Purification and properties of a thermophilic amyloglucosidase from Aspergillus niger

Evaluation of extruded starch foam for glucose-supplying biomaterials

The survival rate of mesenchymal stem cells (MSC), a crucial factor in tissue engineering, is highly dependent on glucose supply. The purpose of this paper is to study the potential of starch foams as glucose suppliers. It is investigated through in vitro hydrolysis by amyloglucosidase in conditions that respect physiological constraints (37 °C and pH 7.4), including a duration of 21 days, and no stirring. Nine extruded starch foams with amylose contents ranging from 0 to 74 %, with various cell wall thicknesses (50 to 300 μm), and different crystallinities (0-30 %) were hydrolysed. These kinetics were fitted by a model which shows that the maximum rate of hydrolysis varies from 7 to 100 %, and which allows the rate of hydrolysis at 21 days to be calculated precisely. The results reveal the major role of amylose in glucose delivery kinetics, and the secondary roles of crystallinity and cell wall thickness of the foams. Additional hydrolysis of starch films revealed that thickness positively influences the amylose chain reorganisation during hydrolysis, which, in slows down and limits glucose delivery. A simple glucose delivery kinetics analysis procedure is proposed to select samples for testing as MSC glucose suppliers.

Identification, molecular and biochemical characterization of a novel thermoactive and thermostable glucoamylase from Thermoanaerobacter ethanolicus

PURPOSE

We identified a new glucoamylase (TeGA) from Thermoanaerobacter ethanolicus, a thermophilic anaerobic bacterium. Structural studies suggest that TeGA belongs to the family 15 of glycosylhydrolases (GH15).

METHODS

The expression of this enzyme was optimized in E. coli (BL21) cells in order to have the highest amount of soluble protein (around 3 mg/l of culture medium).

RESULTS

TeGA showed a high optimum temperature of 75 °C. It also showed one of the highest specific activities reported for a bacterial glucoamylase (75.3 U/mg) and was also stable in a wide pH range (3.0-10.0). Although the enzyme was preferentially active with maltose, it was also able to hydrolyze different soluble starches such as those from potato, corn or rice. TeGA showed a high thermostability up to around 70 °C, which was increased in the presence of PEG8000, and also showed to be stable in the presence of moderate concentrations of ethanol.

CONCLUSION

We propose that TeGA could be suitable for use in different industrial processes such as biofuel production and food processing.

A Universal Multichannel Platform for Assembling Enzyme-Based Boolean Logic Gates

Concatenated enzyme-based Boolean logic gates activated with 5 chemical input signals were analyzed with a smartphone photo camera. Simultaneous detection of 32 input combinations was conveniently performed using enzyme-modified fiberglass sensing spots generating fluorescence with different intensities for the 0 and 1 binary outputs. The developed technology offers an easy readout method for multi-channel logic systems.

New insights suggest isomaltooligosaccharides are slowly digestible carbohydrates, rather than dietary fibers, at constitutive mammalian α-glucosidase levels

Isomaltooligosaccharides (IMOs) have been characterized as dietary fibers that resist digestion in the small intestine; however, previous studies suggested that various α-glycosidic linkages in IMOs were hydrolyzed by mammalian α-glucosidases. This study investigated the hydrolysis of IMOs by small intestinal α-glucosidases from rat and human recombinant sucrase-isomaltase complex compared to commonly used fungal amyloglucosidase (AMG) in vitro. Interestingly, mammalian α-glucosidases fully hydrolyzed various IMOs to glucose at a slow rate compared with linear maltooligosaccharides, whereas AMG could not fully hydrolyze IMOs because of its very low hydrolytic activity on α-1,6 linkages. This suggests that IMOs have been misjudged as prebiotic ingredients that bypass the small intestine due to the nature of the assay used. Instead, IMOs can be applied in the food industry as slowly digestible materials to regulate the glycemic response and energy delivery in the mammalian digestive system, rather than as dietary fibers.

