Amylase

Marking Eastward. Lowe , in Encyclopedia of Gastroenterology, 2004

Enzymology

α-Amylase, an endoenzyme, preferentially cleaves interior α-1,4 linkages and has very depression activity against the bonds of concluding glucose units. Additionally, it cannot hydrolyze the α-1,half-dozen linkages in amylopectin. The resulting products of amylase acting on starch, referred to equally dextrins, are α-1,iv-linked glucose dimers (maltose), α-1,iv-linked glucose trimers (maltotriose), and branched oligosaccharides of half-dozen to 8 glucose units that comprise both α-ane,6 and α-1,4 linkages (limit dextrins). Starch digestion can begin in the oral cavity and in a swallowed bolus of nutrient, but primarily occurs in the lumen of the upper small intestine. Digestion of starch is completed in the intestine past the castor border enzymes, maltase and isomaltase.

The active site of α-amylase contains multiple subsites, each of which is capable of bounden one glucose residue of the substrate. The porcine and human enzymes appear to have five subsites, and subsite three is probably the catalytic site. Substrates tin can bind with the first glucose balance in subsite 1 or two so that cleavage can occur between the first and second or second and third residues. During a unmarried enzyme–substrate encounter, multiple glucose bonds are cleaved. Three acidic residues, one glutamic acid and two aspartic acids, are thought to be the catalytic residues. The glutamic acid is believed to exist the proton donor and one of the aspartic acids acts as a nucleophile. α-Amylase has an accented requirement for calcium ions and is activated past anions such equally chloride, bromide, iodide, or fluoride. Heavy metals inhibit the enzyme. The importance of serum amylase levels in the diagnosis of acute pancreatitis has generated widespread involvement in its analysis. Amylase is almost commonly measured by absorbance or fluorescence assays in which a labeled substrate is cleaved.

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Bacterial and Yeast Cultures – Process Characteristics, Products, and Applications

Wei-Cho Huang , I-Ching Tang , in Bioprocessing for Value-Added Products from Renewable Resource, 2007

4.ix Industrial enzymes

Amylases besides equally amyloglucosidases are industrial enzymes used in starchsaccharification – converting starch to glucose. α-Amylases, endoenzymes, are produced by Bacillus subtilis, B. amyloliquefaciens and B. licheniformis [104–105]. Pullulanase, known as limit dextrinase, is able to specifically hydrolyze the β-1,6-glycosidic linkages of pullulan to generate maltotriose and break up the 1,4-linkages in amylopectin, which leads to the formation of maltose and glucose [114–115]. Therefore, this enzyme, mainly produced by Bacillus sp., plays a central role in the brewing process and starch hydrolysis [116–117]. Glucose isomerase catalyzes the reversible isomerization of D-glucose to D-fructose or D-xylose to d-xylulose [106]. It is used to produce high-fructose-corn-syrup, a low calorie sweetener. Whole cells of Streptomyces sp., immobilized in a bioreactor, accept been continuously used for the production of glucose isomerase with heat treatment inactivating contamination of other enzymes in the cells [107–110]. The whole cells were employed as non-feasible biocatalysts for biotransformation. In general, single-activity, immobilized cell systems with permeabilizing treatments with heat, surfactants or solvents are required [106].

Many leaner, such every bit B. licheniformis and B. amyloliquefaciens, excrete alkaline proteases [102–103]. Proteases are used primarily in the detergent and dairy industries. They are likewise used for medicine. Lipases have been used for therapeutic purposes every bit digestive enzymes in the dairy industry. Lipases from Candida cylindraceae are used to hydrolyze oils in the soap industry [112]. In improver, lipases from C. rugosa can perform enantioselective esterification to synthesize esters from acids and alcohols in the pharmaceutical industry [140]. Bacillus species produce β-lactamase, an industrial enzyme that catalyzes the hydrolysis of the β-lactam ring in β-lactam antibiotics. β-Lactamase has been used in medicine for the specific assay of penicillins [111].

