Eco-friendly polylactic acid/rice husk ash mixed matrix membrane for efficient purification of lysozyme from chicken egg white

Abstract

An eco-friendly and inexpensive ion-exchange membrane was developed for efficient purification of lysozyme from chicken egg white. Agricultural waste particles (rice husk ash, RHA) were incorporated into biodegradable polymeric matrix (polylatic acid, PLA) to fabricate porous PLA/RHA mixed matrix membrane (MMM) via water-vapour-induced phase inversion. The resulted membrane had an ion-exchange capacity (IEC) of 844 μmol/g membrane. In batch operation at pH 8, the protein adsorption equilibrium was attained within 2 h of contact time and the maximum lysozyme adsorption capacity was 4.49 μmol/g membrane. The adsorptivity of PLA/RHA MMM was essentially contributed from the filled RHA particles. In dynamic operation using one piece of PLA/RHA MMM at 122 L/h/m2 for a feed lysozyme concentration identical to that in mucin-free egg white (0.5 mg/mL), the breakthrough volume was about 50 MMM volume. The lysozyme recovery was 68–70% with a near 100% purity and a purification fold of 35 after an adsorption/washing/elution cycle treating mucin-free egg white mixture. The MMM performance was only deteriorated at a minor percentage during three successive cycles. These results demonstrate that the PLA/RHA MMM process is a green and efficient approach for isolating lysozyme from chicken egg white.