Improved methods for mutacin detection and production

Studies of mutacins have always been hampered by the difficulties in obtaining active liquid preparations of these substances. In order to be commercially produced, good mutacin yields have to be obtained, preferably in inexpensive media. The results presented here indicate that mutacins can be produced in supplemented cheese whey permeate. The influence of carbon and nitrogen supplements on mutacin production varied according to the producer strain. The use of CaCO3 as a buffer in batch cultures resulted in improved yields of mutacin in the supernatants. Antimicrobial activity assays were improve by acidification of the diluent (pH 2) and were less variable in peptone water (0.5%). The culture medium consisting of cheese whey permeate (6% w/v), yeast extract (2% w/v) and CaCO3 (1% w/v) was found to be an inexpensive medium for the efficient production of mutacins.     

Effects of different dietary carbohydrates on hepatic enzymes of copper-deficient rats

The present study was undertaken to measure the activities of several hepatic enzymes of regulatory importance in the pathways of lipogenesis and gluconeogenesis in rats fed diets marginally deficient in copper (1.2 micrograms Cu/g of diet) and containing either fructose, glucose, or starch as the carbohydrate sources. Although all copper-deficient rats exhibited the characteristic signs of copper deficiency, they were more pronounced in rats fed the diet containing fructose. Except for the activity of phosphoenolpyruvate carboxykinase which was unaffected either by copper deficiency or by the type of dietary carbohydrate, the hepatic activities of glucose-6-phosphate dehydrogenase, malic enzyme, L-alpha-glycerophosphate dehydrogenase and fructose 1,6-diphosphatase were unaffected by copper deficiency but were affected by the type of carbohydrate in the diet. Fructose produced the greatest increase in enzymatic activities, whereas starch produced the least activity and glucose induced an intermediate effect. These results indicate that the deleterious effects of a fructose diet deficient in copper on biochemical and physiological indices could not be due to an immediate metabolite of fructose. However, the involvement of a subsequent metabolite of fructose in the mechanism of copper utilization and/or requirement cannot be excluded.     

Effects of dietary carbohydrates and temperatures on slow growing juvenile eels Anguilla anguilla

Synopsis The influence of the level of carbohydrate in a purified diet on the growth of slow-growing Anguilla anguilla maintained at different temperatures was examined. The average weight increase of eels maintained at temperatures of 25° or 27° C and fed a diet containing 20% or 30% glucose, was significantly higher than the mean weight increase of eels maintained at the same temperature but fed a diet containing soluble corn starch, at the same percentages. There was no significant difference in the mean weight of slow growing eels fed 10%, 20% and 30% soluble corn starch or 10% glucose. There was no significant difference in protein content (wet weight) among the experimental groups. However, elvers that were fed a high percentage of carbohydrates (glucose or starch) and maintained at 27° C had a higher percentage of lipids in body weight compared with the other experimental groups.     

变链素活性与变形链球菌基因多态性的关系研究

目的探讨变链素的活性与变形链球菌(MS)基因多态性的关系。方法在AP-PCR基因分型的基础上,选择来自单基因型定植的个体50株MS为单基因型组,另50株来自多基因型共同定植的个体为多基因型组,用平板法检测2组菌株产生变链素对10个指示株的抑制情况,T-检验比较2组菌株抑菌环和抑菌谱的均数差异。结果所有的实验株(100%)均可产生抑制6~8个指示株的变链素,抑菌环和抑菌谱在不同个体之间变异,组间均数的比较不具有显著性(P值分别是0.12,1.79)。结论多基因型MS定植的口腔,在产生变链素方面似乎不具有优势。     

Optimization of the production of the lantibiotic mutacin 1140 in minimal media

Mutacin 1140 is produced by Streptococcus mutans and belongs to the type A lantibiotic family. Experiments were done to optimize production of mutacin 1140 in minimal media enabling a more cost efficient downstream purification method. The development of a small volume fermentation method enabled a rapid screen of several variables in a standard shaking incubator. This method provided a fast approach for determining components that promote mutacin 1140 production in minimal media broth. Lactose was determined to be the optimal carbon source for mutacin 1140 production. High concentrations of CaCl₂ (0.3%, w/v) and MgSO₄ (0.77%, w/v) promoted an increase in mutacin 1140 production, while ZnCl₂ and FeCl₃ appeared to impair production. Optimization of mutacin 1140 production in minimal media resulted in more than a 100-fold increase in production compared to the base medium used to begin our optimizations. The yield has been estimated by RP-HPLC to be ∼10 mg/L.     

