Partial purification of quorum quenching (QQ) enzyme lactonase and membrane applications

Abstract

Biofouling is a significant challenge in membrane systems, caused by the accumulation of microorganisms and their secreted substances on membrane surfaces, leading to reduced efficiency and performance. Current strategies for mitigating biofouling, including pre-treatment and chemical cleaning methods, are often insufficient and environmentally unsustainable. Quorum Quenching (QQ) technology, which disrupts microbial communication pathways and inhibits biofilm formation, has emerged as a promising solution. This thesis investigates the use of partial purified lactonase enzyme, a QQ enzyme, to control biofouling in thin-film composite reverse osmosis (TFC-RO) membranes. The study started with the fabrication of TFC-RO membranes using phase inversion for support layer production, followed by interfacial polymerization to develop the active layer. Three different procedures were tested to make the membranes most efficient with the %18 PES-Method-2 as the configuration selected based on better filtration performance and structure properties. The membranes were identified through contact angle (CA), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) analyses. Partially purified lactonase enzyme was prepared from Bacillus sp. T5 with ammonium sulfate precipitation, partially purified. Enzyme activity tests were carried out at various temperature (4°C, 25°C, 37°C) and pH (5.5, 7, 8.5) and found to be in optimum at 25°C and pH 7 respectively. The enzyme was immobilized onto ACA-modified TFC-RO membranes using the chemical crosslinking process. Process achieved enzyme immobilization efficiencies up to 90% which showed effectiveness of process. The performance of the immobilized membranes was tested via biofouling (using Escherichia coli (E. coli) as a model organism). The results illustrated that immobilization of enzyme promoted fouling resistance whereby they had retained higher flux values and salt rejection efficiencies post biofouling than bare membranes. The results of antimicrobial activity tests and confocal microscope images verified that immobilized membranes inhibited bacterial growth. Finally, this thesis was able to develop TFC-RO membranes functionalized with partial purified lactonase enzyme in order to control biofouling. The identified outcomes emphasize the promise of this novel methodology for enhancing membrane performance, and overcoming biofouling-related impediments in water treatment systems.