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Cellulase Systems in Trichoderma

Luis H.F. Do Vale , ... Marcelo Five. de Sousa , in Biotechnology and Biology of Trichoderma, 2014

Degradation of Cellulose by Cellulase Systems

The enzymatic deposition of cellulose is divided into two hydrolysis steps. The master hydrolysis takes place on the cellulose surface. It is primarily dependent on endoenzymes (endoglucanases) that cleave accessible intramolecular β-1,four-glucosidic bonds of cellulose chains randomly in a nonprocessive manner with formation of new chain ends. Furthermore, exoenzymes (exoglucanases) cleave cellulose chains in a processive way at the reducing or nonreducing ends to release cellobiose or glucose ( Fig. 16.1). The rate limiting step is the depolymerization of the insoluble cellulose past the endoglucanases and cellobiohydrolases (Seiboth et al., 2011). The open groove topography of endoglucanases shows a canyon running across the enzyme surface in which the substrate concatenation is accommodated (Henrissat and Davies, 1997; Medie et al., 2012). An extended surface loop of cellobiohydrolases is responsible for creating a tunnel-shaped topography and thus facilitates the mechanism of processive action on the substrate. Medie and coworkers (Medie et al., 2012), has pointed out that cellobiohydrolases may be subdivided into exo- and endo-processive categories on the footing of initial enzymatic assail taking identify solely at concatenation ends or randomly, respectively. Substrate channeling, a process of direct transfer of the product of an enzyme to another proximate enzyme or cell equally its substrate without equilibration with the bulk phase (Zhang, 2011), is a phenomenon likely to occur in the master step of cellulose hydrolysis. The distance between pour enzymes of cellulose-degrading enzymes may greatly influence the caste of substrate channeling. Thus, the distance between the 2 enzyme systems (endoglucanase and cellobiohydrolase) has to be sufficiently close.

Effigy 16.1. The enzymatic breakdown of cellulose. An ensemble of enzymes degrades cellulose by hydrolyzing β-1,4-glucosidic bonds in a synergistic activeness. Endo-β-1,4-glucanases (EBG) or just endoglucanases hydrolyze accessible intramolecular bonds in cellulose chains to generate new shorter bondage. Cellobiohydrolases (CBH) or just exoglucanases human action on ends of cellulose chains (CBHI at reducing end and CBHII at nonreducing end) to release soluble cellobiose, which are then hydrolyzed to glucose by β-glucosidases (BGL). Celloligomers can also be hydrolyzed past some β-glucosidases. (For color version of this figure, the reader is referred to the online version of this volume.)

The secondary hydrolysis that occurs in the liquid phase is carried out by β-glucosidases and releases glucose from cellobiose and cello-oligosaccharide (Nakazawa et al., 2009). β-Glucosidases take active centers that are buried in pockets or caves. Cellulases show mechanisms of acid/base of operations hydrolysis of the glycosidic bonds with retention (double displacement machinery) or inversion (single displacement mechanism) of the anomeric configuration at the cleavage signal (Zechel and Withers, 2000; Bojarová and Kren, 2009; Jordan et al., 2012). Transglycosylation events are restricted to retaining enzymes in which occur transfers of a glycosidic residue from an activated glycoside donor to an acceptor while retaining anomeric configuration (Bojarová and Kren, 2009; Medie et al., 2012).

In addition to enzymes that human activity directly on the β-1,4 linkages in cellulose, nonenzymatic proteins that human action indirectly might likewise exist important in cellulose breakdown without production of detectable hydrolysis sugar. I example for such a nonenzymatic poly peptide is swollenin (Wilson, 2009; Arantes and Saddler, 2010; Jäger et al., 2011). Swollenin, a plant expansin-like poly peptide, is reported to play an important role in the initial stage in enzymatic saccharification of cellulose (amorphogenesis). The name swollenin is due to its power to swell cotton fibers without producing detectable amounts of reducing sugars (Brotman et al., 2008). In this case, the mechanism underlying the action involves the disruption of hydrogen bonding between cellulose fibrils by the nonhydrolytic activeness of swollenin and thereby enhancing enzymatic hydrolysis of cellulose (Seiboth et al., 2011; Zhou et al., 2011). Another examples of amorphogenesis are mediated by carbohydrate binding module (CBM) of cellobiohydrolase I, expansin, and GH61 (Karkehabadi et al., 2008; Koseki et al., 2008; Arantes and Saddler, 2010). The primary role of CBMs is to anchor the catalytic module to cellulose, although the possibility cannot be ruled out that CBM has an agile office in the nonhydrolytic release of single cellulose chains from highly ordered and tightly packed fibrillar regions of the cellulose microfibrils (Klyosov, 1990; Arantes and Saddler, 2010). The machinery proposed for cellulose dispersion suggests that CBM of cellulases are adsorbed to disturbances in the crystalline structure of cellulose (microcracks), followed by their penetration into the interfibrillar spaces and dispersion of the cellulose structure (Klyosov, 1990; Arantes and Saddler, 2010). Every bit a upshot of mechanical pressure on the cavity walls by CBM of cellulases, swelling of the cellulose construction occurs and water molecules are accommodated between the microfibrils. This process leads to further penetration of water molecules inside the capillary infinite, cleavage of hydrogen bonds between the cellulose chains and formation of free concatenation ends, resulting in the disassociation of the individual microfibrils. The process of enzyme adsorption prevents the solvated chains and free concatenation ends from realigning and readhering.

