95
suggested such as hot water extraction (Benito-Román et al. 2011), acidic extraction (Ahmad et al. 2010), alkaline extraction (Ahmad et al. 2010; Din et al. 2009),
enzymatic extraction (Ahmad et al. 2010; Li et al. 2006), ultrasound-assisted extraction (UAE) (Benito-Román et al. 2013), and microwave extraction (Ookushi et al.
2006). Among these methods, UAE represents larger potency as this technique is a
cost- effective, quick, easy and efficient method that lessens the extraction time
compared to conventional methods (Maran and Priya 2014).
Hot-Water Extraction
Water extraction is the most generally used traditional method for extracting polysaccharide because of its potency in getting polysaccharides and its low cost.
Extraction time, extraction temperature, and also the ratio of water volume to raw
material weight play a key role in the extraction process of polysaccharide. Usually,
the lipid component and some other low-molecular weight substances in the raw
material are removed firstly by using 75–95% (V/V) ethanol through a reflux divider
(Li et al. 2013a, b). Then the residue is subsequently dried and extracted with boiling water many times. The extracting liquids are separated and collected by centrifugation. Various scientists adopted this method for the extraction of β-glucan. In
a study, Morgan and Ofman (1998) attempted the hot water extraction process with
the incorporation of a modification of freeze–thaw cycles. Using this technique,
greater recovery of β-glucan along with elevated level of purity can be obtained.
However, polysaccharide extraction from fungus remains a serious issue, as a
result of they are heterogeneous with less solubility in water, and also the yield of
water extraction is often quite low. One of the most promising approaches is pressurized water extraction (PWE) because it presents necessary significances over
traditional hot-water extractions. The solvents are at high temperature and high
pressure throughout the PWE method. There is larger solubility and larger diffusion
rate at high temperature, while the solvents remain below its boiling point at high
pressure (Villares et al. 2012). For example, Palanisamy et al. (2014) reported that
an optimal extraction condition for cultivated mushrooms (Agaricus bisporus,
Lentinus edodes and Pleurotus ostreatus) is 200 °C, and 5 cycles of 5 min each at
10.3 MPa. Similarly, there is maximum recovery for extraction of α-(1,4)-glucans,
and β-(1,6)-glucans at a pressure of 10.1 MPa for 70 min at 28 °C (Lo et al. 2007).
Alkaline Extraction
Non-cereal sources may vary slightly in β-glucan extraction because the compositions of these sources are variable in nature. This condition is found in case of yeast,
molds, and mushrooms from which β-glucan can be extracted. Alkaline treatment
favors this kind of extraction as this kind of β-glucan has different chemical composition. To extract β-glucan, the cell mass is treated with a high concentration of
alkali (1 M KOH) at low temperature for a long period of time with continuous
Beta-Glucans
suggested such as hot water extraction (Benito-Román et al. 2011), acidic extraction (Ahmad et al. 2010), alkaline extraction (Ahmad et al. 2010; Din et al. 2009),
enzymatic extraction (Ahmad et al. 2010; Li et al. 2006), ultrasound-assisted extraction (UAE) (Benito-Román et al. 2013), and microwave extraction (Ookushi et al.
2006). Among these methods, UAE represents larger potency as this technique is a
cost- effective, quick, easy and efficient method that lessens the extraction time
compared to conventional methods (Maran and Priya 2014).
Hot-Water Extraction
Water extraction is the most generally used traditional method for extracting polysaccharide because of its potency in getting polysaccharides and its low cost.
Extraction time, extraction temperature, and also the ratio of water volume to raw
material weight play a key role in the extraction process of polysaccharide. Usually,
the lipid component and some other low-molecular weight substances in the raw
material are removed firstly by using 75–95% (V/V) ethanol through a reflux divider
(Li et al. 2013a, b). Then the residue is subsequently dried and extracted with boiling water many times. The extracting liquids are separated and collected by centrifugation. Various scientists adopted this method for the extraction of β-glucan. In
a study, Morgan and Ofman (1998) attempted the hot water extraction process with
the incorporation of a modification of freeze–thaw cycles. Using this technique,
greater recovery of β-glucan along with elevated level of purity can be obtained.
However, polysaccharide extraction from fungus remains a serious issue, as a
result of they are heterogeneous with less solubility in water, and also the yield of
water extraction is often quite low. One of the most promising approaches is pressurized water extraction (PWE) because it presents necessary significances over
traditional hot-water extractions. The solvents are at high temperature and high
pressure throughout the PWE method. There is larger solubility and larger diffusion
rate at high temperature, while the solvents remain below its boiling point at high
pressure (Villares et al. 2012). For example, Palanisamy et al. (2014) reported that
an optimal extraction condition for cultivated mushrooms (Agaricus bisporus,
Lentinus edodes and Pleurotus ostreatus) is 200 °C, and 5 cycles of 5 min each at
10.3 MPa. Similarly, there is maximum recovery for extraction of α-(1,4)-glucans,
and β-(1,6)-glucans at a pressure of 10.1 MPa for 70 min at 28 °C (Lo et al. 2007).
Alkaline Extraction
Non-cereal sources may vary slightly in β-glucan extraction because the compositions of these sources are variable in nature. This condition is found in case of yeast,
molds, and mushrooms from which β-glucan can be extracted. Alkaline treatment
favors this kind of extraction as this kind of β-glucan has different chemical composition. To extract β-glucan, the cell mass is treated with a high concentration of
alkali (1 M KOH) at low temperature for a long period of time with continuous
Beta-Glucans