Effect of Barium Addition on Hydrolytic Enzymatic Activities in Food Waste Degradation under Anaerobic Conditions

Enzymatic hydrolysis of complex components of residual materials, such as food waste, is a rate-limiting step that conditionates the production rate of biofuels. Research into the anaerobic degradation of cellulose and starch, which are abundant components in organic waste, could contribute to optimize biofuels production processes. In this work, a lab-scale anaerobic semi-continuous hydrolytic reactor was operated for 171 days using food waste as feedstock; the effect of Ba2+ dosage over the activity of five hydrolytic enzymes was also evaluated. No significant effects were observed on the global performance of the hydrolytic process during the steady-state of the operation of the reactor, nevertheless, it was detected that Ba2+ promoted β-amylases activity by 76%, inhibited endoglucanases and α-amylases activity by 39 and 20%, respectively, and had no effect on β-glucosidases and glucoamylases activity. The mechanisms that rule the observed enzymatic activity changes remain unknown; however, the discussion in this paper provides hypothetical explanations for further research.

Purification and biochemical characterisation of glucoamylase from a newly isolated Aspergillus niger: relation to starch processing

Herein, we investigate a glucoamylase from newly isolated Aspergillus niger. The enzyme was purified, using fractionation, followed by anion-exchange chromatography and then characterised. The molecular mass of the enzyme was estimated to be ∼62,000Da, using SDS-PAGE and 57151Da, based on mass spectrometry results. The pI of the protein, and optimum pH/temperature of enzyme activity were 4.4, 5 and 70°C, respectively and the kinetic parameters (Km, Vmax and kcat) were determined to be 0.33 (mgml(-1)), 0.095 (Uμg(-1)min(-1)) and 158.3 (s(-1)) for soluble starch, respectively. The glucoamylase nature of the enzyme was also confirmed using TLC and a specific substrate. Metal ions Fe(3+), Al(3+) and Hg(2+) had the highest inhibitory effect, while Ag(2)(+), Ca(2+), Zn(2+), Mg(2+) and Cd(2+) and EDTA showed no significant effect on the enzyme activity. In addition, thermal stability of the enzyme increased in the presence of starch and calcium ion. Based on the results, the purified glucoamylase appeared to be a newly isolated enzyme.

Enzymatic conversions of starch

This article surveys methods for the enzymatic conversion of starch, involving hydrolases and nonhydrolyzing enzymes, as well as the role of microorganisms producing such enzymes. The sources of the most common enzymes are listed. These starch conversions are also presented in relation to their applications in the food, pharmaceutical, pulp, textile, and other branches of industry. Some sections are devoted to the fermentation of starch to ethanol and other products, and to the production of cyclodextrins, along with the properties of these products. Light is also shed on the enzymes involved in the digestion of starch in human and animal organisms. Enzymatic processes acting on starch are useful in structural studies of the substrates and in understanding the characteristics of digesting enzymes. One section presents the application of enzymes to these problems. The information that is included covers the period from the early 19th century up to 2009.

Cloning, expression, and characterization of a thermostable glucoamylase from Thermoanaerobacter tengcongensis MB4

A thermostable glucoamylase (TtcGA) from Thermoanaerobacter tengcongensis MB4 was successfully expressed in Escherichia coli. The full-length gene (2112 bp) encodes a 703-amino acid polypeptide including a predicted signal peptide of 21 residues. The recombinant mature protein was partially purified to 30-fold homogeneity by heat treatment and gel filtration chromatography. The mature protein is a monomer with the molecular weight of 77 kD. The recombinant enzyme showed maximum activity at 75 degrees C and pH 5.0. It is the most thermostable bacterial glucoamylase described to date with nearly no activity loss after incubation at 75 degrees C for 6 h. TtcGA can hydrolyze both alpha-1, 4- and alpha-1, 6-glycosidic linkages in various alpha-glucans. It showed preference for maltooligosaccharides over polysaccharides with specific activity of 80 U/mg towards maltose. Kinetic studies revealed that TtcGA had the highest activity on maltooligosaccharide with four monosaccharide units. The cations Ca2+, Mn2+, Co2+, Mg2+, and reducing agent DTT showed no obvious effects on the action of TtcGA. In contrast, the enzyme was inactivated by Zn2+, Pb2+, Cu2+, and EDTA.

