Comparison of Three Thermostable β-Glucosidases for Application in the Hydrolysis of Soybean Isoflavone Glycosides

Abstract

A novel thermostable β-glucosidase (Te-BglA) from Thermoanaerobacter ethanolicus JW200 was cloned, characterized and compared for its activity against isoflavone glycosides with two β-glucosidases (Tm-BglA, Tm-BglB) from Thermotoga maritima. Te-BglA exhibited maximum hydrolytic activity toward pNP-β-d-glucopyranoside (pNPG) at 80 °C and pH 7.0, was stable for a pH range of 4.6-7.8 and at 65 °C for 3 h, and had the lowest K(m) for the natural glycoside salicin and the highest relative substrate specificity (k(cat)/K(m))((salicin))/(k(cat)/K(m))((pNPG)) among the three enzymes. It converted isoflavone glycosides, including malonyl glycosides, in soybean flour to their aglycons more efficiently than Tm-BglA and Tm-BglB. After 3 h of incubation at 65 °C, Te-BglA produced complete hydrolysis of four isoflavone glycosides (namely, daidzin, genistin and their malonylated forms), exhibiting higher productivity of genistein and daidzein than the other two β-glucosidases. Our results suggest that Te-BglA is preferable to Tm-BglA and Tm-BglB, but all three enzymes have great potential applications in converting isoflavone glycosides into their aglycons.

Microbial β-Glucosidases: Screening, Characterization, Cloning and Applications

“…β-Glucosidase is also used in the hydrolysis of phenolic compounds such as flavonoids and isoflavone glycosides present in soybean, fruit, vegetables, and other plant-derived foods [156,206,207,208]. These compounds are known to have phytoestrogenic [209], antioxidant [210,211], anticancer [212], and antinflammatory activities [213].…”

A highly glucose-tolerant GH1 β-glucosidase with greater conversion rate of soybean isoflavones in monogastric animals

“…Based on the substrate specificity, β-glucosidases are grouped into aryl-β-glucosidase, true cellobiase, and β-glucosidase with broad substrate specificity [24, 30]. Those β-glucosidases acting on cellobiose and soybean isoflavones have important application values in the feed, food, biofuel and other fields [25, 32, 34]. One bottleneck of β-glucosidase application in the feed industry is its sensitivity to glucose, which is commonly assessed by measuring the half inhibitory concentration of glucose (IC 50 ) or inhibition constant ( K i ).…”

土曲霉来源的β-葡萄糖苷酶的酶学特性及其对大豆异黄酮的水解

“…1). Thus the enzyme was within the broad range of fungal β-glucosidase (35 to 250 kDa) (Song et al, 2011). …”

“…The productivity (mmol/(L·h)) of isoflavone aglycones was defined as the increase in the concentration produced in 1 h . The hydrolysis effect was calculated by the following equation (Song et al, 2011): hydrolysis rate=100%×(isoflavone glycosides in control samples−isoflavone glycosides in hydrolyzed samples)/isoflavone glycosides in the control samples.…”

“…Enzymatic hydrolysis of β-glucosidase towards soybean isoflavone is an important application in the food and feed industry, which has been investigated by direct use of β-glucosidase from plants and microorganisms (Chuankhayan et al, 2007;Kaya Yang et al, 2009;Song et al, 2011;Kim et al, 2012;Fang et al, 2014;Fujita et al, 2015). However, low solubility of isoflavones reduces the productivity of isoflavone aglycones in industrial production (Horii et al, 2009).…”