Fractionation of oligosaccharides by nanofiltration

Abstract

Two loose nanofiltration membranes (NF-CA-50 and NF-TFC-50) and one dense ultrafiltration membrane (UF-CA-1) were used to fractionate commercial oligosaccharide mixtures by applying diafiltration in a 'dead-end' filtration cell at 40 bar constant pressure with a maximum volume concentration ratio (VCR) of 6 at each fractionation. The rejections of a monosaccharide (glucose) and a disaccharide (lactose) were determined for each membrane; the results indicated that fractionation between these two sugars was possible using the two nanofiltration membranes. During the nanofiltration purification of a commercial oligosaccharide mixture, yields of 19% (w/w) for monosaccharides and 88% (w/w) for di-and oligosaccharides were obtained with the NF-TFC-50 membrane after four filtration steps, indicating that removal of the monosaccharides is possible with only minor losses of the oligosaccharide content of the mixture. The ultrafiltration membrane, at the same time, gave purification levels similar to the NF-TFC-50 membrane with fewer diafiltration steps but with higher losses of di-and oligosaccharides (12% (w/w) for monosaccharides and 53% (w/w) for di-and oligosaccharides on the third run). INTRODUCTIONThe food industry has recently shown increased interest in oligosaccharides as functional food ingredients owing to their proposed beneficial effects on human health. 1 Oligosaccharides are carbohydrates consisting of 2-10 linked monomer sugars and either occur naturally or are produced chemically or by enzymatic transglycosylation or controlled degradation reactions. 2 Oligosaccharides are increasingly included in foods for their prebiotic properties. A prebiotic is defined as a non-digestible food ingredient that beneficially affects the host by selectively stimulating the growth and/or activity of one or more of a limited number of bacteria in the colon (ie Bifidobacterium spp and Lactobacillus spp). 2 Certain oligosaccharides have also been reported to act as soluble dietary fibres and as anticarcinogenic agents. 2 Food-grade oligosaccharides are mixtures containing oligosaccharides of different degrees of polymerisation and monosaccharides. Not all of these sugars possess prebiotic activity and it would be useful to be able to separate the active oligosaccharides from the contaminants. This is particularly important when the materials are to be tested using in vitro models of the human gut, as these models test the fermentation of all carbohydrate material present, whereas in the human situation some components would not reach the colon.

Fractionation of a galacto-oligosaccharides solution at low and high temperature using nanofiltration

“…Finally, using the rejection fraction instead of concentrations, a relationship between observed rejection (R obs ) and real rejection (R real ) can be expressed as: (14) where R obs is defined as (15) Pruksasri et al Page 7 In a cross flow system, the mass transfer coefficient (k m ) can be calculated with the equation: (16) where Sh is the Sherwood number, Re the Reynolds number, Sc the Schmidt number, d h the hydraulic diameter and D the diffusion coefficient. The factors α i are filtration system related factors.…”

“…Currently, commercial GOS products are produced by the enzymatic reaction of concentrated lactose solutions at 200-400 g/L with β-galactosidase from different sources. Several purification techniques have been investigated such as precipitation by ethanol [9], adsorption by activated charcoal [10][11][12], separation by ion exchange chromatography [13] and membrane fractionation [14][15][16][17][18][19]. Nanofiltration is of particular interest because of its selectivity properties for the present application, thus, some studies have already been published [14][15][16][17][18][19].…”

Continuous Membrane Bioreactor (CMBR) to Produce Nanoparticles from Milk Components

“…Nanofiltration membranes can be used for purifying galactooligosaccharides (GOS) products from the monosaccharide hydrolysis products, glucose and galactose. According to Gosling et al, (2010), up to 88% of the di-and oligosaccharides were recovered from a commercial GOS mixture using a nanofiltration membrane with only 19% of the monosaccharides remaining in the retentate stream (Goulas et al, 2003). Catarino et al, (2008) investigated the fractionation of saccharide mixtures with calcium using ultrafiltration and nanofiltration processes and reported that saccharide fractionation was enhanced in the presence of calcium.…”

Experimental study of lactose hydrolysis and separation in cstr-uf membrane reactor

“…One possibility for ensuring protection of purified enzyme is offered by using membrane processes (Curcio et al, 2006). Therefore, an UF system in combination with a hydrolysis reactor might be preferred due to enzyme separation via the membrane (Goulas et al, 2003, Novain et al, 2005.…”