Effect of m-PEG modification on the properties and structure of recombinant lipase from Aspergillus niger GZUF36

Abstract

Natural lipase is challenging to meet industrial demands because of its low activity, poor stability, and intolerance to organic solvents. Our research aimed to improve the catalytic performance of the extracellular lipase from Aspergillus niger GZUF36 (PEXANL1) by modifying it with a molecular weight of 5000 monomethoxy polyethylene glycol (m-PEG5000) activated by p-toluenesulfonyl chloride (m-PEG5000-OTe). After modification of PEXANL1 with m-PEG5000-OTe (m-PEG5000-OTe@PEXANL1), the activity of m-PEG5000-OTe@PEXANL1 increased by 2.38-fold, its stability at high temperatures improved, and the optimal pH shifted towards the neutral region (pH 6). The effect of surfactants Triton X-100, Tween 20, Tween 80, and SDS on the enzyme activity of m-PEG5000-OTe@PEXANL1 was 118.44%, 124.28%, 120.40%, and 108.53%, respectively. They all activated the enzyme activity. Additionally, m-PEG5000-OTe@PEXANL enhanced its tolerance in organic solvents such as xylene and isopropanol. We analyzed the electrostatic interactions using Zeta potential and characterized the secondary structure using circular dichroism (CD) spectroscopy. The results indicated that the chemical modification led to structural changes in PEXANL1, enhancing its performance. The m-PEG5000-OTe@PEXANL1 may be used to synthesize healthy lipid 1, 3-diglyceride. That study laid the foundation for further industrial applications of PEXANL1 or other lipase by improving the catalytic performance of lipase through chemical modification.