Bacterial Inhibition of Methane Clathrate Hydrates Formed in a Stirred Autoclave

Abstract

The potential for hydrate inhibition in a stirred autoclave at a subcooling of 2.3 K has been tested on two bacterial isolates. Chryseobacterium sp. C14 survives multiple freeze−thaw events and inhibits ice recrystallization, and Escherichia coli has neither of these properties but is a biofilm producer. Both strains showed methane hydrate inhibition, with a significant reduction in total hydrate formed. Chryseobacterium delayed hydrate nucleating time, to a similar level found for the commercial kinetic inhibitor, polyvinylpyrrolidone (PVP; 0.2 wt %). However, in the presence of E. coli, in comparison to PVP, the time to nucleation was almost tripled and the hydrate growth rate was reduced by half. Because of the variation inherent with the microbial samples, likely a result of the complexities associated with varying cell numbers and metabolic activity, numerous experiments were required. Analysis of the distinct hydrate growth profiles shown by the two bacterial strains indicated that different molecular sources were likely responsible for the observed inhibition. As a working hypothesis, it is suggested that the inhibition observed by Chryseobacterium cultures was partially due to ice recrystallization inhibition properties, while that of E. coli may be due to secreted macromolecules and the effect of biofilm.

Gas hydrate inhibition by perturbation of liquid water structure

“…It is especially noteworthy in that there have been several previous reports of discrepancies between the nucleation and growth inhibition performances of KHIs3940. These discrepancies have been attributed to the fact that hydrate growth occurs on hydrate surfaces, whereas heterogeneous hydrate nucleation mostly initiates from solid nucleating impurities1.…”

Hydrophobic amino acids as a new class of kinetic inhibitors for gas hydrate formation

“…Firstly, the relationship between amino acid hydrophobicity and nucleation inhibition followed the same trend as for growth inhibition (Figs. 3c and 3d), while there have been several recent reports on differences in effectiveness of KHIs on nucleation and growth5556. This result is remarkable in that nucleation inhibitors interact with the foreign nucleating solid impurities, whereas growth inhibitors interact with the hydrate surface55.…”

Engineering Peptides to Catalyze and Control Stabilization of Gas Hydrates: Learning From Nature

“…Recent studies have shown that proteins and polypeptides produced by microorganisms, including an exported, extracytoplasmic porin-like protein from a marine methylotroph (dubbed “GHP1”), can accelerate methane hydrate formation under conditions simulating naturally occurring seafloor . Further, there are various accounts of experimental studies that have attempted to show biomolecules (including biosurfactants) regulating the kinetics of methane hydrate formation, but these studies are somewhat inconclusive. − …”