鱼类对糖的利用评述

一般认为鱼类对糖的利用能力低下[1],鱼类被视为具有先天性的“糖尿病体质”[2]。糖(没有特别说明时本文指可消化糖)是最廉价的饲料能源,因此,鱼类营养研究领域的一个重要话题便是如何提高对饲料糖的利用。近20年来,关于鱼类糖营养的研究比较活跃,在糖的生理功能、鱼类对饲料糖的利用特点、影响因素和需求量等方面都取得了一定的突破。回顾前人的工作,结合最新研究成果,作者发现在关于鱼类对糖的利用能力大小这一问题上有重新认识的必要。现就这一领域的研究方法和研究成果作一评述。1糖的生理功能糖类按其生理功能可分为可消化糖类(或称无…     

Effect of dietary proteins and carbohydrates on urinary and sympathoadrenal catecholamines

We previously observed that administration of tyrosine to rats or humans elevated urinary dopamine, norepinephrine and epinephrine levels. The present studies examine the effects on these urinary catecholamines of varying the ratio of protein to carbohydrate in the diets.Rats consumed diets containing 0, 18 or 40% protein (76, 58 and 36% carbohydrate respectively) for 8 days. The stress of consuming the protein-free food was associated with a 16% weight reduction, and with significantly lower serum, heart and brain tyrosine levels than those noted in rats eating the 18 or 40% protein diets. Absence of protein from the diet also decreased urinary levels of dopamine and DOPA but increased urinary norepinephrine and epinephrine, probably by increasing sympathoadrenal discharge; it also increased the excretion of DOPA in animals pretreated with carbidopa, a DOPA decarboxylase inhibitor. Carbidopa administration decreased urinary dopamine, norepinephrine and epinephrine as expected; however, among carbidopa-treated rats urinary norepinephrine and epinephrine concentrations were highest for animals consuming the protein-free diet, again suggesting enhanced release of stored catecholamines from sympathoadrenal cells. The changes in urinary catecholamines observed in animals eating the protein-free diet were similar to those seen in rats fasted for 5 days: dopamine levels fell sharply while norepinephrine and epinephrine increased.These data indicate that the effects of varying dietary protein and carbohydrate contents on dopamine secretion from peripheral structures differ from its effects on structures secreting the other two catecholamines. Protein consumption increases dopamine synthesis and release probably by making more of its precursor, tyrosine, available to peripheral dopamine-producing cells; it decreases urinary norepinephrine and epinephrine compared with that seen in protein-deprived animals, probably by diminishing the firing of sympathetic neurons and adrenal chromaffin cells.     

Effects of a late supper on digestion and the absorption of dietary carbohydrates in the following morning

Background

Our previous experiment showed that the light intensity exposed on the subjects during evening time had no effect in the following morning on the efficiency of the digestion and absorption of dietary carbohydrates ingested at a usual suppertime. People who keep late hours usually have a late suppertime; thus, we examined the effects of a late suppertime on gastrointestinal activity in the following morning in comparison to that of a usual suppertime.

Methods

Twelve female university students volunteered as paid participants. The breath hydrogen test was carried out to estimate the amount of unabsorbed dietary carbohydrates and the percentage of the total amount of dietary carbohydrates in the breakfast that were unabsorbed, as well as to estimate oro-cecal transit time. The respiratory quotient was also measured to find the ratio of carbohydrates/lipid metabolism in the post-breakfast state. Subjects’ peripheral blood glucose concentration was measured by a blood glucose meter. The subjects participated under two different experimental conditions: with a usual suppertime (having supper at 18:00) and a late suppertime (having supper at 23:00).

Results

The efficiency of the digestion and absorption of dietary carbohydrates in the breakfast under late suppertime conditions was higher than that under usual suppertime conditions. Usual or late suppertime had no effect on the ratio of carbohydrates to lipids oxidized after the subjects had breakfast. There were significant differences in the blood glucose level between the two conditions at 30, 60, 120, 150, and 180 minutes after having breakfast, whereas the mean blood glucose level under late suppertime conditions was significantly higher than under usual suppertime conditions.

Conclusions

Having a late supper showed a worse effect on postprandial serum glucose profiles the following morning. This study confirmed that keeping our usual meal timing is important for our health.     

Steroidal regulation of hydrolyzing activity of the dietary carbohydrates in the silkworm, Bombyx mori

Blood sugar is an essential energy source for growth and development and is maintained at a constant level through precise regulation of formation and utilization. Sugars are produced from dietary carbohydrates by enzymatic hydrolysis in the digestive tract, which are under the homeostatic control of paracrine and prandial mechanisms in mammals. Here, we show that dietary carbohydrates hydrolyzing activity of the digestive tract is developmentally regulated by the steroid hormone ecdysone in the silkworm, Bombyx mori. The dietary carbohydrates hydrolyzing activity remained high throughout the last larval period and then decreased to negligible levels until the pupal period. However, dietary carbohydrates digestive activities were constitutively high when the steroidogenic organ, prothoracic glands were ablated. The prothoracic glands produced and released a large amount of ecdysone at the end of the larval period, suggesting that ecdysone is responsible for the decrease in dietary carbohydrates hydrolyzing activity. In fact, ecdysone decreased the activity to negligible levels in silkworms lacking the prothoracic glands. The present results indicate that the dietary carbohydrates hydrolyzing activity is regulated by ecdysone and that an increase in ecdysone titer decreases that activity at the end of the larval period, suggesting that ecdysone is essential for metabolic coordination during development.     

