Glucose(xylose) isomerase production by Streptomyces sp. CH7 grown on agricultural residues

Production, purification and physicochemical characterization of D-xylose/glucose isomerase from Escherichia coli strain BL21

Cell lysate of Escherichia coli strain BL21 showed significant D-glucose isomerase activity. The rate of glucose conversion was increased up to 40% when cells were induced with 1% D-xylose. E. coli BL21 xylose isomerase (ECXI-BL21) was purified to homogeneity, up to 1.9-fold with overall 10.88% enzyme yield by heat shock, salting out and electro-elution. The molecular mass of ECXI-BL21 was estimated as 43.9 kDa on SDS-PAGE. pH_opt. and T_opt. of the enzyme were calculated as 7.0 and 50 °C, respectively. Activation energy (E _a) of ECXI-BL21 was 45 kJ/mol. Enzyme was stable from 30 to 55 °C and at pH range 6.0-8.0. ECXI-BL21_(holo) was activated by 10 mM magnesium (35%), 0.5 mM cobalt (20%) and manganese (25%), and 0.5/10 mM Mn²⁺/Mg²⁺ (50%) and Co²⁺/Mg²⁺ (30%) as compared to ECXI-BL21_(apo). Catalytic affinity (K _m) of ECXI-BL21 for D-glucose was calculated as 0.82 mM, while maximum velocity (V _max) of the reaction D-glucose_(aldo) ⇌ D-fructose_(keto) was 108 μmol/mg/min. D-fructose formed was identified on silica gel plate. This thermophilic enzyme, T _m = 75 °C, has great potential for high fructose syrup production used in food and soft drink industries.

Purification and kinetic behavior of glucose isomerase from Streptomyces lividans RSU26

Glucose isomerase (GI), an enzyme with deserved high potential in the world market. GI plays a major role in high Fructose Corn Syrup Production (HFCS). HFCS is used as a sweetener in food and pharmaceutical industries. Streptomyces are well-known producers of various industrially valuable enzymes, including Glucose isomerase. Currently, recombinant strains have been available for the production of various enzymes, but it has limitation in the large scale production. Therefore, identifying effective streptomyces strains have emerged. The current study, the novel S. lividans RSU26 was isolated from a marine source and optimized its potential to produce glucose isomerase at different physical and chemical conditions. The optimum pH and temperature for GI and biomass production were 7.5 and 35 °C, respectively at 96 h. Characterization study revealed that the approximate molar mass of GI was 43 kDa for monomeric and 170 kDa for tetrameric forms. Kinetic behavior exhibits Km, and Vmax values for the conversion of fructose to glucose conversion were 48.8 mM and 2.54 U mg⁻¹ at 50 °C and glucose to fructose were 29.4 mM and 2.38 U mg⁻¹ at 65 °C protein, respectively. Therefore, the present study suggested that the wild–type S. lividans RSU26 has strong potential to produce glucose isomerase for various industrial applications.