Sulfate-reducing bacteria (SRB) have a unique ability to respire under anaerobic conditions using sulfate as a terminal electron acceptor, reducing it to hydrogen sulfide. SRB thrives in many natural environments (freshwater sediments and salty marshes), deep subsurface environments (oil wells and hydrothermal vents), and processing facilities in an industrial setting. Owing to their ability to alter the physicochemical properties of underlying metals, SRB can induce fouling, corrosion, and pipeline clogging challenges. Indigenous SRB causes oil souring and associated product loss and, subsequently, the abandonment of impacted oil wells. The sessile cells in biofilms are 1,000 times more resistant to biocides and induce 100-fold greater corrosion than their planktonic counterparts. To effectively combat the challenges posed by SRB, it is essential to understand their molecular mechanisms of biofilm formation and corrosion. Here, we examine the critical genes involved in biofilm formation and microbiologically influenced corrosion and categorize them into various functional categories. The current effort also discusses chemical and biological methods for controlling the SRB biofilms. Finally, we highlight the importance of surface engineering approaches for controlling biofilm formation on underlying metal surfaces.
A lignocellulolytic
and thermophilic bacterium Geobacillus sp. WSUCF1
was investigated for its production of biopolymers (exopolysaccharides,
EPSs) using agricultural waste corn stover. The maximum EPS production
achieved was 410 mg/L in a 40-L bioreactor. Four purified EPSs were
obtained: the two neutral EPSs were glucomannan and the two negatively
charged EPSs were mannan. The molecular weight of all four EPSs was
estimated to be approximately 1000 kDa, and their FTIR and NMR spectra
indicated that they were mainly composed of an α-type glycosidic
bond in a linear structure. The mannan EPSs had a low level of crystallinity
and displayed high thermal stability, with thermal degradation temperatures
of 309 and 316 °C, while the glucomannan EPSs were essentially
amorphous and had moderate thermal stability, with thermal degradation
temperatures of 203 and 227 °C. A mannan EPS (EPS 1–2)
showed exceptional biocompatibility, with a noncytotoxic concentration
as high as 4000 μg/mL using HEK-293 cell line. The green metrics
showed that EPS production using corn stover appears to be more sustainable
than using glucose. This study reports for the first time a cultivation
strategy for EPS production by a lignocellulolytic thermophile using
corn stover as a carbon source, requiring no biomass pretreatment.
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