Characterization of Active Lentinula edodes Glucoamylase Expressed and Secreted by Saccharomyces cerevisiae

The gene encoding Lentinula edodes glucoamylase (GLA) was cloned into Saccharomyces cerevisiae, expressed constitutively and secreted in an active form. The enzyme was purified to homogeneity by (NH4)2SO4 fractionation, anion exchange and affinity chromatography. The protein had a correct N-terminal sequence of WAQSSVIDAYVAS, indicating that the signal peptide was efficiently cleaved. The recombinant enzyme was glycosylated with a 2.4% carbohydrate content. It had a pH optimum of 4.6 and a pH 3.4-6.4 stability range. The temperature optimum was 50 degrees C with stability <or=50 degrees C. The enzyme showed considerable loss of activity when incubated with glucose (44%), glucosamine (68%), galactose (22%), and xylose (64%). The addition of Mn++ activated the enzyme by 45%, while Li+, Zn++, Mg++, Cu+, Ca++, and EDTA had no effect. The enzyme hydrolyzed amylopectin at rates 1.5 and 8.0 times that of soluble starch and amylose, respectively. Soluble starch was hydrolyzed 16 and 29 times faster than wheat and corn starch granules, respectively, with the hydrolysis of starch granules using 10x the amount of GLA. Apparent Km and Vmax for soluble starch were estimated to be 3.0 mg/ml and 0.13 mg/ml/min (40 degrees C, pH 5.3), with an apparent kcat of 2.9 x 10(5) min(-1).

Anaerobic fermentation of gelatinized sago starch-derived sugars to acetone-1-butanol-ethanol solvent by Clostridium acetobutylicum

A study of the kinetics and performance of solvent-yielding batch fermentation of individual sugars and their mixture derived from enzymic hydrolysis of sago starch by Clostridium acetobutylicum showed that the use of 30 g/L gelatinized sago starch as the sole carbon source produced 11.2 g/L total solvent, i.e. 1.5-2 times more than with pure maltose or glucose used as carbon sources. Enzymic pretreatment of gelatinized sago starch yielding maltose and glucose hydrolyzates prior to the fermentation did not improve solvent production as compared to direct fermentation of gelatinized sago starch. The solvent yield of direct gelatinized sago starch fermentation depended on the activity and stability of amylolytic enzymes produced during the fermentation. The pH optima for alpha-amylase and glucoamylase were found to be at 5.3 and 4.0-4.4, respectively. alpha-Amylase showed a broad pH stability profile, retaining more than 80% of its maximum activity at pH 3.0-8.0 after a 1-d incubation at 37 degrees C. Since C. acetobutylicum alpha-amylase has a high activity and stability at low pH, this strain can potentially be employed in a one-step direct solvent-yielding fermentation of sago starch. However, the C. acetobutylicum glucoamylase was only stable at pH 4-5, maintaining more than 90% of its maximum activity after a 1-d incubation at 37 degrees C.

Purification and Properties of a Thermoactive Glucoamylase from Clostridium thermosaccharolyticum

A bacterial glucoamylase was purified from the anaerobic thermophilic bacterium Clostridium thermosaccharolyticum and characterized. The enzyme, which was purified 63-fold, with a yield of 36%, consisted of a single subunit with an apparent molecular mass of 75 kDa. The purified enzyme was able to attack α-1,4- and α-1,6-glycosidic linkages in various α-glucans, liberating glucose with a β-anomeric configuration. The purified glucoamylase, which was optimally active at 70°C and pH 5.0, attacked preferentially polysaccharides such as starch, glycogen, amylopectin, and maltodextrin. The velocity of oligosaccharide hydrolysis decreased with a decrease in the size of the substrate. The K m values for starch and maltose were 18 mg/ml and 20 mM, respectively. Enzyme activity was not significantly influenced by Ca 2+ , EDTA, or α- or β-cyclodextrins.

