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Different Carbohydrates (different + carbohydrate)
Selected AbstractsEffect of finishing diets on Escherichia coli populations and prevalence of enterohaemorrhagic E. coli virulence genes in cattle faecesJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2005R.A. Gilbert Abstract Aim:, To determine the effect of different carbohydrate-based finishing diets on fermentation characteristics and the shedding of Escherichia coli and enterohaemorrhagic E. coli (EHEC) virulence genes in cattle faeces. Methods and Results:, The size of faecal E. coli populations and fermentation characteristics were ascertained in three experiments where cattle were maintained on a range of finishing diets including high grain, roughage, and roughage + molasses (50%) diets. Increased E. coli numbers, decreased pH and enhanced butyrate and lactate fermentation pathways were associated with grain diets, whereas roughage and roughage + molasses diets resulted in decreased concentrations of ehxA, eaeA and stx1 genes, this trend remaining at lairage. In one experiment, faecal E. coli numbers were significantly lower in animals fed roughage and roughage + molasses, than animals fed grain (4·5, 5·2 and 6·3 mean log10 g,1 digesta respectively). In a second experiment, faecal E. coli numbers were 2 log lower in the roughage and roughage + molasses diets compared with grain-fed animals prior to lairage (5·6, 5·5 and 7·9 mean log10 g,1 digesta respectively) this difference increasing to 2·5 log at lairage. Conclusions:, The type of dietary carbohydrate has a significant effect on E. coli numbers and concentration of EHEC virulence genes in faeces of cattle. Significance and Impact of the Study:, The study provides a better understanding of the impact finishing diet and commercial lairage management practices may have on the shedding of E. coli and EHEC virulence factors, thus reducing the risk of carcass contamination by EHEC. [source] Molecular determinants of ligand specificity in family 11 carbohydrate binding modules , an NMR, X-ray crystallography and computational chemistry approachFEBS JOURNAL, Issue 10 2008Aldino Viegas The direct conversion of plant cell wall polysaccharides into soluble sugars is one of the most important reactions on earth, and is performed by certain microorganisms such as Clostridium thermocellum (Ct). These organisms produce extracellular multi-subunit complexes (i.e. cellulosomes) comprising a consortium of enzymes, which contain noncatalytic carbohydrate-binding modules (CBM) that increase the activity of the catalytic module. In the present study, we describe a combined approach by X-ray crystallography, NMR and computational chemistry that aimed to gain further insight into the binding mode of different carbohydrates (cellobiose, cellotetraose and cellohexaose) to the binding pocket of the family 11 CBM. The crystal structure of C. thermocellum CBM11 has been resolved to 1.98 Å in the apo form. Since the structure with a bound substrate could not be obtained, computational studies with cellobiose, cellotetraose and cellohexaose were carried out to determine the molecular recognition of glucose polymers by CtCBM11. These studies revealed a specificity area at the CtCBM11 binding cleft, which is lined with several aspartate residues. In addition, a cluster of aromatic residues was found to be important for guiding and packing of the polysaccharide. The binding cleft of CtCBM11 interacts more strongly with the central glucose units of cellotetraose and cellohexaose, mainly through interactions with the sugar units at positions 2 and 6. This model of binding is supported by saturation transfer difference NMR experiments and linebroadening NMR studies. [source] Fructose and glucose mediates enterotoxin production and anaerobic metabolism of Bacillus cereus ATCC14579TJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2009O. Ouhib-Jacobs Abstract Aims:, To determine the effects of carbohydrates on Bacillus cereus ATCC14579T anaerobic metabolism and enterotoxin production in amino acids rich medium. Methods and Results:,Bacillus cereus anaerobic growth on different carbohydrates (glucose, fructose, sucrose or glucose,fructose mixture) was examined in synthetic mMOD medium under continuous cultures (, = 0·2 h,1). Fermentation end-products, flux partitioning at each key branch points of the mixed acid pathway and consumption or production of amino acids were determined. On both fructose and sucrose, ATP production was favoured via acetate production from acetyl-CoA. In addition, amino acids present in the growth medium showed significant variations with high consumption of serine and net production of glutamate and alanine on some or all sugars. Enterotoxins Hbl and Nhe production was high during growth on fructose (or mixtures involving a fructose moiety). Conclusions:, Fructose was identified as a key sugar influencing anaerobic metabolism and toxin production of B. cereus. Significance and Impact of the Study:, The physiological differences associated with the fermentation of the various carbohydrates clearly modify toxinogenesis indicating that the risk of foodborne pathogens is to some extent dependent upon the prevailing nutritional environment. [source] Influence of carbohydrates on stability of papain in aqueous tetrahydrofuran mixtureJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 1 2009András Szabó Abstract BACKGROUND: The use of enzymes in organic solvents has extended the scale of their practical applications. Papain has been widely used in chemical syntheses because of its broad substrate specificity. The aim of the present study was to improve the stability of papain in aqueous tetrahydrofuran (THF) by using different saccharides. The effects of these carbohydrates on the structure of papain were followed by means of circular dichroism (CD) and fluorescence spectroscopic measurements. RESULTS: In contrast with most organic solvents, 60% (i.e. 600 mL L,1) THF practically inactivated the enzyme within 30 min. Sugars protected papain from THF-induced inactivation in the sequence D -ribose > D -fructose > D -glucose > D -saccharose > D -raffinose. Ribose at 1.6 mol L,1 proved the most effective stabiliser: in 60% THF in the presence of ribose, papain preserved about 55% of its initial activity after 2 h. Fluorescence and near-UV CD spectroscopic measurements revealed local changes in the papain conformation. With decrease in the free amino group content of the enzyme, protein-carbohydrate interactions (Schiff base formation) were detected. CONCLUSION: These results demonstrate that the catalytic activity and stability of papain may be increased in aqueous THF by using different carbohydrates, when a more compact structure of the enzyme is formed. Copyright © 2008 Society of Chemical Industry [source] Modeling solubilities of sugars in alcohols based on original experimental dataAICHE JOURNAL, Issue 9 2007Fernando Montañés Abstract Solubility of six different carbohydrates in methanol, ethanol, 1-propanol, and 2-propanol were measured at 22, 30, and 40°C. Ketose sugars (fructose, tagatose, and lactulose) show higher solubilities than aldoses (glucose, galactose, and lactose). The binary solid,liquid equilibrium data obtained was satisfactory represented by using the A-UNIFAC model. Additionally, the capability of the model to predict the carbohydrate solubility in alcohol,alcohol and alcohol,water mixed solvents was explored. © 2007 American Institute of Chemical Engineers AIChE J, 2007 [source] Rapid Screening of Lectins for Multivalency Effects with a Glycodendrimer MicroarrayCHEMBIOCHEM, Issue 13 2010Núria Parera Pera Dr. Abstract Multivalency is an important phenomenon in protein,carbohydrate interactions. In order to evaluate glycodendrimers as multivalent inhibitors of carbohydrate binding proteins, we displayed them on a microarray surface. Valencies were varied from 1 to 8, and corrections were made for the valencies so that all surfaces contained the same amount of the sugar ligand. Five different carbohydrates were attached to the dendrimers. A series of fluorescent lectins was evaluated, and for each of them a binding profile was obtained from a single experiment showing both the specificity of the lectin for a certain sugar and whether it prefers multivalent ligands or not. Very distinct binding patterns were seen for the various lectins. The results were rationalized with respect to the interbinding distances of the lectins. [source] | ||||||||||