Expansins (constitute-derived proteins) and GH61 proteins are proposed to increase the activity of cellulases on lignocellulose substrates, disrupting noncovalent bonds within cellulose microfibrils and between other cell wall polysaccharides attached to the microfibrils and making the glucan chains within the microfibrils more attainable to cellulase attack (Merino and Crimson, 2007).

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Methods for Analysis of Golgi Complex Function

Romain Péanne , ... François Foulquier , in Methods in Cell Biology, 2013

ten.2.1.three.3 Release of the oligosaccharide moiety from newly synthesized glycoproteins

Even if chemic cleavage can be used to release the newly formed oligommanoside-type glycans, we recommend releasing the oligosaccharide moiety from newly synthesized glycoproteins with the endoenzyme peptide- N-glycanase (PNGase).

First, go on to the proteolytic digestion of the protein pellet. Begin by completely drying the pellet under a stream of nitrogen. Then, resuspend the dried pellet in 300   μl of 0.i   G ammonium bicarbonate buffer, pH vii.ix, containing 1   mg/ml of trypsin. Digest overnight at room temperature. The following day, inactivate trypsin activity by incubation for 10   min at 100   °C before to put the sample nether a stream of nitrogen to eliminate the ammonium bicarbonate.

Once the proteins digested, deliquesce the dried pellet in 100   μl of fifty   mM phosphate buffer, pH 7.2 and 0.5 units of PNGAse F. Incubate the glycoproteins for 4   h at 37   °C, to release the oligosaccharides from the peptides.

To purify the released labeled oligosaccharides, add together 1   ml of l   mM phosphate buffer, pH seven.2 to the reaction and deposit the full volume (1.1   ml) on a Bio-Gel P2 column. Proceed then equally described in Section 10.2.1.3.ane.

Structural analysis of the released labeled oligosaccharides can then be performed by HPLC equally described farther.

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MALT | Chemistry of Malting

Grand.S. Izydorczyk , G.J. Edney , in Encyclopedia of Food Sciences and Nutrition (Second Edition), 2003

α-Amylases

The α-amylases are able to hydrolyze intact starch granules with the formation of soluble products. They are responsible for the initial deposition of starch granules during malting. α-Amylases (EC 3.2.1.ane) are endoenzymes that cleave internal α-(ane → 4) glucosyl linkages of amylose and amylopectin in a random mode. They are unable to hydrolyze the α-(ane → 6) glucosyl linkages at the branch points in amylopectin. Their hydrolytic action is slower on brusk bondage, and they vary in their ability to hydrolyze the α-(i → four) linkages in close proximity to the branch points. α-Amylases, acting on their own, are able to degrade amylose to a mixture of shorter linear α-glucan bondage (linear α-dextrins), oligosaccharides, maltose, and glucose. Amylopectin, nevertheless, is degraded to a bottom extent, yielding a mixture of still big branched fragments (branched α-dextrins) also as some linear oligosaccharides, maltose and glucose ( Figure half dozen). Two isoenzymes of α-amylases with the aforementioned apparent substrate specificities and action patterns, but unlike properties, are synthesized in germinating barley (Table 2).

Figure 6. Summary of the modes of action of some enzymes important in degradation of starch polymers. Glc, d-glucopyranose residue; −, α-(1 → 4)-link; ↑, α-(one → 6)-link; NR, nonreducing end; R, reducing cease.

