Inhibition of Gas Hydrate Formation With a Hyperactive Insect Antifreeze Protein

Gas hydrates are crystalline, ice-like solids which can form from water and small molecules such as those present in natural gas. They form at low temperatures and moderate to high pressures, conditions frequently encountered in the oil and gas industry. Excessive formation of gas hydrates causes blockage of pipelines with subsequent loss of production. Several techniques are applied to avoid gas hydrate formation, but relatively recently, low dosage kinetic hydrate inhibitors (KHIs) have been developed. Despite the success of these compounds at very low concentrations, their poor biodegradability has prompted a search for new environmentally friendly hydrate inhibitors. Antifreeze proteins (AFPs) have been shown to be promising candidates for gas hydrate formation. In particular, certain insect AFPs express very high antifreeze activity (their ability to prevent ice from forming when cooled). Here we show that an insect antifreeze protein from the longhorn beetle, Rhagium mordax (RmAFP1), the most potent protein yet found for freezing inhibition, can inhibit methane hydrates as effectively as the synthetic polymeric inhibitor polyvinylpyrrolidone (PVP). In high pressure Rocking Cell experiments, onset hydrate nucleation temperatures and growth profiles showed highly repeatable results. RmAFP1 clearly showed inhibition of hydrates compared to amino acids (L-valine and L-threonine) and the protein Bovine Serum Albumin (BSA). This indicates that proteins or amino acids do not generally inhibit hydrate formation. The performance of RmAFP1 shows promising results as a new green KHI and could serve as the prototype for further development and increased production of green hydrate inhibitors.