Effect of dietary carbohydrates and copper status on blood pressure of rats

Copper deficiency was induced in rats by feeding diets containing either 62% starch, fructose or glucose deficient in copper for 6 weeks. All copper deficient rats, regardless of the dietary carbohydrate, exhibited decreased ceruloplasmin activity and decreased serum copper concentrations. Rats fed the fructose diet exhibited a more severe copper deficiency as compared to rats fed either starch or glucose. The increased severity of the deficiency was characterized by reduced body weight, serum copper concentration and hematocrit. In all rats fed the copper adequate diets, blood pressure was unaffected by the type of dietary carbohydrate. Significantly reduced systolic blood pressure was evident only in rats fed the fructose diet deficient in copper. When comparing the three carbohydrate diets, the physiological and biochemical lesions induced by copper deprivation could be magnified by feeding fructose.     

Glycaemic and insulinemic response to dietary carbohydrates in horses

Background

Dietary sugar and starch affect plasma glucose and insulin concentrations. Little information is available about the effect of dietary fibre on plasma glucose and insulin concentration. It is hypothesized that different dietary fibre compositions will alter post-prandial glycaemic- and insulinemic index of test meals. The objective was to measure postprandial glucose and insulin concentrations in horses fed meals of different fibre compositions.

Methods

Blood was drawn via jugular vein puncture and the glycaemic and insulinemic index were calculated.

Results

The meal effect on glycaemic and insulinemic response followed the expected pattern, where plasma concentrations increased after feeding and declined after peak concentration. Glycaemic index was 100 (H), 102 (OB), 102 (BB) and 106 (M) and did not differ significantly between meals. Insulinemic index was 100 (H), 140 (OB), 121 (BB) and 125 (M) and did not differ significantly between meals.

Conclusions

In conclusion, meals containing different fibre compositions did not affect the glycaemic- and insulinemic index in horses.

     

Effects of dietary changes on muricide activity in adult and young rats

Recent works have showed different interrelations between dietary tryptophan intake and aggressive behaviour in different groups of rats. In this experiment the AA. have treated thirty Sprague-Dawley rats (15 youngs and 15 adults) with tryptophan free-diet, during eight weeks. Muricide activity was weekly controlled; daily food intake for all group was recorded. Young rats feeding tryptophan free-diet and young rats pairfed controls showed aggressive behaviour at the sixth week of treatment. Adult rats did not show any changes of mouse killing during the whole period of experiment.     

Microalgae-based carbohydrates for biofuel production

Microalgae are considered as the most promising renewable feedstock for biofuel production and biorefineries, due to their advantages of fast growth, efficient carbon dioxide fixation, not competing for arable lands and potable water, and potentially accumulating high amounts of lipids and carbohydrates. Since carbohydrates in microalgae biomass are mainly cellulose in the cell wall and starch in the plastids without lignin and low hemicelluloses contents, they can be readily converted into fermentable sugars. However, to date there are very few studies focusing on the use of microalgae-based carbohydrates for biofuel production, which requires more understanding and knowledge to support the technical feasibility of this next-generation feedstock. This review article elucidates comprehensive information on the characteristics and metabolism of main fermentable microalgal carbohydrates (e.g., starch and cellulose), as well as the key factors and challenges that should be addressed during production and saccharification of microalgal carbohydrates. Furthermore, developments on the utilization of microalgae-based feedstock in producing liquid and gaseous biofuels are summarized. The objective of this article is to provide useful knowledge and information with regard to biochemistry, bioprocess engineering, and commercial applications to assist in the viable technology development of for biofuels generation from microalgae-based carbohydrates.     

Effects of carbohydrates on the pharmacokinetics and biological activity of equine chorionic gonadotropin in vivo.

