Comparison of action patterns of gelatin-entrapped and surface-bound glucoamylase on an α-amylase degraded starch substrate: a critical examination of reversion products

The action pattern of gelatin-entrapped and surface-bound glucoamylase (exo-1,4-α-d-glucosidase, EC 3.2.1.3) on an α-amylase (1,4-α-d-glucan glucanohydrolase, EC 3.2.1.1) partially hydrolysed starch is reported. Differences have been observed between the action patterns of the two forms of gelatin-immobilized glucoamylase. Both the forward and reverse reactions have been critically examined in depth by sophisticated analysis techniques. The entrapped enzyme favoured the synthesis of (1→6) linked oligosaccharides, mainly isomaltose (9.8%). These reversion products were found in very low concentrations (0.75–1.5%) with gelatin-TiCl₄(liquid) chelate/metal link-coupled enzyme, and no (1→6) linked reversion products were found on gelatin-glutaraldehyde coupled glucoamylase. The level of (1→6) linked reversion products appeared to influence the formal DE value of the d-glucose syrup, being 94.2 and 98.1 for the gelatin-entrapped enzyme and the gelatin-glutaraldehyde surface bound enzyme, respectively. These action patterns and the production of reversion products are discussed in the light of the application of immobilization techniques to the production of high DE d-glucose syrups and the likely failure of systems to achieve 100% conversion.     

Behaviour of Endomycopsis fibuligera glucoamylase towards raw starch

An extracellular glucoamylase [exo-1,4-α-d-glucosidase, 1,4-α-d-glucan glucohydrolase, EC 3.2.1.3] of Endomycopsis fibuligera has been purified and some of its properties studied. It had a very high debranching activity (0.63). The enzyme was completely adsorbed onto raw starch at all the pH values tested (pH 2.0–7.6). Amylase inhibitor from Streptomyces sp. did not prevent the adsorption of glucoamylase onto raw starch although the enzyme did not digest raw starch in the presence of amylase inhibitor. Sodium borate (0.1 m) eluted only 35% of the adsorbed enzyme from raw starch. The optimum pH for raw starch digestion was 4.5 whereas that of boiled soluble starch hydrolysis was 5.5. Waxy starches were more easily digested than non-waxy starches, and root starches were slowly digested by this enzyme.     

Soluble and immobilized enzyme technology in bioconversion of barley starch

Homogeneous and heterogeneous biocatalysis were both investigated as tools for barley starch syrup production. Barley starch was first liquefied by soluble heat-stable Bacillus sp. α-amylase EC 3.2.1.1 (1,4-α-d-glucan glucanohydrolase) Termamyl 60 L at 95°C, pH 6.5, to obtain slurries of varying DE-values up to ≈37. Alternatively, it was extruded with a Creusot-Loire BC 45 twin-screw extruder at 25% moisture, 150°C, for denaturation. After cooling and adjusting the pH to 4.5 or grinding, respectively, the pretreated starch was saccharified either by soluble or by immobilized Aspergillus niger glucoamylase EC 3.2.1.3 (1,4-α-d-glucan glucohydrolase) at 60°C, pH 4.5, to obtain glucose syrup of up to DE 96. The course of hydrolysis was followed by automated Biogel P-2 chromatographic analysis. Glucoamylase was immobilized either on a phenol-formaldehyde resin Duolite S 761 or on silanized Spherosil porous silica beads. Barley glucose syrup obtained was further continuously converted to high fructose syrup by a packed bed reactor of Actinoplanes missouriensis whole cell glucose isomerase (EC 5.3.1.5) Maxazyme entrapped within α-cellulose beads. We could conclude that barley starch may be used as an alternative raw material for biocatalytic starch syrup production.     

Immobilization of enzymes on spheron: 1. Trypsin and glucoamylase by the titanium-chelation method

In a preliminary study, trypsin (EC 3.4.21.4) and glucoamylase (exo-1,4-α-d-glucosidase, 1,4-α-d-glucan glucohydrolase, EC 3.2.1.3) were immobilized on Spheron by the titanium-chelation method. The activity of trypsin immobilized on Spheron P100 000 was higher against tosyl-l-arginine 4-nitroanilide than against casein. The variation in the specific activities of glucoamylase immobilized on Spherons of different porosities to wards substrates of different molecular weights was examined.     

