Induction and Catabolite Repression of beta-Glucosidase Synthesis in Myceliophthora thermophila D-14 (= ATCC 48104)

Biocatalysis of Platycoside E and Platycodin D3 Using Fungal Extracellular β-Glucosidase Responsible for Rapid Platycodin D Production

Platycodi radix (i.e., Platycodon grandiflorum root) products (e.g., tea, cosmetics, and herbal supplements) are popular in East Asian nutraceutical markets due to their reported health benefits and positive consumer perceptions. Platycosides are the key drivers of Platycodi radixes' biofunctional effects; their nutraceutical and pharmaceutical activities are primarily related to the number and varieties of sugar side-chains. Among the various platycosides, platycodin D is a major saponin that demonstrates various nutraceutical activities. Therefore, the development of a novel technology to increase the total platycodin D content in Platycodi radix extract is important, not only for consumers' health benefits but also producers' commercial applications and manufacturing cost reduction. It has been reported that hydrolysis of platycoside sugar moieties significantly modifies the compound's biofunctionality. Platycodi radix extract naturally contains two major platycodin D precursors (platycoside E and platycodin D3) which can be enzymatically converted to platycodin D via β-d-glucosidase hydrolysis. Despite evidence that platycodin D precursors can be changed to platycodin D in the Platycodi radix plant, there is little research on increasing platycodin D concentrations during processing. In this work, platycodin D levels in Platycodi radix extracts were significantly increased via extracellular Aspergillus usamii β-d-glucosidase (n = 3, p < 0.001). To increase the extracellular β-d-glucosidase activity, A. usamii was cultivated in a culture media containing cellobiose as its major carbon source. The optimal pH and temperature of the fungal β-d-glucosidase were 6.0 and 40.0 °C, respectively. Extracellular A. usamii β-d-glucosidase successfully converted more than 99.9% (w/v, n = 3, p < 0.001) of platycoside E and platycodin D3 into platycodin D within 2 h under optimal conditions. The maximum level of platycodin D was 0.4 mM. Following the biotransformation process, the platycodin D was recovered using preparatory High Performance Liquid Chromatography (HPLC) and applied to in vitro assays to evaluate its quality. Platycodin D separated from the Platycodi radix immediately following the bioconversion process showed significant anti-inflammatory effects from the Lipopolysaccharide (LPS)-induced macrophage inflammatory responses with decreased nitrite and IL-6 production (n = 3, p < 0.001). Taken together, these results provide evidence that biocatalysis of Platycodi radix extracts with A. usamii may be used as an efficient method of platycodin D-enriched extract production and novel Platycodi radix products may thereby be created.

Highly Selective Bioconversion of Ginsenoside Rb1 to Compound K by the Mycelium of Cordyceps sinensis under Optimized Conditions

Compound K (CK), a highly active and bioavailable derivative obtained from protopanaxadiol ginsenosides, displays a wide variety of pharmacological properties, especially antitumor activity. However, the inadequacy of natural sources limits its application in the pharmaceutical industry. In this study, we firstly discovered that Cordyceps sinensis was a potent biocatalyst for the biotransformation of ginsenoside Rb1 into CK. After a series of investigations on the biotransformation parameters, an optimal composition of the biotransformation culture was found to be lactose, soybean powder and MgSO₄ without controlling the pH. Also, an optimum temperature of 30 °C for the biotransformation process was suggested in a range of 25 °C-50 °C. Then, a biotransformation pathway of Rb1→Rd→F2→CK was established using high performance liquid chromatography/quadrupole time-of-flight mass spectrometry (HPLC-Q-TOF-MS). Our results demonstrated that the molar bioconversion rate of Rb1 to CK was more than 82% and the purity of CK produced by C. sinensis under the optimized conditions was more than 91%. In conclusion, the combination of C. sinensis and the optimized conditions is applicable for the industrial preparation of CK for medicinal purposes.

Synthesis of isopropyl-1-thio-beta-D-glucopyranoside (IPTGlc), an inducer of Aspergillus niger B1 beta-glucosidase production

Production of beta-glucosidase in Aspergillus niger B1 is subjected to catabolic repression by glucose. Aspergillus niger B1 grown on bran as a carbon source secreted beta-glucosidase. The maximum level of the enzyme was reached after 7 d of fermentation. Addition of 1% glucose to the medium suppressed beta-glucosidase production to undetectable levels. In this study, the organic synthesis of a potential inducer of beta-glucosidase production by A. niger B1's reported. Isopropyl-1-thio-beta-D-glucopyranoside (IPTGlc) was synthesized using a two-step organic synthesis protocol. The H-NMR data agreed with those reported previously for the galactoside analog. When IPTGlc was added 24 h after inoculation at a final concentration of 0.4 mM, similar levels of beta-glucosidase were reached 3 to 4 d earlier as compared to fermentation without IPTGlc induction. In practice, this may translate to a more efficient method of producing beta-glucosidase from this fungus.