Table 2. Properties of α-amylase I and II from germinating barley a

Holding α-Amylase I α-Amylase Two
Molecular weight 45 342 45 005
Isoelectric point 4.8–5.3 five.nine–half-dozen.6
pH optimum iii.0–five.five 5.0–5.4
Stability at pH 3.six Relatively stable Unstable
Reaction with endogenous inhibitor b No inhibition Strong inhibition
Ca2+ binding Very strong Potent
Major secretion site Aleurone Aleurone
Proportion in germinating grain Minor (up to 10%) Major (up to ninety%)
a
Information compiled from Briggs DE (1992) Barley germination: biochemical changes and hormonal control. In: Shewry PR (ed.) Barley: Genetics, Biochemistry, Molecular Biology and Biotechnology, pp. 369–401. Wallingford, Britain: CAB International; Hill RD and MacGregor AW (1988) Cereal α-amylases in grain enquiry and technology. In: Pomeranz Y (ed.) Advances in Cereal Science and Technology, vol. IX, pp. 217–261. St. Paul, MN: American Clan of Cereal Chemists; and MacGregor EA and MacGregor AW (1987) Studies of cereal α-amylase using cloned DNA. CRC Disquisitional Reviews in Biotechnology 5: 129–142.
b
Barley α-amylase/subtilisin inhibitor.

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The Cellulosome

Nienwen Chow , J. H. David Wu , in Biotechnology of Microbial Enzymes, 2017

10.1 Introduction

Plant biomass consisting of lignocellulosic materials is the most abundant organic matter on earth. Its degradation in nature is catalyzed by a myriad of microbial biomass-degrading enzymes including cellulases, hemicellulases, and ligninases. The best-studied cellulase/hemicellulase system is from the fungus Trichoderma reesei. T. reesei produces various exo- and endo-β-glucanases, and hemicellulases. These secreted enzymes are costless (monomeric) proteins and it has also been established that enzymatic cellulose degradation is facilitated by the synergistic action betwixt exo- and endo-β-glucanases.

To dethrone a crystalline cellulose, the endo-enzyme outset makes a nick on the cellulose chain, creating reducing and nonreducing ends, respectively. Exo-enzymes and so remove cellobiose units in a step-wise fashion from the chain ends, ultimately leading to consummate deposition of the crystalline cellulose. In this mode of activeness, the endo-enzyme is expected to lengthened away from the site of the nick to vacate the infinite for the exo-enzymes. The enzyme diffusion process appears to be tedious and less efficient than if the endo- and exo-enzymes would course a complex and work collaboratively on the site of degradation. All the same, the enzyme, once secreted, can be quickly diluted in the extracellular environment, making complex formation less favorable. Instead, the fungus appears to recoup for the relative inefficiency of monomeric proteins by producing a large quantity of extracellular proteins to ensure synergism among these enzymes.

In the early on 1980s, scientists who studied the cellulase system of Clostridium thermocellum, a thermophilic and anaerobic bacterium, discovered that it exists mainly in the course of a mysterious large protein aggregate. The aggregate was later termed "the cellulosome" (Lamed et al., 1985). The ensuing inquiry for the next two to iii decades, aided by the availability of the genome sequence every bit well as mod biophysical and bioinformatics tools, has revealed that the cellulosome is a well-organized supramolecular assembly that works equally a molecular machine, in a cell-bound or prison cell-complimentary mode, for cellulosic biomass deposition. In this chapter, the composition, structure and assembly of the cellulosome of C. thermocellum will be described.

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Chemic Structure Analysis of Starch and Cellulose Derivatives

Petra Mischnick , Dane Momcilovic , in Advances in Carbohydrate Chemical science and Biochemistry, 2010

(i) General

As mentioned in the introductory part of this commodity, forth with chemical methods, enzymes are attractive tools in the analysis of chemical structure. The application of enzymes for unmodified polysaccharides was surveyed in this series by McCleary and Matheson in 1986. 295 Chemical modification of polysaccharides directly affects their enzymatic digestibility with respect to blazon, degree, and patterns of substitution. To understand these relationships it is necessary to provide some general information on enzymes selective for starch and cellulose.

Enzymes that catalyze hydrolysis of such O-glycosyl compounds as cellulose and starch are termed glycosidases. Some enzymes human activity more efficiently on polymeric substrates, whereas others are more than efficient on oligomeric substrates and hydrolyze these into mono- or di-saccharides (which may and so be further metabolized). The enzymes that are described here are named according to the "Enzyme List" of the Articulation Commission on Biochemical Classification (JCBN) of the International Wedlock of Pure and Applied Chemistry and the Nomenclature Committee of the International Union of Biochemistry and Molecular Biological science.

