99
improve solubilisation of β-glucan. Ultrasound assisted extraction have also been
reported to be an efficient process to extract high molecular weight β-glucans from
barley. The maximum extraction yield (66.1%) was reported to be achieved when
delivering the maximum amount of energy (962.5 kJ/L), leading at the same time to
the lowest MW (269 kDa). A reduction in the intensity of the treatment (energy
output of 170 kJ/L) decreases the extraction yield up to 44.3% but increases the
β-glucan MW to 461 kDa (Benito-Román et al. 2013). Recently, Sourki et al. (2017)
reported that with increasing sonication time up to 5.5 min, β-d-glucan flow behaviour index (n) and its extraction yield significantly increased.
Microwave Extraction
Microwave energy is a non-ionizing type of electromagnetic radiation with wavelengths typically in the range of 1 mm to 1 m, corresponding to 0.3–300 GHz. MAE
was employed for the polysaccharide extraction from the fruiting body of Hericium
erinaceum mushroom. Comparison of the results obtained by MAE with those
obtained by conventional hot-water extraction revealed that the extractability of the
former for 5 min at 140 °C was almost equivalent to that of the latter extraction for
6 h at 100 °C (Ookushi et al. 2006). Besides, microwave treatments have also been
found to increase the solubilization of polysaccharide. It is reported that microwave
heating in a high-pressure vessel improves the dispersion of β-glucan solution in
water without polymer degradation (Wang et al. 2002). A water insoluble hyperbranched β-glucan isolated from sclerotia of Pleurotus tuberregium was treated by
microwave heating to produce an aqueous solution, and the soluble polysaccharide
existed in a sphere-like conformation in 0.02% aqueous sodium azide solution (Tao
and Xu 2008).
Purification of Beta-Glucan
During β-glucan extraction, water or other solvents are used. However, impurities
(protein-based or non-starch polysaccharides) are present in solutions during these
treatments, thus, polysaccharide enriched extracts obtained from the extraction procedure are further purified. Ion-exchange chromatography and gel filtration chromatography are the most common and convenient methods for purifying
polysaccharide. In general, the impurities are removed from the polysaccharide
through ethanol precipitation, neutral polysaccharides are separated from acidic
ones using ion-exchange chromatography through DEAE-cellulose columns, and
the neutral polysaccharides are then separated into α-glucan and β-glucan using gel
filtration and affinity chromatography (Wasser 2002). Using cetyl trimethyl ammonium bromide or cetyl pyridinum chloride, acidic and neutral polysaccharide might
even be separated which then form a precipitated complex with the acidic polysacBeta-Glucans
improve solubilisation of β-glucan. Ultrasound assisted extraction have also been
reported to be an efficient process to extract high molecular weight β-glucans from
barley. The maximum extraction yield (66.1%) was reported to be achieved when
delivering the maximum amount of energy (962.5 kJ/L), leading at the same time to
the lowest MW (269 kDa). A reduction in the intensity of the treatment (energy
output of 170 kJ/L) decreases the extraction yield up to 44.3% but increases the
β-glucan MW to 461 kDa (Benito-Román et al. 2013). Recently, Sourki et al. (2017)
reported that with increasing sonication time up to 5.5 min, β-d-glucan flow behaviour index (n) and its extraction yield significantly increased.
Microwave Extraction
Microwave energy is a non-ionizing type of electromagnetic radiation with wavelengths typically in the range of 1 mm to 1 m, corresponding to 0.3–300 GHz. MAE
was employed for the polysaccharide extraction from the fruiting body of Hericium
erinaceum mushroom. Comparison of the results obtained by MAE with those
obtained by conventional hot-water extraction revealed that the extractability of the
former for 5 min at 140 °C was almost equivalent to that of the latter extraction for
6 h at 100 °C (Ookushi et al. 2006). Besides, microwave treatments have also been
found to increase the solubilization of polysaccharide. It is reported that microwave
heating in a high-pressure vessel improves the dispersion of β-glucan solution in
water without polymer degradation (Wang et al. 2002). A water insoluble hyperbranched β-glucan isolated from sclerotia of Pleurotus tuberregium was treated by
microwave heating to produce an aqueous solution, and the soluble polysaccharide
existed in a sphere-like conformation in 0.02% aqueous sodium azide solution (Tao
and Xu 2008).
Purification of Beta-Glucan
During β-glucan extraction, water or other solvents are used. However, impurities
(protein-based or non-starch polysaccharides) are present in solutions during these
treatments, thus, polysaccharide enriched extracts obtained from the extraction procedure are further purified. Ion-exchange chromatography and gel filtration chromatography are the most common and convenient methods for purifying
polysaccharide. In general, the impurities are removed from the polysaccharide
through ethanol precipitation, neutral polysaccharides are separated from acidic
ones using ion-exchange chromatography through DEAE-cellulose columns, and
the neutral polysaccharides are then separated into α-glucan and β-glucan using gel
filtration and affinity chromatography (Wasser 2002). Using cetyl trimethyl ammonium bromide or cetyl pyridinum chloride, acidic and neutral polysaccharide might
even be separated which then form a precipitated complex with the acidic polysacBeta-Glucans