Microbial amylolytic enzymes

Starch-degrading, amylolytic enzymes are widely distributed among microbes. Several activities are required to hydrolyze starch to its glucose units. These enzymes include alpha-amylase, beta-amylase, glucoamylase, alpha-glucosidase, pullulan-degrading enzymes, exoacting enzymes yielding alpha-type endproducts, and cyclodextrin glycosyltransferase. Properties of these enzymes vary and are somewhat linked to the environmental circumstances of the producing organisms. Features of the enzymes, their action patterns, physicochemical properties, occurrence, genetics, and results obtained from cloning of the genes are described. Among all the amylolytic enzymes, the genetics of alpha-amylase in Bacillus subtilis are best known. Alpha-Amylase production in B. subtilis is regulated by several genetic elements, many of which have synergistic effects. Genes encoding enzymes from all the amylolytic enzyme groups dealt with here have been cloned, and the sequences have been found to contain some highly conserved regions thought to be essential for their action and/or structure. Glucoamylase appears usually in several forms, which seem to be the results of a variety of mechanisms, including heterogeneous glycosylation, limited proteolysis, multiple modes of mRNA splicing, and the presence of several structural genes.

Purification and characterization of extracellular alpha-amylase and glucoamylase from the yeast Candida antarctica CBS 6678

An alpha-amylase and a glucoamylase were purified to homogeneity from the culture fluid of beta-cyclodextrin-grown Candida antarctica CBS 6678 by protamine sulfate treatment, ammonium sulfate precipitation, gel filtration (Sephadex G-75 sf, Ultrogel AcA 54), DEAE-Sephacel chromatography, hydroxyapatite chromatography and affinity chromatography on acarbose--AH-Sepharose 4B. Both enzymes were monomeric glycoproteins with fairly different amino acid compositions. Their apparent relative molecular mass, sedimentation coefficient (Szero20,w), isoelectric point, absorption coefficient (280 nm), pH and temperature optima were estimated as 48,500, 4.7 S, 10.1, 1.74 cm2 mg-1, 4.2 and 57 degrees C, respectively, for glucoamylase and as 50,000, 4.9 S, 10.3, 1.53 cm2 mg-1, 4.2 and 62 degrees C, respectively, for alpha-amylase. Kinetic analyses indicated that both enzymes preferentially hydrolyzed high-molecular-mass substrates, including some raw starches. alpha-Amylase was active on cyclodextrins, whereas debranching activity was demonstrated for glucoamylase. Trestatins were potent inhibitors of both alpha-amylase (Ki less than 1 microM) and glucoamylase (Ki less than 0.1 microM), being more effective than Bay e 4609 (Ki less than 10 microM). Glucoamylase was selectivity and strongly inhibited by acarbose (Ki less than 0.1 microM). Activity of the latter enzyme was also affected by 1-deoxynojirimycin (Ki less than 1 mM), maltitol and amino alcohols (Ki less than 10 mM). Unlike alpha-amylase, glucoamylase adsorbed strongly onto raw starch, the adsorption site being non-identical with the active site.

Fuels and industrial chemicals through biotechnology. 2

An overview of research on the biotechnical production of fuels and industrial chemicals during the two-year period of 1983-1984 is presented. Ethanol fermentation has continued to be the subject of major interest. A considerable amount of work has been directed to alternative feedstocks such as pentose sugars and lactose, and to bacterial fermentations. Reports on extrusion cooking as a continuous pretreatment method for subsequent ethanol fermentation, and on novel alternative downstream processing techniques have been published. In addition to ethanol fermentation, much attention has been paid to the biotechnical production of 2,3-butanediol, and of a number of organic and amino acids. In general, there appears to be a growing interest in the application of biocatalysis for the production of specialty chemicals, although only a few examples will be discussed in this paper. The construction of a demonstration plant to produce ethanol from molasses by a two 10 kL bed-volume immobilized yeast bioreactors at the Kyowa Hakko Kogyo Company Hofu plant, the announcement by Nitto Chemical Industries Company to begin the biotechnical production of acrylamide, and the French decision to construct pilot plants for the biotechnical production of acetone-butanol-ethanol cosolvent and of ethanol from renewable resources represent major scale-up developments.