scholarly journals Revisiting the Phenomenon of Cellulase Action: Not All Endo- and Exo-Cellulase Interactions Are Synergistic

Catalysts ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 170
Author(s):  
Mariska Thoresen ◽  
Samkelo Malgas ◽  
Mpho Mafa ◽  
Brett Pletschke
Keyword(s):  
Reducing Sugars ◽  
Cellulose Hydrolysis ◽  
Mass Ratio ◽  
Biomass Degradation ◽  
Cellulose Chain ◽  
Critical Step ◽  
Protein Mass ◽  
Lack Of Information ◽  
Synergistic Relationships ◽  
Microbial Sources

The conventional endo–exo synergism model has extensively been supported in literature, which is based on the perception that endoglucanases (EGs) expose or create accessible sites on the cellulose chain to facilitate the action of processive cellobiohydrolases (CBHs). However, there is a lack of information on why some bacterial and fungal CBHs and EGs do not exhibit synergism. Therefore, the present study evaluated and compared the synergistic relationships between cellulases from different microbial sources and provided insights into how different GH families govern synergism. The results showed that CmixA2 (a mixture of TlCel7A and CtCel5A) displayed the highest effect with BaCel5A (degree of synergy for reducing sugars and glucose of 1.47 and 1.41, respectively) in a protein mass ratio of 75–25%. No synergism was detected between CmixB1/B2 (as well as CmixC1/C2) and any of the EGs, and the combinations did not improve the overall cellulose hydrolysis. These findings further support the hypothesis that “not all endo-to exo-cellulase interactions are synergistic”, and that the extent of synergism is dependent on the composition of cellulase systems from various sources and their compatibility in the cellulase cocktail. This method of screening for maximal compatibility between exo- and endo-cellulases constitutes a critical step towards the design of improved synergistic cellulose-degrading cocktails for industrial-scale biomass degradation.

scholarly journals Eco-Friendly Ca-Montmorillonite Grafted by Non-Acidic Ionic Liquid Used as A Solid Acid Catalyst in Cellulose Hydrolysis to Reducing Sugars

Molecules ◽  
2019 ◽  
Vol 24 (9) ◽  
pp. 1832 ◽  
Author(s):  
Yang Zhou ◽  
Miao Yang ◽  
Dongshen Tong ◽  
Haiyan Yang ◽  
Kai Fang
Keyword(s):  
Ionic Liquid ◽  
Reducing Sugars ◽  
Batch Reactor ◽  
Solid Acid Catalyst ◽  
Cellulose Hydrolysis ◽  
Solid Catalyst ◽  
Mass Ratio ◽  
Acidic Ionic Liquid ◽  
Hydrolysis Of Cellulose ◽  
Hydrolysis Of

An effective and friendly method was developed for the production of reducing sugars (RS) from the hydrolysis of cellulose over the solid catalyst of Ca-montmorillonite (Mt) grafted by non-acidic ionic liquid (Mt-IL) in water. The effect of mass ratio, water dosage, reaction temperature, and time were investigated in a batch reactor. Raw Mt showed only a 7.9% total reducing sugars (TRS) yield for the catalytic hydrolysis of cellulose in water. As the Mt was grafted by -SO3H and IL, the TRS yield greatly increased under the same reaction conditions. The highest TRS yield of 35.7% was obtained on the catalyst of Mt grafted by non-acidic IL at 200 °C with the mass ratio of catalyst to cellulose of 0.2 for 120 min. The high TRS yield for Mt-IL should be attributed to the synergistic effect of the dissolution of cellulose by IL and the exposed metal ions on the layer with water. Although the yield of TRS on Mt-IL decreased gradually with recycling runs, the decrease after the first run was not very serious compared to the fresh catalyst. This work provides a promising strategy for efficient cellulose hydrolysis into fine chemicals by Mt with non-acidic IL.

