Controlled production of fructose by an exoinulinase from Aspergillus ficuum.
An exoinulinase has been isolated, purified and characterised from a commercially available broth of Aspergillus ficuum. The enzyme was purified 4.2-fold in a 21% yield with a specific activity of 12,300 U mg(-1)(protein) after dialysis, ammonium sulphate fractionation and Sephacryl S-200 size exclusion and ion exchange chromatography. The molecular weight of this enzyme was estimated to be 63 kDa by SDS-PAGE. It exhibited a pH and temperature optima of 5.4 and 50 degrees C respectively and under such conditions the enzyme remained stable with 96% and 63.8% residual activity after incubation for 12 h and 72 h respectively. The respective K (m) and V (max) values were 4.75 mM and 833.3 micromol min(-1) ml(-1), respectively. Response surface methodological statistical analysis was evaluated for the maximal production of fructose from the hydrolysis of pure commercial chicory inulin. Incubation of the dialyzed crude exoinulinase (100 U/ml, 48 h, 50 degrees C, 150% inulin, pH 5.0) produced the highest amount of fructose (106.4 mg/ml) under static batch conditions. The purified exoinulinase was evaluated for fructose production and the highest amount (98 mg/ml) was produced after 12 h incubation at 50 degrees C, 150% inulin pH 5.0. The use of a crude exoinulinase preparation is economically desirable and the industrial production of fructose from inulin hydrolysis is biotechnologically feasible.
Mutanda
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Department of Biochemistry, Microbiology and Biotechnology, Rhodes University, Grahamstown, South Africa. taurai7@yahoo.com
Wilhelmi
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Whiteley
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D001230:Aspergillus / Q000201:enzymology*; D003198:Computer Simulation; D004789:Enzyme Activation; D004795:Enzyme Stability; D005632:Fructose / Q000138:chemical synthesis*; D006026:Glycoside Hydrolases / Q000737:chemistry*; D007444:Inulin / Q000737:chemistry*; D008956:Models, Chemical
D005632:Fructose; D007444:Inulin; D006026:Glycoside Hydrolases; C023086:inulinase