The production of Exo- and Endo- β- Glucan from Malaysian Ganoderma lucidum in a repeated batch fermentation and its role as α-Glucosidase inhibitor

Abstract

Polysaccharides extracted from Ganoderma lucidum (GL) were reported previously as promising anti-diabetic drugs. They have shown inhibition of glucosidase enzyme, one of the primary targets for type 2 diabetes mellitus (T2DM) treatment. This study aims to identify the roles of EPS and ENS extracted from GL in inhibiting the α-glucosidase enzyme. Upscale production of GL was done using a 10L bioreactor. The zebrafish embryo toxicity test was carried out based on OECD guidelines. For diabetes induction, the adult zebrafish (3–4 months of age) were overfed and induced with three doses of 350 mg/kg streptozotocin (STZ) by intraperitoneal injection (IP) on three different days (Day 1, 3, and 5). Oral sucrose tolerance test (OSTT) and anti-diabetic activity of exo-β-glucan (EPS-BG) and endo-β-glucan (ENS-BG) were evaluated (Day 7) using the developed model (n = 15). This study showed both EPS-BG (IC50 = 0.1575 mg/mL) and ENS-BG (IC50 = 0.3479 mg/mL) demonstrated a strong inhibition towards α-glucosidase activity similar to the clinically approved α-glucosidase inhibitor, acarbose (IC50 = 0.8107 mg/mL). ENS is non-toxic towards zebrafish embryos with LC50 of 0.92 mg/mL and showed no significant changes in zebrafish embryo hatching and normal heart rate as compared to untreated embryos (161 beats/min). Teratogenic effects of ENS (<1.0 mg/mL) on zebrafish embryonic development were not observed. The DM model of zebrafish were acquired after the third dose of STZ with a fasting BGL of 8.98 ± 0.28 mmol/L compared to the normal healthy group (4.23 ± 0.62 mmol/L). The BGL of DM zebrafish after 30 minutes treated with EPS-BG and ENS-BG showed a significant reduction. Both EPS-BG and ENS-BG significantly reduced DM zebrafish's peak blood glucose and area under the curve in OSTT. Hence, from the study, GL mycelial pellets withstood seven cycles of long fermentation conditions and possessed anti-diabetic properties, which suits large-scale natural drug fermentation. EPS-BG and ENS-BG extracted from GL showed promising inhibition of the α-glucosidase enzyme and are considered non-toxic in ZE. Moreover, EPS-BG and ENS-BG reduced blood glucose levels and inhibited hyperglycaemia in DM zebrafish.