Abstract
Ceramic and polymeric membrane systems were compared at the pilot scale for separating agave fructans into different molecular weight fractions that help to diversify them into more specific industrial applications. The effect of the transmembrane pressure of ultrafiltration performance was evaluated through hydraulic permeability, permeate flux and rejection coefficients, using the same operating conditions such as temperature, feed concentration and the molecular weight cut-off (MWCO) of membranes. The fouling phenomenon and the global yield of the process were evaluated in concentration mode. A size distribution analysis of agave fructans is presented and grouped by molecular weight in different fractions. Great differences were found between both systems, since rejection coefficients of 68.6% and 100% for fructans with degrees of polymerization (DP) > 10, 36.3% and 99.3% for fructooligosaccharides (FOS) and 21.4% and 34.2% for mono-disaccharides were obtained for ceramic and polymeric membrane systems, respectively. Thus, ceramic membranes are better for use in the fractionation process since they reached a purity of 42.2% of FOS with a yield of 40.1% in the permeate and 78.23% for fructans with DP > 10 and a yield of 70% in the retentate. Polymeric membranes make for an efficient fructan purification process, eliminating only mono-disaccharides, and reaching a 97.7% purity (considering both fructan fractions) with a yield of 64.3% in the retentate.
Highlights
Native agave fructans are a heterogeneous mixture of branched fructose polymers, linked by glycosidic linkages of fructose–fructose β (2−1) and β (2−6), with intermediate or terminal glucose units with degrees of polymerization (DP) between three and 29 [1]
0.56 and ending at 0.2 solute mol·h−1 ·m−2. These results show how the hydrodynamic conditions in the systems mainly affect the larger molecules (Fc and FOS), forcing their passage through the ceramic membrane, but not in the polymeric membrane, while mono- and disaccharides are the smallest solutes with free passage through different membranes
Great performance differences were found in our comparison of ceramic and polymeric membrane systems for the tight UF of agave fructans
Summary
Native agave fructans are a heterogeneous mixture of branched fructose polymers, linked by glycosidic linkages of fructose–fructose β (2−1) and β (2−6), with intermediate or terminal glucose units with degrees of polymerization (DP) between three and 29 [1] These fructans have potential applications due to their proven beneficial effects on human health, such as the prebiotic effect, as well as decreasing the body mass index, total body fat and triglyceride levels [2,3,4,5] and their technological applications as encapsulating agents and as substitutes for fat in food [6,7,8,9,10]. Separation using tight UF membranes (from 1 to 3 kDa) becomes more complex because it combines the sieving effect and Donnan exclusion, like the phenomenon that dominates the nanofiltration process (from 200 Da to 1 kDa)
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