Maximizing efficiency of rumen microbial protein production.

Rumen microbes produce cellular protein inefficiently partly because they do not direct all ATP toward growth. They direct some ATP toward maintenance functions, as long-recognized, but they also direct ATP toward reserve carbohydrate synthesis and energy spilling (futile cycles that dissipate heat). Rumen microbes expend ATP by vacillating between (1) accumulation of reserve carbohydrate after feeding (during carbohydrate excess) and (2) mobilization of that carbohydrate thereafter (during carbohydrate limitation). Protozoa account for most accumulation of reserve carbohydrate, and in competition experiments, protozoa accumulated nearly 35-fold more reserve carbohydrate than bacteria. Some pure cultures of bacteria spill energy, but only recently have mixed rumen communities been recognized as capable of the same. When these communities were dosed glucose in vitro, energy spilling could account for nearly 40% of heat production. We suspect that cycling of glycogen (a major reserve carbohydrate) is a major mechanism of spilling; such cycling has already been observed in single-species cultures of protozoa and bacteria. Interconversions of short-chain fatty acids (SCFA) may also expend ATP and depress efficiency of microbial protein production. These interconversions may involve extensive cycling of intermediates, such as cycling of acetate during butyrate production in certain butyrivibrios. We speculate this cycling may expend ATP directly or indirectly. By further quantifying the impact of reserve carbohydrate accumulation, energy spilling, and SCFA interconversions on growth efficiency, we can improve prediction of microbial protein production and guide efforts to improve efficiency of microbial protein production in the rumen

Protein-carbohydrate interactions during fertilization

Interaction between gametes during fertilization is at least in part regulated by carbohydrate moieties of the zona pellucida (ZP) and carbohydrate binding proteins of the sperm surface. This review focuses on the protein-carbohydrate interactions during the primary binding of the sperm to the ZP in different species. Synthesis, structure and composition of the ZP an summarized. The functional significance of carbohydrate residues of the ZP as sperm receptor is discussed. Sperm surface proteins known to have specific ZP and carbohydrate-binding sites including the mouse beta 1,4-galactosyltransferase and sp56, the rabbit protein Sp17, a human mannose-binding protein and several members of the sperm-adhesin family are presented

Dietary carbohydrate requirement of Heterobranchus longifilis

The dietary carbohydrate requirement of Heterobranchus longifilis was evaluated in two separate experiments.In the first experiment, varying levels of carbohydrate ranging from 28, 24 to58 72% were fed to the fish of mean weight 1.83~c0.02g. Results revealed that the polynomial regression curve for the mean weight gain and the carbohydrate levels did not present a point where Y-max is equal to X-max and so the requirement was not obtained. The second experiment was therefore, conducted with lower levels of carbohydrate ranging from 17.00 to 20.86% and fed to fish with mean weight 0.49~c0.02g. Based on growth and feed efficiency data the carbohydrate requirement was determined to be 19.5

Effects of Diet Composition and Insulin Resistance Status on Plasma Lipid Levels in a Weight Loss Intervention in Women.

BackgroundOptimal macronutrient distribution of weight loss diets has not been established. The distribution of energy from carbohydrate and fat has been observed to promote differential plasma lipid responses in previous weight loss studies, and insulin resistance status may interact with diet composition and affect weight loss and lipid responses.Methods and resultsOverweight and obese women (n=245) were enrolled in a 1-year behavioral weight loss intervention and randomly assigned to 1 of 3 study groups: a lower fat (20% energy), higher carbohydrate (65% energy) diet; a lower carbohydrate (45% energy), higher fat (35% energy) diet; or a walnut-rich, higher fat (35% energy), lower carbohydrate (45% energy) diet. Blood samples and data available from 213 women at baseline and at 6 months were the focus of this analysis. Triglycerides, total cholesterol, and high- and low-density lipoprotein cholesterol were quantified and compared between and within groups. Triglycerides decreased in all study arms at 6 months (P<0.05). The walnut-rich diet increased high-density lipoprotein cholesterol more than either the lower fat or lower carbohydrate diet (P<0.05). The walnut-rich diet also reduced low-density lipoprotein cholesterol in insulin-sensitive women, whereas the lower fat diet reduced both total cholesterol and high-density lipoprotein cholesterol in insulin-sensitive women (P<0.05). Insulin sensitivity and C-reactive protein levels also improved.ConclusionsWeight loss was similar across the diet groups, although insulin-sensitive women lost more weight with a lower fat, higher carbohydrate diet versus a higher fat, lower carbohydrate diet. The walnut-rich, higher fat diet resulted in the most favorable changes in lipid levels.Clinical trial registrationURL: http://www.clinicaltrials.gov. Unique identifier: NCT01424007