Cellulose Hydrolysis by Acidic Ionic Liquids Enhanced with Microwave Heating

2018 ◽  
Vol 1145 ◽  
pp. 75-79 ◽  
Author(s):  
Hai Yun Ma ◽  
Zhi Ping Zhao ◽  
Peng Lu
Keyword(s):  
Ionic Liquids ◽  
Microwave Heating ◽  
Reducing Sugars ◽  
Cellulose Hydrolysis ◽  
Degree Of Polymerization ◽  
Deionized Water ◽  
Acidic Ionic Liquids ◽  
Hydrolysis Of Cellulose ◽  
Total Reducing Sugars ◽  
Hydrolysis Of

The hydrolysis of cellulose into platform compounds and chemicals fuels has gained much attention to relieve the global energy crisis and environmental pollution. The filter paper (FP) cellulose with average degree of polymerization (DP) of 1000-1300 was dissolved in 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) firstly. And then acidic ionic liquids (ILs), ([(CH2)3SO3HVIm]HSO4) as the catalyst was applied to hydrolyze the FP cellulose by microwave heating. Compared with the oil bath heating method, microwave heating could effectively increase the total reducing sugars (TRS) yield about 10.7%. When the ratio of ILs catalyst to FP (w/w) was 0.167, and the ratio of deionized water to FP (w/w) was 0.833, the TRS yield was up to 60.8% within 20 min at 100°C.

scholarly journals The effect of beta-glucosidase supplementation on enzymatic hydrolysis of cellulose in hydrothermally pretreated sugar beet shreds

2018 ◽  
pp. 1-9
Author(s):  
Mirjana Antov ◽  
Aleksandar Fistes
Keyword(s):  
Enzymatic Hydrolysis ◽  
Sugar Beet ◽  
Reducing Sugars ◽  
Cellulose Hydrolysis ◽  
Enzymatic Hydrolysis Of Cellulose ◽  
Untreated Material ◽  
Hydrolysis Of Cellulose ◽  
Beta Glucosidase ◽  
Hydrolysis Of

Sugar beet shreds were pretreated by hydrothermal procedure to investigate the effect of beta-glucosidase supplementation at different substrate loading on the rate of cellulose hydrolysis. Cellulose in the hydrothermally pretreated substrate was more efficiently hydrolyzed by enzymes than in untreated material, resulting in more than two times higher release of reducing sugars. In the investigated range of solids load, supplementation of fungal cellulases cocktail by beta-glucosidase increased production of reducing sugars from substrates, while 0.25 U/g was sufficient to achieve the highest effect under applied conditions.

Enzymatic hydrolysis of cellulosic materials by Sclerotium rolfsii culture filtrate for sugar production

1979 ◽  
Vol 25 (6) ◽  
pp. 773-783 ◽  
Author(s):  
J. G. Shewale ◽  
J. C. Sadana
Keyword(s):  
Rice Straw ◽  
Culture Filtrate ◽  
Reducing Sugars ◽  
Sclerotium Rolfsii ◽  
Cellulose Hydrolysis ◽  
Enzyme Concentration ◽  
Sugar Production ◽  
Batch Experiments ◽  
Substrate Level ◽  
Hydrolysis Of

The hydrolysis of purified celluloses (cotton, Avicel, Cellulose-123, Solka Floc SW40) and cellulosic wastes (rice straw, sugarcane bagasse, wood powders, paper factory effluents) by Sclerotium rolfsii CPC 142 culture filtrate was studied. Factors which effect saccharification such as pH, temperature, enzyme concentration, substrate concentration, produce inhibition, adsorption, and inactivation of enzyme and particle size were studied.Virtually no inhibition (<3%) of cellulose hydrolysis by the culture filtrate was observed by cellobiose and glucose up to 100 mg/mL. Filter paper degrading enzyme(s) (but neither carboxymethylcellulase nor β-glucosidase) was adsorbed on cellulose. The n value in the S. rolfsii system was calculated to be 0.32 for Avicel P.H. 101 and 0.53 for alkali-treated (AT) rice straw indicating penetration of cellulase into AT rice straw. In batch experiments at 10% substrate level, solutions containing 6 to 7%, 3.8 to 4.7%, 4.0 to 5.1%, and 4.2 to 4.9% reducing sugars were produced in 24 to 48 h from AT rice straw, AT bagasse, alkali – peracetic acid treated mesta wood and paper factory sedimented sludge effluent, respectively. The main constituent in the hydrolysate from cellulose was glucose with little or no cellobiose, probably due to the high cellobiase content in the culture filtrate.

