甲壳低聚糖抑菌性能鉴定

甲壳低聚糖对日常生活中特别是食品中一些常见的细菌、霉菌、酵母菌具有抑菌作用,其抑菌率明显超过对照组,相应最小抑菌质量浓度为1-10g/L,随着甲壳低聚糖质量浓度的增加,抑菌作用逐渐变强。该文还探讨了甲壳低聚糖抑菌活性与溶解性之间的关系,结果表明甲壳低聚糖的抑菌活性与氨基质子化有关。     

甲壳低聚糖铁穴Ⅲ雪、硒配合物的制备及其表征

以甲壳低聚糖与FeCl3反应络合成甲壳低聚糖铁(Ⅲ),以甲壳低聚糖与亚硒酸反应络合成甲壳低聚糖硒,对2种络合物的稳定性及紫外、红外光谱进行检测。甲壳低聚糖铁(Ⅲ)水溶液中不存在游离铁(Ⅲ),表明铁(Ⅲ)与甲壳低聚糖形成了稳定的配合物,在pH值为3～11的范围内不水解,无沉淀产生;甲壳低聚糖硒水溶液中不存在游离的硒离子,表明硒元素与甲壳低聚糖也形成了稳定的配合物。红外光谱扫描也表明甲壳低聚糖与铁、硒络合的特征峰变化。研究结果说明甲壳低聚糖与铁(Ⅲ)或硒能形成稳定的配合物。经红外光谱分析其配位的基团主要是氨基,羟基也有一定的配位能力,但是强度低于氨基。以上实验结果有望使甲壳低聚糖铁(Ⅲ)配合物成为一种具有较好生物利用度的营养型补铁剂,使甲壳低聚糖硒配合物成为具有多功能的保健药品。     

甲壳低聚糖的微生态学效应

目的 :了解甲壳低聚糖的微生态学效应 ,为其开发为微生态调节剂提供实验依据。方法 :用甲壳低聚糖〔6 0 0 m g/ (kg· d)〕给正常小鼠、肠道脱污染模型小鼠及 STZ糖尿病模型小鼠连续灌胃 7d及 2 1d,用添加 0 .3%甲壳低聚糖的高脂饲料为高血脂症大鼠模型连续灌胃 4 2 d。各空白对照组均用等体积无菌盐水灌胃。而后分析各组动物肠菌群 ,并测定 STZ糖尿病小鼠血糖、高血脂症大鼠 TC及 HDL- C值。结果 :甲壳低聚糖可以优化正常小鼠肠菌群 ,双歧杆菌数较空白对照组明显增多 (P<0 .0 5 ) ,B/ E值为对照组19.3倍 ,可纠正实验动物因肠道脱污染、糖尿病及高血脂症所致的肠菌群失调 ,双歧杆菌或乳杆菌相应增加 ,与相应空白对照组比较 ,其差异均有显著性意义 ,可以明显降低糖尿病小鼠血糖及高血脂症大鼠血清TC值。结论 :甲壳低聚糖具有良好的微生态学效应 ,可作为微生态调节剂开发应用     

酶法合成功能性低聚糖

功能性低聚糖具有无毒、无残留、稳定性强等特点,作为新型绿色添加剂被广泛应用在食品、饲料、医药行业。国际市场上10余种低聚糖产品中除大豆低聚糖、棉籽糖外,主要采用酶法制备。用于合成功能性低聚糖的酶包括糖苷酶、糖基转移酶和磷酸化酶。本文综述了功能性低聚糖种类、性质和制备方法,分析了酶法合成低聚糖的优缺点,阐述了磷酸化酶种类、催化特性和低聚糖产物。多酶法合成策略和目标酶的分子改造将是酶法合成功能性低聚糖的发展方向。     

魔芋葡甘露低聚糖的酶法制备工艺的初步研究

利用β-甘露聚糖酶产品水解魔芋胶制备魔芋葡甘露低聚糖的工艺条件。在加样顺序、pH、酶添加量、时间、温度等单因素试验的基础上,进一步通过正交试验确定的最佳工艺条件为:魔芋胶浓度10g/L,酶添加量为100U/g,pH5.5,45℃条件下,酶解时间1.5h。再利用酵母发酵去除可发酵性糖的方法,以获得最终产物为100%的魔芋葡甘露低聚糖。     