Mutational analysis of the carbohydrate binding activity of the tobacco lectin

At present the three-dimensional structure of the tobacco lectin, further referred to as Nictaba, and its carbohydrate-binding site are unresolved. In this paper, we propose a three-dimensional model for the Nictaba domain based on the homology between Nictaba and the carbohydrate-binding module 22 of Clostridium thermocellum Xyn10B. The suggested model nicely fits with results from circular dichroism experiments, indicating that Nictaba consists mainly of beta-sheet. In addition, the previously identified nuclear localization signal is located at the top of the protein as a part of a protruding loop. Judging from this model and sequence alignments with closely related proteins, conserved glutamic acid and tryptophan residues in the Nictaba sequence were selected for mutational analysis. The mutant DNA sequences as well as the original Nictaba sequence have been expressed in Pichia pastoris and the recombinant proteins were purified from the culture medium. Subsequently, the recombinant proteins were characterized and their carbohydrate binding properties analyzed with glycan array technology. It was shown that mutation of glutamic acid residues in the C-terminal half of the protein did not alter the carbohydrate-binding activity of the lectin. In contrast, mutation of tryptophan residues in the N-terminal half of the Nictaba domain resulted in a complete loss of carbohydrate binding activity. These results suggest that tryptophan residues play an important role in the carbohydrate binding site of Nictaba

Carbohydrate supplementation and prolonged intermittent, high-intensity exercise in adolescents: research findings, ethical issues and suggestions for the future

In the last decade, research has begun to investigate the efficacy of carbohydrate supplementation for improving aspects of physical capacity and skill performance during sport-specific exercise in adolescent team games players. This research remains in its infancy, and further study would be beneficial considering the large youth population actively involved in team games. Literature on the influence of carbohydrate supplementation on skill performance is scarce, limited to shooting accuracy in adolescent basketball players and conflicting in its findings. Between-study differences in the exercise protocol, volume of fluid and carbohydrate consumed, use of prior fatiguing exercise and timing of skill tests may contribute to the different findings. Conversely, initial data supports carbohydrate supplementation in solution and gel form for improving intermittent endurance running capacity following soccer-specific shuttle running. These studies produced reliable data, but were subject to limitations including lack of quantification of the metabolic response of participants, limited generalization of data due to narrow participant age and maturation ranges, use of males and females within the same sample and non-standardized pre-exercise nutritional status between participants. There is a lack of consensus regarding the influence of frequently consuming carbohydrate-containing products on tooth enamel erosion and the development of obesity or being overweight in adolescent athletes and non-athletes. These discrepancies mean that the initiation or exacerbation of health issues due to frequent consumption of carbohydrate-containing products by adolescents cannot be conclusively refuted. Coupled with the knowledge that consuming a natural, high-carbohydrate diet ∼3–8 hours before exercise can significantly alter substrate use and improve exercise performance in adults, a moral and ethical concern is raised regarding the direction of future research in order to further knowledge while safeguarding the health and well-being of young participants. It could be deemed unethical to continue study into carbohydrate supplementation while ignoring the potential health concerns and the possibility of generating similar performance enhancements using natural dietary interventions. Therefore, future work should investigate the influence of pre-exercise dietary intake on the prolonged intermittent, high-intensity exercise performance of adolescents. This would enable quantification of whether pre-exercise nutrition can modulate exercise performance and, if so, the optimum dietary composition to achieve this. Research could then combine this knowledge with ingestion of carbohydrate-containing products during exercise to facilitate ethical and healthy nutritional guidelines for enhancing the exercise performance of adolescents. This article addresses the available evidence regarding carbohydrate supplementation and prolonged intermittent, high-intensity exercise in adolescent team games players. It discusses the potential health concerns associated with the frequent use of carbohydrate-containing products by adolescents and how this affects the research ethics of the field, and considers directions for future work

