Lipid hydrolysis monitoring in wastewater treatment: proof-of-concept for a high throughput vegetable oil emulsion based assay

Lipids are one of the main organic components in industrial and municipal wastewaters. Lipid hydrolysis is the first step in the biological conversion process and requires a close contact between lipid emulsion droplets and microbial hydrolytic enzymes. Adequate lipid hydrolysis monitoring is crucial to obtain mechanistic knowledge on lipid hydrolysis in response to changes in the process conditions and to improve the overall lipid conversion efficiency in aerobic and anaerobic wastewater treatment systems. We set out to develop a high-throughput lipid hydrolysis monitoring method based on vegetable oil model substrates and fluorescent quantification of product formation by exploiting the interaction with Rhodamine B. Olive oil and soybean oil emulsions were prepared with a high interfacial area and acceptable emulsion stability. The method was easy to apply and allowed to obtain detailed kinetic data over a time course of several hours for up to 16 samples in parallel. A proof-of-concept was obtained with a commercial enzyme, Amano lipase, but remains to be provided for wastewater treatment sludge samples. The findings of this study pave the way for further method development in lipid hydrolysis monitoring.

Lysis of membrane lipids promoted by small organic molecules: Reactivity depends on structure but not lipophilicity

Several organic molecules of low molecular weight (<150 Da) are demonstrated to have substantial membrane-lytic potential despite having a low predicted lipophilicity (logD < 1 at neutral pH). In aqueous liposome dispersions, 38 aromatic compounds were tested for their ability to either promote lipid hydrolysis or directly participate in chemical reactions with lipid molecules. Behaviors observed included acyl transfer from the lipid to form a lipidated compound, both with and without concomitant lysolipid formation; increases in the rate of lipid hydrolysis without lipidation; and no reactivity. The variation in activity, including a notably higher activity for heterocycles such as amino-substituted benzimidazoles and indazoles, demonstrates the potential to predict or “design-in” lytic activity once the rules that govern reactivity are better understood. The nature of this chemical instability has significant ramifications for the use or presence of lipids in diverse fields such as materials chemistry, food chemistry, and cell physiology.

Controlling lipid intestinal digestibility using various oil structuring mechanisms

This research demonstrates the ability to direct the rate and extent of lipid hydrolysis of oleogels using a combination of different structuring agents.