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

Abstract

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. Highlights Lipid hydrolysis monitoring is essential to optimize (an)aerobic wastewater treatment.; High-throughput monitoring methods are required.; The established p-nitrophenol palmitate method is not adequate.; A lipid assay model substrate should resemble the actual lipids present in wastewater.; Fluorescent lipid hydrolysis quantification with Rhodamine B is a promising approach for high-throughput monitoring.;

Keywords

• biological wastewater treatment
• enzyme activity
• hydrolysis
• lipids
• rhodamine b