Glycosidases selective for starch and cellulose are commonly referred to as glucanases, since they catalyze depolymerization of glucose-based polysaccharides. Glucanases are subdivided as either endo- or exo-enzymes. endo-Enzymes randomly carve the glucosidic linkages of the polysaccharide, whereas exo-enzymes deed from the nonreducing and, in some cases, from the reducing end of the substrate. The endo-enzymes produce polymeric and/or oligomeric compounds (depending on the DP of the substrate and cleavage indicate), which may be farther hydrolyzed to smaller compounds. exo-Enzymes, on the other hand, produce monomeric or oligomeric compounds past successive cleavage, usually from the nonreducing end. It should be pointed out that some enzymes are non distinct with respect to endo- or exo-style of action, but rather have a preference for i of them. 296,297

Mutual for all cellulose- and starch-selective glucanases is their substrate-binding active site, which usually contains several subsites (Fig. 33). A subsite is comprised of i to several amino acrid residues, which interact with one of the glucose residues in the substrate. During hydrolysis the substrate is bound to the subsites, as past hydrogen bonds betwixt the substrate OH groups and the amino acrid residues on the enzyme. The number of subsites varies betwixt different enzymes. In addition, it has been shown that, for some enzymes it is not necessary for all subsites to be occupied in order for hydrolysis to occur. 298,299

Fig. 33. Schematic representation of the agile site of a glucanase comprised of six subsites.

Subsites are numbered according to Davies et al. 300 The arrow (Fig. 33) indicates the glucosidic linkage that is hydrolyzed and "Due north" and "R" refer to the nonreducing and the reducing end, respectively.

In the classification that has been proposed past Henrissat, glycosidases are grouped into families on the basis of similarities in their amino acid sequence. 301,302 This classification was later on practical in a scheme for enzymes that hydrolyze β-(1→4)-linked plant prison cell-wall polysaccharides. 303 According to this scheme, an enzyme is named Xx YyyNZ, where Xx refers to the organism of origin, Yyy is the favored substrate, N is the enzyme family, and Z indicates which one in the order of family N enzymes that is being referred to (if more than one are known). For example, the fungus Trichoderma reesei produces two family unit 7 enzymes, cellobiohydrolase I and endoglucanase I. According to the scheme they are named Tr Cel7A and Tr Cel7B, respectively.

The mechanism of action of glucanases is strongly influenced by the shape and structure of the active site. exo-Enzymes ordinarily take a pocket or a tunnel-shaped active site, which "forces" the enzyme to attack a chain end of the polysaccharide substrate. 304 The active site of endo-enzymes has the shape of a fissure. endo-Enzymes can therefore demark to the substrate randomly along the polymeric backbone (provided that the active site can arrange the sequence of the polysaccharide). Furthermore, some glucanases also contain a binding domain, which enables reversible sorption onto (and, thus, hydrolysis of) nondissolved polysaccharides, such every bit granular starch and fibrous cellulose. 305,306

Fig. 34 shows schematic structures of amylopectin, amylose, and cellulose and also indicates where different glucanases attack these polysaccharides. Alpha-amylases (EC iii.2.1.one) are endo-enzymes, which hydrolyze α-(1→4) glucosidic linkages in amylopectin and amylose (Fig. 34A). In amylopectin, the A, B, and C chains are hydrolyzed past these enzymes, whereas the α-(1→half dozen) glucosidic linkages in the branching points of amylopectin are not attacked. These linkages can be hydrolyzed by pullulanases (EC three.2.1.41) and isoamylases (EC three.2.i.68).

Fig. 34. Schematics of amylopectin (A), amylose (B), and cellulose (C), and the selectivity of various glucanases on these polysaccharides.

Beta-amylases (EC 3.2.i.2) (Fig. 34A,B) are exo-enzymes that attack the substrate from the nonreducing end and hydrolyze α-(ane→4) glucosidic linkages. Maltose (disaccharide) molecules are successively discrete from the non-reducing terminate during hydrolysis by beta-amylase. In addition, glucan (i→iv)-α-glucosidases (EC three.two.1.3, as well known as amyloglucosidases or glucoamylases) hydrolyze α-(1→4)- and α-(1→half dozen) glucosidic linkages from the nonreducing end, yielding d-glucose. 38 (Note that the term "amyloglucosidase" is used throughout this article, since information technology is more oft encountered in the literature.) Whereas beta amylases and amyloglucosidases accept higher activeness on polysaccharides as compared to oligosaccharides, the reverse is the case for α-glucosidases (EC 3.2.1.20). These exo-enzymes efficiently degrade maltose and other α-(1→four)-linked [and in some cases α-(1→6)-linked] oligosaccharides to glucose.