Consumer Willingness to Pay for Breads Marketed as "Low-Carbohydrate"

Bread producers are taking advantage of healthy feeding habits by developing new "low carbohydrate" products to entice customers. These low carbohydrate breads are generally more expensive than conventional types. This study tests the hypothesis that consumers are willing to pay higher premium for "low carbohydrate" breads at various locations and markets. We use retail data in a hedonic pricing framework to estimate the premium paid for the "low carbohydrate" attribute of bread. Results show that the implicit price of the "low carbohydrate" attribute of bread ranges from about 0.06¢ to 1.1¢ per gram, reflecting the amount consumers are willing to pay above the price of conventional bread.low carbohydrate bread, hedonic price, willingness to pay, Institutional and Behavioral Economics, D12,

The biofilm matrix of Pseudomonas sp. OX1 grown on phenol is mainly constituted by alginate oligosaccharides

The structure of the major constituent of the biofilm matrix produced by Pseudomonas sp. OX1, when grown on phenol as the sole carbon source is described. This investigation, carried out by chemical analysis, NMR spectroscopy and MALDI-TOF MS spectrometry, showed the presence of an oligosaccharide blend with the typical alginate structure, namely (1-->4) substituted beta-D-mannuronic (ManA) and alpha-L-guluronic acid (GulA). GulA residues were non-acetylated whereas ManA was always O-acetylated at C-2 or C-3

Glycolytic enzymes - novel carbohydrate binding proteins for glycoprotein analysis

•The cloning, expression, purification and characterisation of recombinant prokaryotic glycolytic enzymes •The mutagenesis of prokaryotic glycolytic enzymes to generate novel recombinant carbohydrate binding proteins •The characterisation of the binding profile of the novel recombinant carbohydrate binding protein

Does the inclusion of moderate amounts of red meat in the diet of exercising older women impact on faecal markers of bowel health, including faecal lactoferrin?

Background: High intakes of red meat may be associated with increased risk of colorectal cancer (CRC), however, to determine CRC risk, it is important to assess faecal changes related to protein and carbohydrate metabolism.Objective: To determine the influence of three weekly meals rich in red meat as opposed to a carbohydrate control diet on faecal markers which are involved in the aetiology of CRC.Design: Twenty post-menopausal women (aged 60-75) undertook, 3 times a week for 12 weeks, a 30 minute exercise session followed immediately by a cooked meal that was high in lean red meat, low in carbohydrate (n= 10) or low in lean red meat, high in carbohydrate (n=10). Dietary fibre intake and macronutrients were kept constant. At the beginning and end of the study, three-day faecal samples were collected and by-products of protein fermentation and carbohydrate metabolism, undigested fibre residues, and faecal output and colonic bacterial microbiota changes measured.Outcomes: No significant differences were observed in subjects on either diet when comparing faecal output, faecal pH, other faecal markers, nor faecal lactoferrin. There was a trend observed in changes in the population of colonic microbiota using FISH analysis. Bacteroides spp. and Prevotella spp. appeared to decrease in women consuming a high red meat diet compared with an increase in women consuming a high carbohydrate diet.Conclusions: In this pilot study the trend in colonic microbiota change is interesting and suggests that dietary influence of colonic microbiota, especially changes in Bacteroidetes, may be indicative of risk of gut damage and disease compared to other faecal markers.<br /