scholarly journals Analysis of pretreatments of sugar beet shreds for bioethanol production in respect of cellulose hydrolysis and waste flows

2011 ◽  
pp. 223-230
Author(s):  
Darjana Ivetic ◽  
Vesna Vasic ◽  
Marina Sciban ◽  
Mirjana Antov
Keyword(s):  
Enzymatic Hydrolysis ◽  
Sugar Beet ◽  
Reducing Sugars ◽  
Cellulose Hydrolysis ◽  
Raw Material ◽  
Bioethanol Production ◽  
Lignin Removal ◽  
Chemical Pretreatments ◽  
Hydrolysis Of

This paper analyzes some chemical pretreatments of sugar beet shreds concerning generated waste flows and yield of reducing sugars obtained by enzymatic hydrolysis of pretreated material. Waste flows produced in pretreatments of sugar beet shreds originated from pectin and lignin removal from raw material. Suitability of substrates prepared in single and two-step pretreatment procedure for enzymatic hydrolysis was determined based on the yield of reducing sugars released by cellulase action on them, while different possibilities of processing of wastewaters were discussed based on the characteristic of waste flows.

scholarly journals Processive Endoglucanase Active in Crystalline Cellulose Hydrolysis by the Brown Rot Basidiomycete Gloeophyllum trabeum

2005 ◽  
Vol 71 (5) ◽  
pp. 2412-2417 ◽  
Author(s):  
Roni Cohen ◽  
Melissa R. Suzuki ◽  
Kenneth E. Hammel
Keyword(s):  
Extracellular Enzymes ◽  
Reducing Sugars ◽  
Soluble Sugars ◽  
Brown Rot ◽  
Cellulose Hydrolysis ◽  
Major Product ◽  
Crystalline Cellulose ◽  
Gloeophyllum Trabeum ◽  
Processive Endoglucanase ◽  
Brown Rot Fungus

ABSTRACT Brown rot basidiomycetes have long been thought to lack the processive cellulases that release soluble sugars from crystalline cellulose. On the other hand, these fungi remove all of the cellulose, both crystalline and amorphous, from wood when they degrade it. To resolve this discrepancy, we grew Gloeophyllum trabeum on microcrystalline cellulose (Avicel) and purified the major glycosylhydrolases it produced. The most abundant extracellular enzymes in these cultures were a 42-kDa endoglucanase (Cel5A), a 39-kDa xylanase (Xyn10A), and a 28-kDa endoglucanase (Cel12A). Cel5A had significant Avicelase activity—4.5 nmol glucose equivalents released/min/mg protein. It is a processive endoglucanase, because it hydrolyzed Avicel to cellobiose as the major product while introducing only a small proportion of reducing sugars into the remaining, insoluble substrate. Therefore, since G. trabeum is already known to produce a β-glucosidase, it is now clear that this brown rot fungus produces enzymes capable of yielding assimilable glucose from crystalline cellulose.