Cellulose-selective endo-enzymes are sometimes referred to equally cellulases (EC 3.two.1.4, Fig 34c), which is also the definition according to JCBN. However, recognizing that "cellulase" is not always equivalent to "cellulose selective endo-enzyme" in the literature, we use the proper name "endoglucanase" throughout this article. Examples of exo-enzymes are β-(1→4)-cellobiosidases (cellobiohydrolases) (EC 3.ii.ane.91) and β-glucosidases (cellobiases) (EC iii.2.1.21). β-(1→4)-Cellobiosidases may assault the substrate on the nonreducing or reducing terminus, whereas β-glucosidases only attack on the nonreducing end, with the production of glucose. β-Glucosidases also efficiently hydrolyze cellobiose to glucose.

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The Importance of the Measurement of Enzyme Activity in Botanical and Agricultural Chemistry

Eduard Hofmann , in Methods of Enzymatic Analysis, 1965

I Enzyme Activity in Soil

The root system and aerial parts of plants become incorporated into the soil on the death of the plant. The type and extent of their bacterial decomposition determines the quantity and the quality of the humus formed, which is of importance for the fertility of the soil. The enzymes contained in soil can be divided into ectoenzymes and endoenzymes.

Ectoenzymes are released from living micro-organisms. They attack organic substances of high molecular weight, which cannot be absorbed past the bacteria.

Endoenzymes occur in the soil later on the decease of the micro-organisms. Because soils commonly have a high content of dirt and humic substances, they accept a high buffer and absorption capacity. Dead micro-organisms practice not decay by putrefaction, only rather by autolysis which liberates the endoenzymes. They withstand decomposition (adsorbed on clayey minerals) and remain agile for a long menstruation.

Consequently a profile of enzyme action occurs in soil, which is produced by the micro-organisms and is maintained by them. The profile is to a slight extent contributed to past the enzyme content of the leaner, which are living in the soil at the fourth dimension of the collection of the sample. This contribution is subject to the same seasonal and other variations as the bacterial count. By far the largest fraction of the enzymes are excreted ectoenzymes and endoenzymes which are set free by the autolysis of the older, dead leaner and are retained in the soil.

Therefore the level of enzyme activeness in soil is not subjected to the aforementioned variations every bit bacterial counts. It changes only slowly, and and then simply when the number of micro-organisms is increased or lowered for a long period due to the method of cultivation. Natural phenomena make no divergence or are scarcely noticeable.

For the evaluation of the measured enzyme activity information technology is necessary to take into account the type of soil (sand, loam or humus) and the type of cultivation in recent years. Sandy soil has only slight, loamy soil average and humus loftier enzyme activity. In improver, the pH of the soil has a great effect. Acid soils comprise relatively few micro-organisms and consequently only low enzyme activity. The nearer the pH is to neutrality, the higher is the enzyme activity. In arable and garden soils the enzymes are evenly distributed in the topmost layer of the soil (about 20 cm.) considering of frequent tillage. Their action is only half as much as in pasture soil of a like blazon, where the enzyme activity is restricted to the upper, well rooted layer of virtually 5 cm. and quickly falls off with increase in depth ("enzyme profile of the soil"). Organic substances (remains of roots, stable manure, dark-green manure, peat and humus substances) increment the enzyme content by promoting the growth of the bacteria. The same is true of efficient tilling of the soil (aeration). Bad aeration and excessive cultivation are injurious, the former by reducing and the latter by temporarily increasing oxidative processes which destroy organic substances and therefore very before long stop the growth of the micro-organisms.

Special cases are garden soils, forest soils and soils which have been particularly cultivated for many years (soil on which hops accept been grown). About twice the enzyme activity is plant in garden soils equally in abundant soils. After many years of ane crop culture (e.g. hops, asparagus, strawberries) the enzyme activity falls to near half that in next abundant soils because of the skillful manuring and tillage. Simply the urease activeness increases (up to double), due to the use of large amounts of stable manure and other organic substances.