The sialylation of eCG was examined to determine its influence on the in vivo metabolism and biological activity of the molecule. Sialic acid was decrementally removed from eCG by incubation with agarose-linked neuraminidase for varying time periods. Pharmacokinetic parameters for the disappearance of 4,000 IU (267 micrograms) of three desialylated eCG preparations (20%, 53%, and 80% sialic acid removed) and control eCG were determined in sheep. The clearance rate of eCG increased (p less than 0.05) with each decrement of sialic acid. The removal of 53% sialic acid enhanced the distribution of eCG into the tissues, compared to control and 20% desialylated eCG (p less than 0.05), presumably because of increased lipid solubility and decreased molecular size. Desialylation to 53% did not alter the elimination half-life of eCG. The removal of 80% sialic acid resulted in the disappearance of eCG from the serum within 1 h, whereas control eCG was still present at 120 h. In vivo trials in rats disclosed that the control eCG preparation increased ovulatory rate at doses of 10-100 IU and ovarian weight at doses of 10-300 IU relative to saline-treated rats (p less than 0.01). The 20% desialylated eCG induced superovulatory and ovarian weight responses, but 100-500 IU were required to achieve the same result as that produced by control eCG. The 53% and 80% desialylated eCG preparations induced a mild superovulatory response (p less than 0.01) but no ovarian weight response. It was concluded that sialic acid was significant to the distribution and disappearance of eCG. The effects of carbohydrate removal on biological activity (e.g., superovulation) are primarily a function of clearance rate rather than tissue-specific phenomena.     

Effect of dietary carbohydrates on bacterial cholyltaurine hydrolase in poultry intestinal homogenates

The bile salt hydrolase activity in intestinal homogenates reflects composite activities of the gastrointestinal microbial consortia. We have proposed that specific transformations of conjugated bile acids by the intestinal microflora result in the production of metabolites which depress the growth of poultry. The influence of dietary carbohydrates on the physical and kinetic properties of cholyltaurine hydrolase activity, one such bile acid-transforming enzyme in gastrointestinal homogenates of young chickens, was characterized by using a sensitive radiochemical assay. Cholyltaurine hydrolase activity in crude extracts of ileal homogenates was increased twofold by 0.25% Triton X-100 and a freeze-thaw cycle. The pH optimum for cholyltaurine hydrolase from ileal homogenates was very broad and reflected the pH range of poultry intestinal contents (i.e., 5.8 to 6.4). The carbohydrate component of the diet did not affect the apparent temperature optimum (41 degrees C) or stability profile, nor did it affect the apparent Km for taurocholic acid hydrolysis (approximately 0.43 mM). The enzymes in intestinal homogenates were active on all taurine-conjugated bile acids tested. The carbohydrate component of the diet did, however, affect the specific activity of cholyltaurine hydrolase in ileal homogenates from chickens. The levels of cholyltaurine hydrolase activity (rye greater than sucrose greater than corn) in homogenates from birds fed the different diets were directly related to the amount of growth depression (rye greater than sucrose greater than corn) associated with feeding these dietary carbohydrates. These data suggest that intestinal levels of cholyltaurine hydrolase are correlated with the amount of carbohydrate-induced growth depression in poultry.     

Effects of dietary zinc and copper on free radical production in rat lung and liver

The effects of dietary copper and zinc on free radical production in lung and liver microsomes were studied in male weanling rats. The rats were fed for 6 weeks on one of seven diets, with different copper and zinc concentrations representing low, adequate, and high dietary levels of copper and low and adequate levels of zinc. Rats were put on diets arranged in a 3 X 2 factorial design with copper and zinc supplementations of 0, 15, and 500 mg/kg and 0.5 or 100 mg/kg, respectively. The low copper diet depressed copper levels in both the lungs and liver, although zinc levels were unchanged in rats on the low zinc diets. Endogenous carbon-centered lipid radical production in microsomes induced by NADPH was measured using spin-trapping techniques. The low zinc diets increased free radical production in lung microsomes but not in liver microsomes. No change in free radical production was observed in lung or liver microsomes obtained from rats on low copper diets. The data indicate that endogenous free radical production is increased in lung microsomes as a function of dietary zinc deficiency but is not influenced by copper status.     

壳聚糖对肉鸡抗氧化能力及生产性能的作用

为了探讨壳聚糖对家禽肉鸡抗氧化能力及生产性能的作用,采用1日龄黑脚大麻鸡6组各100只进行分组实验,喂食壳聚糖复合剂,测定了肉鸡血清中超氧化物歧化酶（SOD）活力、丙二醛（MDA）含量、谷胱甘肽过氧化物酶（GSH-PX）活力、免疫器官指数、腹脂率和料重比等指标。结果表明：2种分子量的壳聚糖在较低浓度时能显著提高60日龄肉鸡血清中SOD的酶活力（P〈0．05）,但对其他日龄肉鸡血清中SOD酶活力影响不显著;壳聚糖对血清中MDA含量和GSH-PX酶活力影响不显著;实验组的存活率提高,腹脂率和料重比稍有下降。在肉鸡饲养中,壳聚糖是一种潜在的、绿色的抗生素替代品。