Mass-Dependent Cross-Signaling between TXA2 and PAF Receptors.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 1557-1557
Author(s):  
Jin-Sheng Huang ◽  
Lanlan Dong ◽  
Guy C. Le Breton
Keyword(s):  
G Protein ◽  
G Proteins ◽  
Mass Ratio ◽  
G Protein Coupling ◽  
Expression Levels ◽  
Protein Coupling ◽  
Ligand Affinity ◽  
Protein Mass ◽  
Protein Partners ◽  
Mass Dependent

Abstract We have previously demonstrated in human platelets that G-protein coupled receptors (GPCRs) which share a common G” subunit have the capacity to cross-signal when exposed to their respective ligands. This ligand-dependent cross-signaling was shown to involve a redistribution of GPCR-coupled G” subunits, a consequent shift in GPCR ligand affinity and a synergistic effector response (Djellas, et al. 1998; PNAS,95:10944 and Djellas, et al. 2000; Biochem.Pharmacol.59:1521). Based on these findings, we proposed that the phenomenon of ligand-dependent cross-signaling represents one manifestation of a more general process by which cells can dynamically regulate their different GPCR signaling priorities in response to various stimuli. In this model, the relative signaling capacity through different GPCRs is determined by the distribution of G proteins amongst the different GPCRs at a given point in time. The model further predicts that this G protein distribution is not only modulated by ligand-induced shifts in GPCR:G protein coupling affinities (ligand-dependent cross-signaling), but also by shifts in GPCR:G protein mass ratios (mass-dependent cross-signaling), such as those that may occur by up- or down-regulation of GPCRs or their respective G protein partners. The present study examined this mass-dependent GPCR cross-signaling process. Specifically, we established a series of cell lines in which the expression levels of thromboxane A2 receptors (TPR) and platelet activating factor receptors (PAFR) can be progressively altered. These expression systems allowed an alteration of the GPCR:G protein mass ratio for specific GPCRs, i.e., TPR and PAFR. Using radioligand binding analysis and Western blot, we provide evidence that up-regulating TPR expression levels increased the TPR:G-protein mass ratio. This TPR up-regulation resulted in a reduced TPR ligand affinity for [3H] SQ29548. Thus increasing the mass of TPR relative to its G protein partners (Gq or G13) shifted TPRs to a lower ligand affinity state. A similar reduction in PAFR ligand affinity was observed when the PAFR:G-protein mass ratio was increased by elevating PAFR expression levels. Moreover, using an inducible TPR/PAFR co-expressing cell line, increasing the expression level of one of the receptors resulted in reduced ligand affinity for both receptors. Taken in combination with our previous studies, these findings suggest that increasing TPR: G protein mass ratio results in a shift in the TPR-G protein coupling status, such that a larger fraction of total TPR is in the uncoupled state. This reduction in TPR-G protein coupling in turn leads to lower TPR ligand affinity. The finding that expression of TPR also causes reduced ligand affinity for a separate GPCR, i.e. PAFR, suggests that there is a dynamic equilibrium between the distribution of G proteins amongst GPCRs, and that this equilibrium can be altered by changes in the GPCR: G protein mass ratio. In summary, both ligand-dependent and mass-dependent GPCR cross-signaling appear to result from a general mechanism by which cells modulate their GPCR-G protein coupling status, and hence their GPCR ligand affinities and signaling priorities.

scholarly journals ENZYMATIC HYDROLYSIS OF SOLUBLE CELLULOSE DERIVATIVES AS MEASURED BY CHANGES IN VISCOSITY

1950 ◽  
Vol 33 (5) ◽  
pp. 601-628 ◽  
Author(s):  
Hillel S. Levinson ◽  
Elwyn T. Reese
Keyword(s):  
Enzymatic Hydrolysis ◽  
Intrinsic Viscosity ◽  
Reducing Sugars ◽  
Enzyme System ◽  
Molecular Size ◽  
Cellulose Hydrolysis ◽  
Reducing Sugar ◽  
Cellulose Derivatives ◽  
Enzyme Preparations ◽  
Hydrolysis Of