甲壳低聚糖铁(Ⅲ)、硒配合物的制备及其表征

以甲壳低聚糖与FeCl3反应络合成甲壳低聚糖铁(Ⅲ),以甲壳低聚糖与亚硒酸反应络合成甲壳低聚糖硒,对2种络合物的稳定性及紫外、红外光谱进行检测。甲壳低聚糖铁(Ⅲ)水溶液中不存在游离铁(Ⅲ),表明铁(Ⅲ)与甲壳低聚糖形成了稳定的配合物,在pH值为3-11的范围内不水解,无沉淀产生;甲壳低聚糖硒水溶液中不存在游离的硒离子,表明硒元素与甲壳低聚糖也形成了稳定的配合物。红外光谱扫描也表明甲壳低聚糖与铁、硒络合的特征峰变化。研究结果说明甲壳低聚糖与铁(Ⅲ)或硒能形成稳定的配合物。经红外光谱分析其配位的基团主要是氨基,羟基也有一定的配位能力,但是强度低于氨基。以上实验结果有望使甲壳低聚糖铁(Ⅲ)配合物成为一种具有较好生物利用度的营养型补铁剂,使甲壳低聚糖硒配合物成为具有多功能的保健药品。     

酶法制备功能性纤维低聚糖的研究

研究里氏木霉(Trichoderma reesei)Rut C30纤维素酶单一组分EGI、EGII和CBHI降解纤维素的机理及纤维低聚糖酶法制备技术,进而初步研究纤维低聚糖对青春双歧杆菌的增殖作用。以内切葡聚糖酶EGII酶法制备纤维低聚糖,每克纤维素最佳酶用量1 U,最佳酶解时间90 min,制备得到的纤维低聚糖中纤维二糖、纤维三糖和纤维四糖占总糖的比例分别为43.8%、34.8%和7.9%。以纤维二糖、纤维低聚糖为C源增殖青春双歧杆菌,菌体质量浓度增殖倍数分别为2.14、2.84。     

壳低聚糖的制备与应用

壳低聚糖 (ｃｈｉｔｏｏｌｉｇｏｓａｃｃｈａｒｉｄｅｓ)是一类由Ｎ 氨基葡萄糖通过 β 1,4糖苷键连接的低聚合度糖类。这种低聚糖既可生物合成 ,也可以由壳聚糖降解获得。壳低聚糖有良好的水溶性 ,容易被机体吸收利用。壳聚糖是最大量的自然资源之一 ,对它已有广泛深入的研究。但对壳低聚糖的研究则罕见报道 ,亟待开发 ,尽管目前已有保健食品、高级化妆品、抗癌药物、植物生长调节剂等多种专利产品问世。1.壳低聚糖的制备1.1　酸降解法　　目前已知能用于降解壳聚糖的酸有ＨＣｌ、Ｈ2 ＳＯ4 、ＨＮＯ2 、ＨＦ等。Ｈｏｒｏｗｉｔｚ等用 3.3…     

甲壳酶特性与应用研究

本文阐明了甲壳酶(甲壳素酶和壳聚糖酶)的物理化学酶学性质,并着重对甲壳酶的结构、催化机制和其多方面应用进行了论述,同时还简介了相关甲壳素脱乙酰酶和溶菌酶等的概况。     

一种微生物酶法生产纤维低聚糖的新工艺

一种微生物酶法生产纤维低聚糖的工艺,是以经过预处理的纤维素为原料,真菌纤维素酶为初始酶制剂,采用纤维素“底物原位吸附-固液分离拆分-定向水解法”酶解制备纤维低聚糖,     

Enzymatic production and biological activities of chitosan oligosaccharides (COS): A review

Many researchers have focused chitosan as a source of potential bioactive material during past few decades. However, chitosan has several drawbacks to be utilized in biological applications, including poor solubility under physiological conditions. Therefore, a new interest has recently been emerged on partially hydrolyzed chitosan, chitosan oligosaccharides (COS). During the resent past, several technological approaches have been taken to prepare COS and, enzymatic preparation methods captured a great interest due to safe and non-toxic concerns. With time, new improvements were introduced to enzymatic production and presently it has been developed to a continuous production process. Many of the biological activities reported for COS, such as antimicrobial, anticancer, antioxidant, and immunostimulant effects are depend on their physico-chemical properties. In this review, we have summarized different enzymatic preparation methods of COS and some of their reported biological activities.     

Improvement of the yield of physiologically active oligosaccharides in continuous hydrolysis of chitosan using immobilized chitosanases

The continuous production of chitosan oligosaccharides using a packed-bed enzyme reactor was investigated as to the effects of the operation conditions on the yield of pentamers and hexamers of chitosan oligosaccharides. A column reactor packed with immobilized chitosanases prepared by the multipoint attachment method was used for continuous hydrolysis of chitosan. In this reactor, the decrease of the yield of the target intermediate oligosaccharides due to axial mixing was negligible. The surface enzyme density of the support and flow rate of the substrate solution significantly affected the maximum yield of pentamers and hexamers. These effects were summarized as a correlation with the Damk?hler number (Da), defined as the ratio of the maximum reaction rate to the maximum mass transfer rate. The optimum condition was determined based on Da. Under the optimized condition (Da = 0.12), pentamers and hexamers could be produced continuously for a month with a yield of over 35% (7 kg/m(3) in concentration).     