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Forest Products: Biotechnology in Pulp and Paper Processing

L. Viikari , ... A. Ragauskas , in Encyclopedia of Microbiology (Third Edition), 2009

Other hemicellulases and glucanases

The side groups connected to xylan and glucomannan master chains can exist cleaved by α-glucuronidase (EC three.2.ane.131), α-arabinosidase (EC 3.2.one.55), and α-d -galactosidase (EC 3.two.1.22). Acetyl substituents bound to hemicellulose are removed by esterases (EC 3.1.one.72). Most of the side-group cleaving enzymes are able to assault only on oligomeric substrates produced by the courage-depolymerizing endoenzymes, that is, xylanases and mannanases. A few are capable of also attacking intact polymeric substrates. Even most accessory enzymes of the latter type, nonetheless, prefer oligomeric substrates.

Specific xyloglucanases or xyloglucan-specific EGs stand for a new class of polysaccharide-degrading enzymes which can assail xyloglucans. The distinction between endoxyloglucanases and endocellulases plain lies in the requirement for specific side groups in the case of the xyloglucanases. Xyloglucan endotransglycosylase, XET (EC 2.iv.ane.207) is able to transfer fragments from donor xyloglucans to suitable acceptors, such as a xyloglucan-derived nonasaccharides. Because of the inherent power of XET to catalyze transglycosylation rather than hydrolysis, this enzyme has potential for fiber modification.

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Volume 1

Eric A. Johnson , Carlos Echavarri-Erasun , in The Yeasts (5th Edition), 2011

4.3 Schwanniomyces (Debaryomyces) Occidentalis

Schwanniomyces occidentalis is a member of the Saccharomycetales, and is closely related to sure species of Debaryomyces and Candida (Kurtzman 2003, Kurtzman and Robnett 2003, Suh et al. 2006b). Schwan. occidentalis is of biotechnological interest primarily considering of its production of hydrolytic enzymes, especially its active amylolytic system (Ingledew 1987, Wang et al. 1999). The amylolytic arrangement is capable of degrading complex sources of starch from a variety of sources, including white potato, barley, corn, wheat, and others. The amylase system is primarily comprised of endo-enzymes that hydrolyze starch to maltose, maltotriose, and higher oligosaccharides, with release of comparatively small quantities of glucose. Schwan. occidentalis has been used in minor-scale industrial processes, such as food fermentations performed in developing countries. The efficient production of sugars and sugar syrups past Schwan. occidentalis has likewise been exploited for low volume production of ethanol, and single-prison cell protein (SCP). For large-scale processes, the more than potent and thermostable amylase systems from Bacillus sp. and filamentous fungi including species of Aspergillus and Trichoderma are mainly used industrially (Aehle 2004, Pandey et al. 2006). Schwan. occidentalis has been considered for production of heterologous proteins, and certain other products (Wang et al. 1999).

Schwanniomyces occidentalis is also capable of degrading glycogen and utilizes a variety of carbon sources including glucose, fructose, xylose, raffinose, lactose (some strains), cellobiose, ethanol, and alkanes. Schwan. occidentalis can form upwardly to about 6% ethanol (five/v) by fermentation (Jamal et al. 2007), and higher concentrations have been achieved in co-culture with Southward. cerevisiae. Several of its starch-degrading enzymes have been cloned and expressed in S. cerevisiae at iii– to half dozen–fold higher levels than achieved in Schwan. occidentalis (Ghang et al. 2007, Kang et al. 2003). Other amylolytic yeasts of potential biotechnological value include Lipomyces kononenkoae and Saccharomycopsis fibuligera (Know et al. 2004).

Schwanniomyces occidentalis produces phytase action, which is a valuable enzyme for the utilization of phytates every bit a sole source of phosphate (Kaur et al. 2007). Phytases take considerable commercial and environmental importance, since they catalyze the release of phosphate from phytate, which is the major course in which organic phosphorous is stored in plant seeds and grains (Kaur et al. 2007). Currently, most commercial phytases are produced by filamentous fungi (Aehle 2004, Pandey et al. 2006). Schwan. occidentalis likewise produces killer proteins and antifungal substances, and the yeast has been considered for biocontrol of undesirable fungi (Chen et al. 2000).

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