Symmetric enzyme distribution in asymmetric UF polysulfone membranes

Invertase as well as as amyloglucosidase were immobilized within asymmetyric ultrafiltration membranes that were prepared from polysulfone or homogeneously modified polysulfone. The chemical modification was carried out by sulfonation and halomethylation. This additional change of the surface properties of the capillaries within the membrane offers the possibilities for various types of enzyme fixation, namely adsorption, charge interactions, or covalent bonding. By variation of the immobilization conditions the distribution of the enzyme could be adjusted over the membrane's cross section. At a distinct enzyme concentration in the loading solution a homogeneous enzyme distribution within the membrane could be verified. This was shown by diffusion experiments. Under ultrafiltration conditions using a solution that contains membrane-impermeable macromolecules as well as a membrane-permeable solute like saccharose the residence time within the membrane was increased due to gel formation atop the membrane yet the kinetic was no affected. The nonpermeable soluble starch was not reacted by the amyloglucosidase membrane, indicating that the skin layer was free of enzymes. (c) 1994 John Wiley & Sons, Inc.     

Glucose measurement errors in enzymic starch hydrolysates at high enzyme-glucose weight ratios

The 3,5-dinitrosalicylic acid (DNS), o -toluidine, and glucose oxidase methods accurately measured concentrations of standard glucose solutions in the absence of the starch hydrolyzing enzymes Diazyme (amyloglucosidase) and Clarase (α-amylase). In the presence of high enzyme concentrations, particularly at low glucose concentrations, glucose oxidase and o -toluidine somewhat underestimated standard glucose concentrations while DNS overestimated the glucose concentration by 100%. DNS also overestimated glucose in hydrolysates of standard potato starch. Glucose recovery was estimated at almost 200% of that given by glucose oxidase when enzyme starch weight ratios were 9:1 or more. Glucose was underestimated by o -toluidine in starch hydrolysates in the presence of Diazyme at high enzyme-starch weight ratios. DNS similarly overestimated glucose in starch hydrolysates from white spruce ( Picea glauca (Moench.) Voss) and some other species, as enzyme-starch weight ratios increased. The o -toluidine and glucose oxidase reactions were more reliable. Overestimation of the DNS reaction was not improved by treating the glucose-enzyme solutions with anion or cation exchange resins or by removing the enzyme prior to measurement.     

Purification of amyloglucosidase

Amyloglucosidase (glucoamylase; EC 3.2.1.3) has been purified from the culture filtrates of Aspergillus candidus Link var. aureus using hydrophobic interaction chromatography and DEAE-cellulose treatment. The enzyme thus obtained has a specific activity of 329 units/mg protein with the overall recoveries between 70 and 75%. The process appears to be of industrial promise.     

Evidence of native starch degradation with human small intestinal maltase-glucoamylase (recombinant)

Action of human small intestinal brush border carbohydrate digesting enzymes is thought to involve only final hydrolysis reactions of oligosaccharides to monosaccharides. In vitro starch digestibility assays use fungal amyloglucosidase to provide this function. In this study, recombinant N-terminal subunit enzyme of human small intestinal maltase-glucoamylase (rhMGAM-N) was used to explore digestion of native starches from different botanical sources. The susceptibilities to enzyme hydrolysis varied among the starches. The rate and extent of hydrolysis of amylomaize-5 and amylomaize-7 into glucose were greater than for other starches. Such was not observed with fungal amyloglucosidase or pancreatic alpha-amylase. The degradation of native starch granules showed a surface furrowed pattern in random, radial, or tree-like arrangements that differed substantially from the erosion patterns of amyloglucosidase or alpha-amylase. The evidence of raw starch granule degradation with rhMGAM-N indicates that pancreatic alpha-amylase hydrolysis is not a requirement for native starch digestion in the human small intestine.     

