The Pioneering Role of Natural-Occurring Peptides on Methane Hydrate Formation—Insights from Experiments and Numerical Simulations

Abstract

Methane hydrates are the most abundant clathrates found in the environment, predominantly in the permafrost and marine continental margins. As such, they consitute an energy resource, a concern for climate change, as well as a potentially significant source of carbon for microorganisms. However, relatively little is known about the way that these microorganisms interact, if at all, with methane hydrate deposits in their environment. Recently, a porin produced by a marine methylotroph (Methylophaga aminisulfidivorans) was found to promote hydrate formation in conditions mimicking that of the seafloor. A specific peptide sequence (TAFDGGS) was shown to be at least partially responsible for this behaviour. However, the exact physico-chemical mechanisms underlying such effects are still unclear. Our research employed a dual methodology, integrating experimental procedures with molecular dynamics simulations to answer the question of how naturally occurring peptides can influence methane hydrate formation. Initially, laboratory experiments were conducted to observe the kinetics of methane hydrate formation in the presence of the selected natural peptide (TAFDGGS) and the traditional hydrate promoter: sodium dodecyl sulfate (SDS). Methane hydrate formation from deionized water served as a reference. Parameters such as rate of formation, induction time and total gas consumption were meticulously recorded and analysed. In parallel, molecular dynamics simulations of the hydrate formation process with and without the peptide were carried out. The careful analysis of the interactions between water, methane and the peptide provided molecular-level insights on how peptides can influence the nucleation and growth of methane hydrate clusters. Our results indicate that the natural peptide exhibits a distinctive promoting effect on the formation kinetics of methane hydrates. However, the mechanistic hypothesis that the promotion effect is achieved by providing more nucleation sites was ruled out by comparison with the reference groups. Instead, the results suggest a more complex biocatalytic effect on hydrate kinetics. These findings suggest a potential for peptides as eco-friendly alternatives to traditional chemical promoters in methane hydrate research and provide valuable insights into the design of more efficient and sustainable bio-based promoters. More fundamentally, this study lays a solid foundation for our understanding of the interactions between peptides and hydrates in nature and paves the way for further research on the role of proteins or microorganisms on hydrate deposits.