Observation of changes in fluidity is presented as a method for following the enzymatic hydrolysis of soluble cellulose derivatives. The activity of different cell-free enzyme preparations may be compared by this method, providing certain precautions are observed. In general, results obtained by use of the fluidity method are similar to those obtained using the reducing sugar technique, indicating that the same enzyme system is measured by the two methods. Changes in the DP of the substratum may be followed within certain limits of molecular size. Results indicate that a random splitting of CMC occurs during enzymatic hydrolysis, with a concomitant decrease in intrinsic viscosity and an increase in reducing sugars. Certain inadequacies of the cellulose-cellobiose-glucose theory, together with more recent findings, have led to the postulation of an alternate explanation of the mechanism of cellulose hydrolysis.

scholarly journals INFLUENCE OF THE AGE AT THE FIRST INSEMINATION ON THE PRODUCTIVE LONGEVITY OF BLACK AND WHITE AND KHOLMOGORY COWS

2019 ◽  
Vol 51 (3) ◽  
pp. 58-63
Author(s):  
T.A. Russkikh ◽  
◽  
V.A. Bychkova ◽  
Keyword(s):  
Milk Yield ◽  
Lactation Period ◽  
Mass Ratio ◽  
Black And White ◽  
Protein Mass ◽  
Study Results ◽  
Udmurt Republic ◽  
Basic Standards ◽  
Economic Use ◽  
Fat Mass Ratio

The influence of the age at the first fruitful insemination on the productive longevity of the blackand-white and Kholmogory cows in Udmurt republic was analysed. The study results are presented in the paper. The economic use period of the study cows did not have statistical differences and lasted 3,42–3,43 lactation periods. Black-and-white cows exceeded Kholmogory cows in the lifetime milk yield (by 3416,5 kg), fat content in milk (by 0,47 %) and milk amount in terms of basic standards (by 6317,7 kg) (P > 0,999). The optimal age for the first insemination of black-and-white cows can be considered 16–17 months, since insemination at the specified age ensures highest longevity in cows (3,85 lactations) and the highest lifetime milk yield indices (21347,8 kg), also expressed in terms of basic standards (27065,6 kg). Too early insemination of the black-and-white cows (up to 15 months) is not recommended, as it results in the decreased lifetime milk yields (up to 15491,4 kg), fat and protein content and shortens the economic use period of the animals up to 3,33 lactation periods. The lowest longevity (3,07 lactation periods) was observed in the black-and-white cows inseminated at the age of more than 20 months. The Kholmogory cows demonstrated an increase in lifetime milk yields (1084,5 kg (P > 0,95)) and the economic use period (1,05 lactation period (P > 0,999)) when the age of the first insemination was increased. However, as the fat mass ratio in milk decreased (by 0,06 % (P > 0,999)) and the protein mass ratio in milk fell (by 0,02 % (P > 0,999)), the increase in lifetime milk yield in terms of basic standards resulted from the increase in the age of the first insemination has no significant differences.

The Imaging of Crystal Structures and Crystal Defects

1978 ◽  
Vol 36 (3) ◽  
pp. 207-217
Author(s):  
J.M. Cowley
Keyword(s):  
Electron Microscope ◽  
Crystal Structures ◽  
Phase Contrast ◽  
Crystal Defects ◽  
Atom Density ◽  
Lack Of Information ◽  
Spatial Frequencies

The problem of "understandinq" electron microscope imaqes becomes more acute as the resolution is improved. The naive interpretation of an imaqe as representinq the projection of an atom density becomes less and less appropriate. We are increasinqly forced to face the complexities of coherent imaqinq of what are essentially phase objects. Most electron microscopists are now aware that, for very thin weakly scatterinq objects such as thin unstained bioloqical specimens, hiqh resolution imaqes are best obtained near the optimum defocus, as prescribed by Scherzer, where the phase contrast imaqe qives a qood representation of the projected potential, apart from a lack of information on the lower spatial frequencies. But phase contrast imaqinq is never simple except in idealized limitinq cases.

Sign in / Sign up

Export Citation Format

Share Document