HTST-extrusion cooking in ethanol production from starchy materials

Starch syrup for ethanol fermentation is conventionally produced by acid or enzymatic hydrolysis. Recently, however, promising results have been obtained using HTST-extrusion cooking in starch liquefaction. The starchy material was pregelatinized and preliquefied in a Creusot-Loire BC45 twin-screw HTST-extrusion cooker before simultaneous saccharification by amyloglucosidase and fermentation by Saccharomyces cerevisiae or Zymomonas mobilis. With pretreatment of milled whole grain or starch by HTST-extrusion cooking a significantly shorter fermentation time could be achieved. Maximum ethanol yield was obtained in 45 h using conventional yeast and amyloglucosidase (1,4-α-d-glucan glucohydrolase, EC 3.2.1.3) dosage, even without addition of Termamyl α-amylase (1,4-α-d-glucan glucanohydrolase, EC 3.2.1.1) during thermomechanical liquefaction. Immobilized yeast could also be used to produce ethanol both by a batch or continuous process. In this case, for a continuous process the DE-value of the syrup should be sufficiently high. A model for ethanol production as a function of dry matter, fermentation time, and yeast and Termamyl quantities has been developed.     

Assay of α-amylase in soil and river sediments: Its use to determine the effects of heavy metals on starch degradation

α-Amylase (1,4-α-d-glucan glucanohydrolase EC 3.2.1.1) activity was assayed and characterized in soil and in starch amended river sediment. Zero order reactions between initial activity; length of incubation; soil or sediment weight; and substrate concentration were demonstrated. Optimum pH for α-amylase activity in soil was 5.0 and in sediment 5.9–6.2, while the temperature optima were 37°C and 45°C respectively. The addition of starch to samples of sediment led to a marked increase in α-amylase and numbers of amylolytic bacteria. An example is also given of how the assay can be used to determine the effects of heavy metals on α-amylase activity in a river sediment.     

Complete amino acid sequence and location of the five disulfide bridges in porcine pancreatic α-amylase

Porcine pancreatic α-amylase (1,4-α-d-glucan glucanohydrolase EC 3.2.1.1), a single polypeptide chain, contains nine residues of methionine. Eight different fragments resulting from cleavage of this molecule by cyanogen bromide were characterized. The sequences of six of them have previously been reported. Two missing fragments, CN2 (82 residues) and CN3b1 (76 residues) were purified after breaking of the interpeptidic disulfide bridge and their complete sequence as well as that of the previously purified CN1 peptide (102 residues) are reported here. The location of the three disulfide bridges present in these peptides was determined. Ordering of the carboxymethylated cyanogen bromide fragments was carried out by pulse labeling the amylase chain in vivo. The complete sequence of the porcine pancreatic amylase chain (496 residues) and the location of its five disulfide bridges is presented. Comparison with human and mouse pancreatic and salivary α-amylases and with rat pancreatic amylase obtained from the corresponding cDNA nucleotidic sequences shows a high degree of homology between mammalian α-amylases.     

Immobilization of glucoamylase on porous silicas

The influence of the pore structure of silica carriers (macroporous silica gels, silochromes and porous glasses) on the catalytic activity of immobilized glucoamylase (exo 1,4-α-d-glucosidase, 1,4-α-d-glucan glucohydrolase EC 3.2.1.3) has been studied. The dependence of the immobilized glucoamylase activity, in units g^?1, on the carrier pore diameter was found to pass through a maximum within a range 70–100 nm. Macroporous silica gels can be used with success as carriers for glucoamylase immobilization instead of porous glasses and silochromes.     

Pretreatment of starch raw materials and their enzymatic hydrolysis by immobilized glucoamylase

The pretreatment of starch raw materials such as sweet potato, potato and cassava has been carried out using various types of crusher, viz juice mixer, homogenizer and high-speed planetary mill. The effect of pretreatment of the materials on their enzymatic hydrolysis was studied. High-speed planetary mill treatment was the most effective and comparable with heat treatment (pasting). Various crushing times were used to examine the effect of crushing by mill treatment on the enzymatic hydrolysis. In the enzymatic hydrolysis of cassava, the use of both cellulase [1,4-(1,3; 1,4)-β-d-glucan 4-glucanohydrolase, EC 3.2.1.4] and glucoamylase [1,4-α-d-glucan glucohydrolase, EC 3.2.1.3] enhanced the d-glucose yield. The immobilization of glucoamylase was studied by radiation polymerization of hydrophilic monomers at low temperature, and it was found that enzymatic activity of the immobilized glucoamylase particles varied with monomer concentration and particle size. Starchy raw materials pretreated with the mill can be efficiently hydrolysed by immobilized glucoamylase.     

Fast and reliable method for simultaneous zymographic detection of glucoamylase and α-amylase in fungal fermentation

Detection of α-amylase and glucoamylase in crude fermentation extracts using a single native electrophoresis gel and zymogram is described in this article. Proteins were printed on substrate gel and simultaneously onto a membrane in a three-sandwich gel. α-Amylase was detected on the substrate gel with copolymerized β-limit dextrins and iodine reagent. Glucoamylases were detected on the membrane using a coupled assay for glucose detection. Both amylases were detected in native gel using starch and iodine reagent. The described technique can be a helpful tool for monitoring and control of fermentation processes because fungal amylase producers almost always synthesize both amylases.     

