Production, purification and immobilization of inulinases from Aspergillius species

Abstract

Inulinases are enzymes catalysing hydrolysis of polyfructosans to produce fructose or fructooligosaccharides; these properties have attracted interest of many researchers towards exploring various plant sources (agro food waste) as substrates. According to the literature, various microorganisms, such as fungi, yeast, bacteria, and actinomycetes, can synthesize inulinase. Producer microorganisms can be the micromycetes Aspergillus, Penicillium, Rhizopus and Fusarium, the yeast Kluyveromyces and the bacteria Clostridium thermosuccinogenes and Bacillus subtilis, using inulin, sucrose, fructose, lactose, raffinose, xylose as sources of carbon. The present study mainly envisages inulinase produced by Aspergillius species grown on a fermentation medium based on different carbon sources (inulin and agro-alimentary by-products). The crude extract was purified by fractional precipitation with ammonium sulphate. The dissolved and dialyzed precipitate was further purified by ion exchange chromatography on DEAE-Sephadex. The experiments led to the obtaining of an inulinase with a specific activity of 43.34 U/mg proteins. Inulinase immobilization tests on chitosan beads have led to a stable biocatalyst at temperature and pH variations that could be useful for obtaining fructose syrup.