Abstract
Glycyrrhetic acid 3-O-mono-β-d-glucuronide (GAMG) as an important derivative of glycyrrhizin (GL) shows stronger biological activities and higher sweetness than GL. The biotransformation process is considered as an efficient strategy for GAMG production, due to its mild reaction, high production efficiency and environmentally friendly status. In this study, licorice straw was used for the first time as a medium for GAMG and lignocellulosic enzyme production via solid-state fermentation (SSF) of endophytic fungus Chaetomium globosum DX-THS3. The fermentation conditions including particle size, temperature, seed age, inoculum size, and moisture of substrate were optimized. Furthermore, additional nitrogen sources and carbon sources were screened for GAMG production by C. globosum DX-THS3 of SSF. Under optimal fermentation conditions, the percent conversion of glycyrrhizin reached 90% in 15 days, whereas the control needed 35 days to achieve the same result. The productivity of optimization (P = 2.1 mg/g/day) was 2.33-fold that of non-optimization (P = 0.9 mg/g/day). Meanwhile, high activities of filter paper enzyme (FPase) (245.80 U/g), carboxymethyl cellulase (CMCase) (33.67 U/g), xylanase (83.44 U/g), and β-glucuronidase activity (271.42 U/g) were obtained faster than those in the control during SSF. Our study provides a novel and efficient strategy for GAMG production and indicates C. globosum DX-THS3 as a potential producer of lignocellulolytic enzymes.
Highlights
Glycyrrhizin (GL) is a major bioactive component of industrial crop Glycyrrhiza (Pandey and Ayangla 2017) with numerous valuable physiological properties, including antioxidative (Michaelis et al 2011), antiviral (Ito et al 1988), anticancer (Huang et al 2016), and antiinflammatory (Wang et al 2015a) action
One is the two-stage strategy for Glycyrrhetic acid 3-O-mono-β-d-glucuronide (GAMG) production, that is, GUS was firstly produced by fermentation of filamentous fungus such as P. purpurogenum Li-3 (Zou et al 2013) and Talaromyces pinophilus (Xu et al 2018a, b), and GAMG was produced by bio-transforming GL with GUS
An endophytic fungus C. globosum DX-THS3 was isolated from Dongxiang wild rice (Wang et al 2015b), and a GUS with specificity and highly transformable GL to generate GAMG was screened from this strain (Zhang et al 2020)
Summary
Glycyrrhizin (GL) is a major bioactive component of industrial crop Glycyrrhiza (Pandey and Ayangla 2017) with numerous valuable physiological properties, including antioxidative (Michaelis et al 2011), antiviral (Ito et al 1988), anticancer (Huang et al 2016), and antiinflammatory (Wang et al 2015a) action. Efficient approaches for large-scale GAMG production are unavailable far. Chemical approaches generally present several disadvantages, including the requirement of strong and harsh conditions, ineffective costs, poor selectivity, and environmental pollution (Brieskorn and Lang 1978). The biosynthesis of GAMG significantly has more potential and advantages because of its excellent substrate selectivity, high yields, mild reaction conditions, and eco-friendly status. The efficient biosynthesis of GAMG involves the use of β-glucuronidase (GUS) (Zou et al 2013; Xu et al 2018a, b; Wang et al 2013; Park et al 2005). GUSs are mainly screened from microorganisms (Zou et al 2013; Xu et al 2018a, b; Wang et al 2013; Park et al 2005). The isolation of GUS for biosynthesis of GAMG has several challenges, such as complicated processes and harsh cultivation conditions. An efficient, simple, and feasible approach for the production of GAMG must be developed
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