reducing bacteria (SRB) represent the main players in this process, by adhering and proliferating as biofilms on metal infrastructures, producing metabolites that accelerate corrosion. Essential oils have long been regarded as potent antimicrobials endowed with low toxicity; however, there is limited knowledge about their potential use against anaerobic bacteria responsible for corrosion. This study focuses on the antimicrobial activity of cinnamaldehyde and shows its efficacy in eradicating biofilm-grown D. vulgaris, a model species to study SRB energy metabolism. Notably, cinnamaldehyde is also a well-known corrosion inhibitor, which makes it an appealing candidate for industrial applications, particularly where SRB-induced corrosion is prevalent. Altogether, our results pave the way for the future development of green sustainable strategies involving the use of cinnamaldehyde to mitigate microbiologically influenced corrosion.