Enzymatic Hydrolysis of Triglycerides at the Water–Oil Interface Studied via Interfacial Rheology Analysis of Lipase Adsorption Layers

Abstract

The enzymatic hydrolysis of sunflower oil occurs at the water–oil interface. Therefore, the characterization of dynamic interfacial phenomena is essential for understanding the related mechanisms for process optimizations. Most of the available studies for this purpose deal with averaged interfacial properties determined via reaction kinetics and dynamic surface tension measurements. In addition to the classical approach for dynamic surface tension measurements, here, the evolution of the dilational viscoelasticity of the lipase adsorbed layer at the water–oil interface is characterized using profile analysis tensiometry. It is observed that lipase exhibits nonlinear dilational rheology depending on the concentration and age of the adsorbed layer. For reactive water–oil interfaces, the response of the interfacial tension to the sinusoidal area perturbations becomes more asymmetric with time. Surface-active products of the enzymatic hydrolysis of triglycerides render the interface less elastic during compression compared to the expansion path. The lipolysis products can facilitate desorption upon compression while inhibiting adsorption upon expansion of the interface. Lissajous plots provide an insight into how the hysteresis effect leads to different interfacial tensions along the expansion and compression routes. Also, the droplet shape increasingly deviates from a Laplacian shape, demonstrating an irreversible film formation during aging and ongoing hydrolysis reaction, which supports our findings via interfacial elasticity analysis.

Orientation and Conformation of Hydrophobin at the Oil–Water Interface: Insights from Molecular Dynamics Simulations

“…Protein surfactants have widely emerged in the food, petroleum, mining, cosmetic, pharmaceutical, and chemical industries, − ascribed to their high surface activity, nontoxicity, abundant nutriments, benign biocompatibility, and marvelously environment-friendly property. , Interestingly, they are naturally amphiphilic, which determines their crucial function in reducing surface tensions and stabilizing oil–water emulsions . Recently, studies on protein adsorption at the oil–water interface have been comprehensively reviewed. − They argued that because of the high surface activity, hydrophobins are the most desirable candidate as emulsifiers rather than globular whey proteins and other synthetic emulsifiers commonly used in the food industry. , Hence, hydrophobins have been extensively applied in a wide range of industries such as emulsion production, petroleum recovery, and biomedical material preparation. ,,, …”

“…10,11 Hence, hydrophobins have been extensively applied in a wide range of industries such as emulsion production, petroleum recovery, and biomedical material preparation. 7,8,12,13 Hydrophobins are a class of small proteins (about 10 kDa) expressed by filamentous fungi, which generally possess a hydrophobic patch implementing a high surface activity and four intramolecular disulfide bonds crosslinked by eight cysteines stabilizing the overall structure of hydrophobins in solution. 14 Hydrophobins can be further categorized into two species according to the solubility difference.…”

Prokaryotic Expression and Enzymatic Properties of Lipase from Schizochytrium Pombe

“…Surfactants can increase the contact surface at the oil-water interface and thus have a beneficial effect on lipase catalytic efficiency [30][31][32]. The specific targeting of different types of lipases would also have different effects.…”

Effect of Oil Polarity on the Protein Adsorption at Oil–Water Interfaces

“…When proteins are adsorbed at oil–water interfaces, the hydrophobic parts of proteins generally orient toward and even partly penetrate the oil phase. The subsequent conformational changes also allow proteins to reduce the interfacial tensions of oil–water systems and eventually to form a viscoelastic layer for protein-emulsified performance and catalyzed activity . The protein adsorption orientation and conformation , are largely affected by protein structures and the oil polarity .…”