Abstract
The present study first identified the biotransformation of starch as a novel preparation method was investigated using the alpha-transglucosidase-producing Geobacillus stearothermophilus U2. Subsequently, 5 L- and 20 L-scale fermentations were performed. After isolation and purification, liquid alpha-glucosidase preparations were obtained. Through covalent cross-linking and adsorption cross-linking using chitosan as the carrier and glutaraldehyde as the crosslinking agent, the conditions for immobilization of alpha-glucosidase on chitosan were determined. Moreover, Isomaltooligosaccharides (IMOs) were then prepared using chitosan membrane-immobilized alpha-glucosidase, beta-amylase, pullulanase, fungal alpha-amylase and starch as substrate. The mixed syrup that contained IMOs was evaluated and analyzed by thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC). In addition, small-scale preparation of IMOs was performed. These results are a strong indication that the alpha-transglucosidase-producing G. stearothermophilus as a potential application technique can be successfully used to prepare industrial IMOs.
Highlights
Alpha-glucosidases (EC3.2.1.20) belong to the starch hydrolase family and mainly exert their functions outside of cells (Hirschhorn, Huie & Kasper, 2002)
Based on the above experimental results, starch, peptone, beef extract, yeast powder, MgCl2 and K2HPO4 were selected as the components of the optimized fermentation medium
The optimized the conditions for biotransformation of starch into isomaltooligosaccharides using thermostable alpha-glucosidase from G. stearothermophilus U2 has been investigated
Summary
Alpha-glucosidases (EC3.2.1.20) belong to the starch hydrolase family and mainly exert their functions outside of cells (Hirschhorn, Huie & Kasper, 2002). Alpha-glucosidase hydrolyzes the alpha-glycosidic bond from the non-reducing end of the polysaccharide substrate, releasing alpha-D-glucose. Alpha-glucosidases are generally categorized as hydrolytic enzymes (class 3) and mainly hydrolyze disaccharides, oligosaccharides, aromatic glycosides, sucrose and polysaccharides (Mohamed Sham Shihabudeen, Hansi Priscilla & Thirumurugan, 2011; Verastegui-Omaña et al, 2017). In the starch and sugar industry, alpha-glucosidase is mainly used, together with alpha-amylase, in the production of high-glucose syrup
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