Production of amylases by yeasts

Yeasts (228) isolated for natural habitats were screened for their ability to produce amylases in semisolid medium of wheat bran. Strains of Aureobasidium pullulans, Candida famata, and Candida kefyr showed high enzymatic activity for α-amylase, glucoamylase, and debranching enzyme. Key words: Aureobasidium, Candida, amylolytic yeasts, α-amylase, glucoamylase.     

Proteolytic inactivation of 1, 4-α-d-glucan 6-α-d-glucosyltransferase purified from Aspergillus niger R-27

An extracellular 1,4-α-d-glucan 6-α-d-glucosyltransferase [d-glucosyltransferase, 1,4-α-d-glucan:1,4-α-d-glucan(d-gluco 6-α-d-glucosyltransferase, EC 2.4.1.24] from Aspergillus niger R-27 has been purified and the kinetics of its proteolytic inactivation with subtilisin studied. The purified enzyme was shown to be homogeneous using disc polyacrylamide gel electrophoresis. It contained 16.0% mannose, 0.19% glucose and 2.95% 2-acetamido-2-deoxy-d-glucose. The characteristic feature of the proteolytic degradation of glucosyltransferase is rapid hydrolysis of ～12 peptide bonds per mol and the formation of an active intermediate product which is more resistant to further proteolysis, but is easily heat-inactivated. The isolation and some properties of glucosyltransferase are also described.     

Immobilization of Penicillium funiculosum cellulase on a soluble polymer

The three cellulase [see 1,4-(1,3;1,4)-β-d-glucan 4-glucanohydrolase, EC 3.2.1.4] components of Penicillium funiculosum have been immobilized on a soluble, high molecular weight polymer, poly(vinyl alcohol), using carbodiimide. The immobilized enzyme retained over 90% of cellulase [1,4-(1,3;1,4)-β-d-glucan 4-glucanohydrolase, EC 3.2.1.4], and exo-β-d-glucanase [1,4-β-d-glucan cellobiohydrolase, EC 3.2.1.91] and β-d-glucosidase [β-d-glucoside glucohydrolase, EC 3.2.1.21] activities. The bound enzyme catalysed the hydrolysis of alkali-treated bagasse with a greater efficiency than the free cellulase. The potential for reuse of the immobilized system was studied using membrane filters and the system was found to be active for three cycles.     

Measurement of α-amylase and glucoamylase activities produced during fermentation

A method for the automatic measurement of α-amylase and glucoamylase activities during fermentation has been developed. Soluble starch dyed with Remazol Brilliant Orange was used as the substrate for α-amylase and 4-nitrophenyl α-d-glucopyranoside for glucoamylase. The same automatic analysis system could be used for both of these enzymes because the reaction products were measured at the same wavelength. Simultaneous pick-up of enzyme and the respective substrate was enabled by using two samplers. The presence of α-amylase did not interfere with the glucoamylase determination. Absolute values for α-amylase activity were obtained using a mathematical correction. Monitoring of these enzymes was accomplished during microbial fermentation.     

Preparation,characterization and laboratory-scale application of an immobilized glucoamylase

Glucoamylase (1,4-α-d-glucan glucohydrolase, EC 3.2.1.3) has been covalently immobilized on a polyacrylamide-type support containing carboxylic groups activated by water-soluble carbodiimide. The activity was 5.5– 6.0 units g^?1solid. The optimum pH for catalytic activity was pH 3.8. The apparent optimum temperature was found at 60°C. With soluble starch as substrate the K_m value was 14 mg ml^?1. The pH for maximum stability was pH 4.0–4.5. In the presence of 8 m urea the immobilized glucoamylase retained most of its catalytic activity but it was more susceptible to guanidinium hydrochloride than the soluble enzyme. The practical applicability of immobilized glucoamylase was tested in batch process and continuous operation.     

Immobilization of enzymes on Spheron: 2. β-Amylase — The development of a column reactor—separator

The titanium-chelation method has been used to immobilize β-amylase (1,4-α-d-glucan maltohydrolase, EC 3.2.1.2) on to Spheron. On various grades of Spheron, protein coupling yields of 56–76% were obtained with barley and sweet-potato β-amylases. The specific enzymic activities of the immobilized enzymes fell in the range 3.7–7.6% of those of the soluble enzymes. The immobilized enzymes were more stable than the soluble, especially in the presence of l-cysteine and serum albumin. The presence of cysteine and serum albumin brought about increases in activity in the preparations, presumably by regenerating essential thiol groups in the enzyme which had been oxidized during the operations. Maltose could be separated from amylopectin and other large polysaccharides by chromatography on Spheron P100, and a system was developed in which maltose, produced by hydrolysis of amylopectin applied in pulses to a column of immobilized β-amylase, was separated from starting material and by-products on a second column of Spheron P100.     

