Dead-end ultrafiltration of rich glucosinolates juice extracted from mustard defatted meal: Effects of operating conditions on permeate quality and membrane fouling

Abstract

Glucosinolates (GSL) (β-thioglucoside-N-hydroxysulfates) are rich-sulfur secondary metabolites with high reactive biological properties interesting for biofumigation. Brown mustard (Brassica juncea) seeds are rich in GSL mainly in sinigrin (≈100 μmol/g DM) and gluconapin (≈12 μmol/g DM). GSL should be extracted in their native form and then purified to be used as natural biopesticide. In this work, dead-end ultrafiltration of a rich glucosinolates juice expressed from defatted seed meal was studied and optimized by tuning experimental conditions. The impact of membrane MWCO (5–150 kDa), operating pressure (1–5 bar) and stirring (0–600 rpm) on the filtration kinetic and the permeate quality were studied. In the optimal conditions, most of impurities (proteins, colloids) were removed and the juice purity was increased from 35.2% to 90.1% without degrading the GSL. Modeling showed that the fouling mechanism is strongly depending on the applied stirring velocity. More importantly, fouling has been efficiently removed after membrane chemical cleaning using NaOH solution for membrane regeneration. The purified permeate rich in glucosinolates is very suitable for biopesticides formulation and the retentate concentrated in proteins may be valorized as animal feeding.