Synthesis of Guaiacol-α-D-glucoside and Curcumin-bis-α-D-glucoside by an Amyloglucosidase from Rhizopus

Guaiacol (2-methoxyphenol) and curcumin [1E,6E-1,7-di(4-hydroxy-3-methoxy-phenyl)-1,6-heptadiene-3,5-dione] were converted into their corresponding glucosides using glucose and an amyloglucosidase from Rhizopus. Guaiacol-α-D-glucoside yields ranged from 3 to 52% with the highest at pH 7.0. Curcumin-bis-α-D-glucoside yields ranged from 3 to 48% with the highest at pH 4.0 with 50% (w/w D-glucose) of enzyme. The phenolic hydroxyl group of guaiacol and both phenolic hydroxyl groups of curcumin were glucosylated at the C1 carbon of α-D-glucose indicating that the enzymatic reaction is stereospecific. Both guaiacol-α-D-glucoside and curcumin-bis-α-D-glucosides had antioxidant activities.     

Degradation of starchy substrates by a crude enzyme preparation and utilization of the hydrolysates for lactic fermentation

An enzyme preparation obtained from Aspergillus ustus, possessing cellulase, α-amylase, amyloglucosidase, proteinase and d-xylanase activities, was used along with commercial bacterial α-amylase and amyloglucosidase for the degradation of ragi (Eleusine coracana) flour and wheat (Triticum vulgare) bran. Lactic acid yield from ragi hydrolysate, adjusted to 5% reducing sugars (w/v), was 25% when fermented with Lactobacillus plantarum. The yields increased to 78% and 94% when the ragi hydrolysate was fortified with 20% and 60% (v/v) wheat bran hydrolysate, respectively. When commercial α-amylase and amyloglucosidase were used for the hydrolysis of ragi and wheat bran and L. plantarum was employed to ferment the hydrolysates containing 5% reducing sugars (w/v), lactic acid yields were 10% in ragi hydrolysate and 57% and 90% when the ragi hydrolysate was fortified with 20% and 60% (v/v) of wheat bran hydrolysate, respectively. α-Amylase and amyloglucosidase hydrolysed wheat bran added at 20% (v/v) as the sole source of nutrient to soluble starch hydrolysate (5% reducing sugars) gave 22% yield of lactic acid. The yield increased to 55% by the utilization of A. ustus enzyme preparation in addition to α-amylase and amyloglucosidase for wheat bran hydrolysis.     

多孔醋酸纤维素球形载体固定化糖化酶的研究

报道了一种多孔醋酸纤维素球形固定化酶载体的制备技术,以NaIO₄氧化法活化,固定糖化酶,测定了固定化糖化酶的催化反应特性,并与游离酶作了比较.固定化酶在55℃下水解10批淀粉溶液,总反应时间超过24 h,活力无显著变化.     

Production of raw-starch digesting amyloglucosidase by Aspergillussp GP-21 in solid state fermentation

Aspergillus sp GP-21 produced a raw-starch digesting amyloglucosidase which showed optimum activity at 65°C and pH 5.0–5.5. At 50°C the enzyme converted about 40% of raw corn starch to glucose within 48 h. Enzyme production was studied in solid state fermentation using wheat bran. Productivity was affected by the level of moisture, incubation temperature and the presence or absence of supplements. Maximum enzyme production was observed at a moisture level of 75% and at 30°C. Enzyme production was stimulated by supplementing wheat bran with 0.25% proteose peptone, 1% trace mineral solution, 0.01% CaCl₂ and 0.01% MgSO₄. Received 27 October 1998/ Accepted in revised form 15 March 1999     

New and effective entrapment of polyelectrolyte-enzyme-complexes in LentiKats

Amyloglucosidase EC 3.2.1.3 was used as model for the immobilisation of enzymes in poly(vinylalcohol) hydrogel (LentiKats) lenses. The entrapment of the enzyme in PVA-hydrogel based on a two-step procedure, firstly its coupling to polyelectrolytes increased the structure level of the enzyme, and subsequently, the resulting complex was entrapped in LentiKats. The immobilised enzyme retained 45% of its original activity and lost no activity over five repeated batch runs.