Extraction of steviol glycosides using novel cellulose acetate pthalate (CAP) – Polyacrylonitrile blend membranes

Abstract

Tailor made membranes cast from blend of cellulose-acetate pthalate (CAP) and polyacrylonitrile (PAN) polymers for the extraction of steviol glycosides is the point of focus of this study. The mentioned blend is a highly non-ideal and immiscible and membranes formed using this blend is not reported in the literature. Various weight percent combinations of the polymers were dissolved in an aprotic solvent, viz., dimethylacetamide (DMAc) and membranes were cast using the phase inversion method. The obtained membranes were characterized on basis of molecular weight cut off (MWCO), hydraulic permeability, hydrophilicity, pore density, porosity, surface morphology and mechanical strength. It was found that a set of membranes of various MWCO was obtained ranging from 7kDa to 104kDa for various compositions of the blend. Stevioside and Rebaudioside were then recovered from water extract of dry Stevia leaf powder using these ultrafiltration membranes. The permeate flux decline was analyzed for each of the membranes, to study the fouling characteristics. The optimum membrane was identified in terms of steady state permeate flux, recovery and purity of glycosides. It was found that the 90kDa membrane yielded the maximum steady state flux of 11 L/m2hr, recovery of 68% and purity of 34%.