Effects of chitosan oligosaccharides on intestinal oxidative stress and inflammation response in heat stressed rats

This study was to verify the effects of chitosan oligosaccharides (COS) on intestinal integrity, oxidative status, and inflammatory response in a heat-stressed rat model. A total of 24 male Sprague Dawley rats were randomly divided into 3 treatment: CON, the control group; HS, the heat stress group; HSC, the heat stress group with 200 mg/kg COS. Rats in the HS and HSC group exposed to a cyclical heat stress for 7 consecutive days. The CON and HS group provided basal diet, and the HSC group provided the same diet with 200 mg/kg COS. Compared with the HS group, rats in the HSC group had lower serum diamine oxidase and D-lactate acid level, higher villus height of jejunum and ileum, lower malondialdehyde (MDA) content in duodenum, jejunum, and ileum mucosa, higher glutathione peroxidase (GSH-Px), catalase (CAT) and total antioxidant capacity (T-AOC) activity in duodenum mucosa, higher T-AOC activity in jejunum mucosa, and higher glutathione (GSH) level in ileum mucosa. Compared with the HS group, rats in the HSC group had higher interleukin-10 (IL-10) level, but lower tumor necrosis factor-α (TNF-α) level in duodenum, jejunum, and ileum mucosa. These results indicated that COS may alleviate intestinal damage under heat stress condition, probably by modulating intestinal inflammatory response and oxidative status.     

螺旋纤维床固定化生物反应器同时产酶降解壳聚糖的研究

采用多孔聚酯泡沫固定里氏木霉,在鼓泡柱固定化反应器中同时产酶降解壳聚糖。结果表明通过控制降解时间可以得到不同平均聚合度的降解产物。在28℃,pH4.8,通气量3vvm条件下,利用固定化反应器,在30d内连续进行10批同时产酶降解试验,结果发现壳聚糖酶活力和壳聚糖降解率能保持稳定。每批产生的壳聚糖酶活力平均达到0.15u/mL以上,壳聚糖平均降解率为73%。     

Production of fungal chitosan by solid substrate fermentation followed by enzymatic extraction

An improved method is described for the production of chitosan from mycelia of the fungus Gongronella butleri, grown by solid substrate fermentation on sweet potato. The chitosan was extracted subsequently by 11 M NaOH at 45 °C, and 0.35 M acetic acid at 95 °C. The resulting extract was clarified using a heat-stable, commercial -amylase. The yield (4–6 g/100 g mycelia) and relative number average molecular weight (44–54 kDa) of the chitosan increased with increasing duration of fungal growth up to the sixth day.     

Modelling and parameter estimation of the enzymatic synthesis of oligosaccharides by β‐galactosidase from Bacillus circulans

The aim of this research is to develop a model to describe oligosaccharide synthesis and simultaneously lactose hydrolysis. Model A (engineering approach) and model B (biochemical approach) were used to describe the data obtained in batch experiments with β‐galactosidase from Bacillus circulans at various initial lactose concentrations (from 0.19 to 0.59 mol·kg⁻¹). A procedure was developed to fit the model parameters and to select the most suitable model. The procedure can also be used for other kinetically controlled reactions. Each experiment was considered as an independent estimation of the model parameters, and consequently, model parameters were fitted to each experiment separately. Estimation of the parameters per experiment preserved the time dependence of the measurements and yielded independent sets of parameters. The next step was to study by ordinary regression methods whether parameters were constant under the altering conditions examined. Throughout all experiments, the parameters of model B did not show a trend upon the initial lactose concentration when inhibition was included. Therefore model B, a galactosyl‐enzyme complex‐based model, was chosen to describe the oligosaccharide synthesis, and one parameter set was determined for various initial lactose concentrations. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 64: 558–567, 1999.     

Structural changes of immunoglobulin G oligosaccharides with age in healthy human serum

Age-related changes of IgG N-linked oligosaccharides isolated from normal human serum are reported for 403 individuals (male 227 and female 176), varying in age from 0 to 85 years. The IgG N-linked oligosaccharides were released from the protein by digestion with a glycoamidase and reductively aminated with the fluorescent reagent, 2-aminopyridine. The mixture of pyridylaminated oligosaccharides was separated at high resolution by HPLC using a reverse-phase column. From the results of neutral oligosaccharide analysis, agalactosyl glycoform and bisecting GlcNAc-containing glycoform were shown to increase with increasing age. Spearman's correlation coefficients were 0.503 and 0.473, respectively. Thus, in healthy people, an increase of both types of glycoforms correlates weakly with age. In addition, differences were demonstrated between male and female groups in their twenties. The quantity of agalactosyl glycoform was found to be lower in females than in males. No significant differences, however, were observed in the quantity of bisecting GlcNAc-containing glycoforms between males and females. Abbreviations: Gal, D-galactose: GlcNAc, N-acetyl-D-glucosamine; Man, D-mannose; Fc, C-terminal half of the heavy chain dimers of IgG; HPLC, high-performance liquid chromatography; IgG, immunoglobulin G; ODS, octadecylsilyl; PA, pyridylamino This revised version was published online in November 2006 with corrections to the Cover Date.     

