title: Production of ascorbic acid glucoside by alginate-entrapped mycelia of Aspergillus niger.
abstract: The mycelia of Aspergillus niger, cultivated in a medium containing 45 g l(-1) maltose, 66 g l(-1) yeast extract, and 5 g l(-1) K(2)HPO(4) at 30 degrees C and 200 rpm, were used as a biocatalyst in the glucosylation of ascorbic acid. Free mycelia from 3-day-old culture, when used in a 6-h reaction with maltose as the acyl donor, gave 16.07 g l(-1) ascorbic acid glucoside corresponding to a volumetric productivity of 2.68 g l(-1) h(-1) and a conversion of 67%. Mycelia from 3-day-old cultures were entrapped in calcium alginate beads and used as a catalyst in the glucosylation of ascorbic acid. An ascorbic acid-to-maltose molar ratio of 1:9 was found to be optimum, and the conversion reached 75% after 12 h. The concentration of ascorbic acid glucoside produced at this molar ratio was 17.95 g l(-1), and the productivity was 1.5 g l(-1) h(-1). The biocatalyst was repeatedly used in a fixed bed bioreactor for the synthesis of ascorbic acid glucoside and approximately 17 g l(-1) of ascorbic acid glucoside corresponding to a volumetric productivity of 1.42 g l(-1) h(-1) was produced in each use. The conversion was retained at 70% in each use. The entrapped mycelia also exhibited exceptionally high reusability and storage stability. The product was purified to 85% by anion exchange and gel permeation chromatography with a final yield of 75%.
authors.affiliation: Department of Chemical Engineering, National Tsing Hua University, Hsinchu, Taiwan.
authors.forename: Hsin-Ju
authors.initials: HJ
authors.lastname: Hsieh
authors.forename: Kai-Yu
authors.initials: KY
authors.lastname: Tung
authors.forename: Giridhar R
authors.initials: GR
authors.lastname: Nair
authors.forename: I-Ming
authors.initials: IM
authors.lastname: Chu
authors.forename: Wen-Teng
authors.initials: WT
authors.lastname: Wu
mesh_terms: D000464:Alginates / Q000737:chemistry; D001205:Ascorbic Acid / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D001234:Aspergillus niger / Q000737:chemistry / Q000378:metabolism*; D019149:Bioreactors / Q000382:microbiology; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D005960:Glucosides / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D020723:Glucuronic Acid / Q000737:chemistry; D006031:Glycosylation; D006603:Hexuronic Acids / Q000737:chemistry; D025282:Mycelium / Q000737:chemistry / Q000378:metabolism*; D013696:Temperature
chemical_list: D000464:Alginates; D005960:Glucosides; D006603:Hexuronic Acids; D020723:Glucuronic Acid; D001205:Ascorbic Acid