Is Membrane Filtration Applicable for the Recovery of Biologically Active Substances from Spent Lavender?

This study explored the batch membrane filtration of 40% ethanol extracts from spent lavender, containing valuable compounds like rosmarinic acid, caffeic acid, and luteolin, using a polyamide-urea thin film composite X201 membrane. Conducted at room temperature and 20 bar transmembrane pressure, the process demonstrated high efficiency, with rejection rates exceeding 98% for global antioxidant activity and 93-100% for absolute concentrations of the target components. During concentration, the permeate flux declined from 2.43 to 1.24 L·m^-2·h^-1 as the permeate-to-retentate-volume ratio increased from 0 to 1. The process resistance, driven by osmotic pressure and concentration polarization, followed a power-law relationship with a power value of 1.20, consistent with prior nanofiltration studies of rosmarinic acid solutions. Notably, no membrane fouling occurred, confirming the method's scalability without compromising biological activity. The antioxidant activity, assessed via the DPPH method, revealed that the retentate exhibited double the activity of the feed. Antibacterial assays using broth microdilution showed that the retentate inhibited Escherichia coli by 73-96% and Bacillus subtilis by 97-98%, making it the most active fraction. These findings validate the effectiveness of the X201 membrane for concentrating natural antioxidants and antibacterial agents from lavender extract under sustainable operating conditions.