Characterization of oligosaccharides in milk of a mink, Mustela vison

Carbohydrates were extracted from a sample of milk from a mink, Mustela vison (Family Mustelidae). Free neutral and acidic oligosaccharides were isolated from the carbohydrate fraction and their chemical structures were compared with those of white-nosed coati (Nasua narica, Procyonidae) and harbour seal (Phoca vitulina, Phocidae) that we had studied previously. The ratio of free lactose to milk oligosaccharides was similar to that in milk of the white-nosed coati; in both species, this ratio was much lower than that in the milk of most eutherians. The neutral oligosaccharides of mink milk had alpha(1-3)-linked Gal or alpha(1-2)-linked Fuc residues at their non-reducing ends, as in the neutral oligosaccharides of white-nosed coati milk. Some of the neutral and acidic oligosaccharides, determined here, had been found also in harbour seal milk, but the harbour seal oligosaccharides did not contain alpha(1-3)-linked Gal residues.     

Efficient free fatty acid production in engineered Escherichia coli strains using soybean oligosaccharides as feedstock

To be competitive with current petrochemicals, microbial synthesis of free fatty acids can be made to rely on a variety of renewable resources rather than on food carbon sources, which increase its attraction for governments and companies. Industrial waste soybean meal is an inexpensive feedstock, which contains soluble sugars such as stachyose, raffinose, sucrose, glucose, galactose, and fructose. Free fatty acids were produced in this report by introducing an acyl‐ACP carrier protein thioesterase and (3R)‐hydroxyacyl‐ACP dehydratase into E. coli. Plasmid pRU600 bearing genes involved in raffinose and sucrose metabolism was also transformed into engineered E. coli strains, which allowed more efficient utilization of these two kinds of specific oligosaccharide present in the soybean meal extract. Strain ML103 (pRU600, pXZ18Z) produced ～1.60 and 2.66 g/L of free fatty acids on sucrose and raffinose, respectively. A higher level of 2.92 g/L fatty acids was obtained on sugar mixture. The fatty acid production using hydrolysate obtained from acid or enzyme based hydrolysis was evaluated. Engineered strains just produced ～0.21 g/L of free fatty acids with soybean meal acid hydrolysate. However, a fatty acid production of 2.61 g/L with a high yield of 0.19 g/g total sugar was observed on an enzymatic hydrolysate. The results suggest that complex mixtures of oligosaccharides derived from soybean meal can serve as viable feedstock to produce free fatty acids. Enzymatic hydrolysis acts as a much more efficient treatment than acid hydrolysis to facilitate the transformation of industrial waste from soybean processing to high value added chemicals. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 31:686–694, 2015     

High yield production of monomer-free chitosan oligosaccharides by pepsin catalyzed hydrolysis of a high deacetylation degree chitosan

The high molecular weight of chitosan, which results in a poor solubility at neutral pH values and high viscosity aqueous solutions, limits its potential uses in the fields of food, health and agriculture. However, most of these limitations are overcome by chitosan oligosaccharides obtained by enzymatic hydrolysis of the polymer. Several commercial enzymes with different original specificities were assayed for their ability to hydrolyze a 93% deacetylation degree chitosan and compared with a chitosanase. According to the patterns of viscosity decrease and reducing end formation, three enzymes--cellulase, pepsin and lipase A--were found to be particularly suitable for hydrolyzing chitosan at a level comparable to that achieved by chitosanase. Unlike the appreciable levels of both 2-amino-2-deoxy-D-glucose and 2-acetamido-2-deoxy-D-glucose monomers released from chitosan by the other enzymes after a 20h-hydrolysis (4.6-9.1% of the total product weight), no monomer could be detected following pepsin cleavage. As a result, pepsin produced a higher yield of chitosan oligosaccharides than the other enzymes: 52% versus as much as 46%, respectively. Low molecular weight chitosans accounted for the remaining 48% of hydrolysis products. The calculated average polymerization degree of the products released by pepsin was around 16 units after 20h of hydrolysis. This product pattern and yield are proposed to be related to the bond cleavage specificity of pepsin and the high deacetylation degree of chitosan used as substrate. The optimal reaction conditions for hydrolysis of chitosan by pepsin were 40 degrees C and pH 4.5, and an enzyme/substrate ratio of 1:100 (w/w) for reactions longer than 1h.