Growth and amylolytic activity of Aureobasidium pullulans in starch-limited culture

One strain of the yeast-like fungus Aureobasidium pullulans has been found which converts starch into biomass with a high yield (Y_starch = 0.590) and releases glucoamylase (1,4-α-d-glucan glucohydrolase EC 3.2.1.3) to a certain extent (ca. 2.2–2.3 U ml^?1) into the culture medium. The rate of starch hydrolysis seems to be high enough so as not to limit the specific growth rate.     

Immobilization of glucoamylase from Aspergillus niger on poly(ethylenimine)-coated non-porous glass beads

Glucoamylase (1,4-α-d-glucan glucohydrolase, EC 3.2.1.3) from A. niger was immobilized on cationic nonporous glass beads (13–44 μm) by electrostatic adsorption followed by rosslinking with glutaraldehyde. Over 80% of the enzyme's total soluble activity was expressed upon immobilization. d-Glucose production from maltodextrins was virtually complete, suggesting that the lack of pores can eliminate the problem of product reversion. Immobilized glucoamylase showed decreased stability upon heating, compared with the soluble enzyme.     

Maltose-forming α-amylase from the hyperthermophilic archaeon Pyrococcus sp. ST04

The deduced amino acid sequence from a gene of the hyperthermophilic archaeon Pyrococcus sp. ST04 (Py04_0872) contained a conserved glycoside hydrolase family 57 (GH57) motif, but showed <13 % sequence identity with other known Pyrococcus GH57 enzymes, such as 4-α-glucanotransferase (EC 2.4.1.25), amylopullulanase (EC 3.2.1.41), and branching enzyme (EC 2.4.1.18). This gene was cloned and expressed in Escherichia coli, and the recombinant product (P yrococcus sp. ST04 maltose-forming α-amylase, PSMA) was a novel 70-kDa maltose-forming α-amylase. PSMA only recognized maltose (G2) units with α-1,4 and α-1,6 linkages in polysaccharides (e.g., starch, amylopectin, and glycogen) and hydrolyzed pullulan very poorly. G2 was the primary end product of hydrolysis. Branched cyclodextrin (CD) was only hydrolyzed along its branched maltooligosaccharides. 6-O-glucosyl-β-cyclodextrin (G1-β-CD) and β-cyclodextrin (β-CD) were resistant to PSMA suggesting that PSMA is an exo-type glucan hydrolase with α-1,4- and α-1,6-glucan hydrolytic activities. The half-saturation value (K _m) for the α-1,4 linkage of maltotriose (G3) was 8.4 mM while that of the α-1,6 linkage of 6-O-maltosyl-β-cyclodextrin (G2-β-CD) was 0.3 mM. The k _cat values were 381.0 min^?1 for G3 and 1,545.0 min^?1 for G2-β-CD. The enzyme was inhibited competitively by the reaction product G2, and the K _i constant was 0.7 mM. PSMA bridges the gap between amylases that hydrolyze larger maltodextrins and α-glucosidase that feeds G2 into glycolysis by hydrolyzing smaller glucans into G2 units.     

Purification and properties of two exo-cellobiohydrolases from a cellulolytic culture of Fusarium lini

Two distinct exo-cellobiohydrolases (1,4-β-d-glucan cellobiohydrolase, EC 3.2.1.91) have been isolated from culture filtrates of Fusarium lini by repeated ammonium sulphate fractionation and isoelectric focusing. The purified enzymes were evaluated for physical properties, kinetics and the mechanism of their action. The results of this work were as follows. (1) A two-step enzyme purification procedure was developed, involving isoelectric focusing and ammonium sulphate fractionation. (2) Yields of pure cellobiohydrolases I and II were 45 and 36 mg l^?1 of culture broth, respectively. (3) Both enzymes were found to be homogeneous, as determined by ultracentrifugation, isoelectric focusing, electrophoresis in polyacrylamide gels containing SDS and chromatography on Sephadex. (4) The molecular weights of the two cellobiohydrolases, as determined by gel filtration and SDS gel electrophoresis, were 50 000–57 000. (5) Both cellobiohydrolases had low viscosity-reducing and reducing sugar activity from carboxymethyl cellulose and high activity with Walseth cellulose and Avicel. (6) The enzymes produced only cellobiose as the end product from filter paper and Avicel, indicating that they are true cellobiohydrolases. (7) Cellobiohydrolase I hydrolysed d-xylan whereas cellobiohydrolase II was inactive towards d-xylan. (8) There was a striking synergism in filter paper activity when cellobiohydrolase was supplemented with endo-1,4-β-d-glucanase [cellulase, 1,4-(1,3;1,4)-β-d-glucan 4-glucanohydrolase, EC 3.2.1.4] and β-d-glucosidase (β-d-glucoside glucohydrolase, EC 3.2.1.21).