Endophytic and Rhizospheric Actinobacteria from Guiera senegalensis as Novel Sources of Glucose Isomerase under Submerged Fermentation

Abstract

Glucose isomerase (GI) is a key industrial enzyme used to convert glucose to fructose in the production of high-fructose corn syrup (HFCS). Despite the widespread application of GI, there is a growing need to explore novel and cost-effective microbial sources, particularly endophytic Actinobacteria, which are known for their metabolic versatility and enzyme-producing capabilities. However, there is no evidence of GI production potential from Actinobacteria associated with Guiera senegalensis. This study aimed to isolate endophytic and rhizospheric Actinobacteria from Guiera senegalensis and evaluate their potential for Glucose isomerase production under submerged fermentation conditions. Endophytic Actinobacteria were isolated from the roots of G. senegalensis obtained from farmland within Abdullahi Fodio University of Science and Technology, Aliero (AFUSTA). GI production was performed via submerged fermentation for 72 hours, with enzymatic activity assessed at 24-hour intervals. The six (6) isolated Actinobacterial strains appeared in different colours (white, yellow, and pale yellow) and textures (filamentous, moist, convex, and fluffy). GI activity was measured by measuring the absorbance of the 2 mL reaction mixture in triplicate. Fructose concentration was determined from a calibration curve prepared using standard fructose solutions (0–100 µg/mL). One unit (U) of glucose isomerase activity was defined as the amount of enzyme required to catalyze the formation of 1 µmol of fructose per minute under the specified assay conditions. The GI activity produced by six (6) isolates was determined to be 5.22±1.03 EU/ml, 4.85±0.54 EU/ml, 5.07±0.33 EU/ml, 5.0±0.78 EU/ml, 4.28±0.65 EU/ml, and 4.92±0.48 EU/ml. Isolate S-1 recorded the highest activity (5.22±1.03EU/ml). The optimal temperature and pH for GI production were determined to be 35 °C and 6, respectively. Kinetic parameters (Km) and Vmax were found to be 2.3202 mM and 39.0625 U/mL, respectively. These findings demonstrate that endophytic Actinobacteria associated with G. senegalensis represent a promising microbial resource for GI production and High Fructose Corn Syrup production, an essential sweetener in the food and beverage industries. Further studies on strain improvement and large-scale production are recommended to enhance its industrial production.