Theoretical Insight into the Biodegradation of Solitary Oil Microdroplets Moving through a Water Column

Abstract

In the aftermath of oil spills in the sea, clouds of droplets drift into the seawater column and are carried away by sea currents. The fate of the drifting droplets is determined by natural attenuation processes, mainly dissolution into the seawater and biodegradation by oil-degrading microbial communities. Specifically, microbes have developed three fundamental strategies for accessing and assimilating oily substrates. Depending on their affinity for the oily phase and ability to proliferate in multicellular structures, microbes might either attach to the oil surface and directly uptake compounds from the oily phase, or grow suspended in the aqueous phase consuming solubilized oil, or form three-dimensional biofilms over the oil–water interface. In this work, a compound particle model that accounts for all three microbial strategies is developed for the biodegradation of solitary oil microdroplets moving through a water column. Under a set of educated hypotheses, the hydrodynamics and solute transport problems are amenable to analytical solutions and a closed-form correlation is established for the overall dissolution rate as a function of the Thiele modulus, the Biot number and other key parameters. Moreover, two coupled ordinary differential equations are formulated for the evolution of the particle size and used to investigate the impact of the dissolution and biodegradation processes on the droplet shrinking rate.

The host generalist phytopathogenic fungus Sclerotinia sclerotiorum differentially expresses multiple metabolic enzymes on two different plant hosts

“…The families GH12, GH3, GH28 and GH16 are associated with the degradation of cellulose, beta-glycans, pectins 30 and hemicellulose respectively 43 (Table 3). These substrates are all well-known cell wall components across the plant kingdom, which raises the question of why certain CAZymes would be upregulated in specific hosts 44 . One possibility is that these differentially expressed CAZymes act on variants of cell-wall components peculiar to specific plant hosts.…”

Oil Spill Modeling: A Critical Review on Current Trends, Perspectives, and Challenges

“…This research has been incorporated into NOAA's GNOME oil spill model, by including a new biodegradation algorithm, which is dependent on the surface area of droplets [73]. Work performed by Kapellos [85] and Kapellos et al [86] on the effect of biofilm formation, including the development of a shrinking core model, has not yet found its way into operational oil spill models. A comparison of different modeling approaches for oil droplets biodegradation following a deep sea blowout is documented in [72], employing the TAMOC model [87], while the importance of initial oil droplet size distribution and biodegradation for the subsurface transport of oil spills is highlighted in the work of North et al [88] using LTRANS.…”

Impact of Microbial Uptake on the Nutrient Plume around Marine Organic Particles: High-Resolution Numerical Analysis

“…Interestingly, under controlled nutrient release, the eutrophic plume attenuates non-linearly with lowering release rate. For aggregates with marked spatial heterogeneity of bacterial activities, full resolution of the biochemical coupling between particle-associated and free-living bacteria would require to combine the present model formulation with models of intraparticle transport [ 24 , 44 ] and the concomitant biofilm dynamics [ 84 , 85 ].…”

“…For slow-moving microparticles, the flow around the particle is laminar with low Reynolds number, , where is the density of ambient water, is the dynamic viscosity of ambient water, and is the average velocity of ambient water relative to the particle. Thus, the radial and angular components of the dimensionless velocity vector, , are given by Stokes’ solution [ 24 ]: …”

“…Biofilm-forming bacteria colonize the particle surface and affect the rates of POM degradation and solubilization in multiple ways ( Figure 1 ). First, the extracellular polymeric matrix of the biofilm acts as a diffusive barrier and regulates the transport of solutes from the particle surface to ambient water, and vice versa [ 24 ]. Second, biofilm formers use exoenzymes and biosurfactants to transform refractory POM compounds into dissolved organic matter, part of which is taken up in the biofilm and the rest leaks out in ambient water [ 21 , 25 , 26 , 27 , 28 , 29 , 30 , 31 ].…”