大蒜果聚糖∶果聚糖1-果糖基转移酶的酶学特性

大蒜中主要干物质为多糖,其中主要糖类为果聚糖,具有多种保健作用。本文研究了大蒜中果聚糖∶果聚糖1-果糖基转移酶（Fructan∶fructan 1-fructosyltransferase,1-FFT）的酶学特性,为阐明大蒜在采后贮藏、保鲜及深加工过程中果聚糖含量的变化提供依据。结果表明:当以1-蔗果三糖为底物时,1-FFT仅催化生成蔗果四糖,且无其它结构的四糖生成;大蒜1-FFT主要存在于40%⁵0%硫酸铵部分;其最适p H为6.0,在p H 5.5⁶.5条件下1 h内保持稳定;最适温度为25℃,在15²5℃条件下1 h内可保持稳定;低浓度Mn²⁺、Mg²⁺、Fe³⁺促进1-FFT活力,Cu²⁺、Zn²⁺、Ag⁺抑制1-FFT活力;1-FFT活力随底物浓度升高而增大,其米氏常数Km=0.6977 mol/L,最大反应速率Vmax=116.23μg/h。大蒜1-FFT活力受p H、温度、不同金属离子及底物浓度影响,调节以上因素有助于调控大蒜果聚糖代谢、保持大蒜品质及延长大蒜贮藏期。      

大蒜果聚糖外切酶的一些酶学特征研究

目的：研究大蒜(Allium sativum L.)果聚糖水解酶(FEH)的酶学特征。方法：采用硫酸铵分级沉淀确定FEH 所在的沉淀组分,采用薄板层析和离子色谱法研究酶解产物,通过3,5- 二硝基水杨酸(DNS)法测定还原糖的变化量计算酶活力,进而研究FEH 的酶切位点,研究温度、pH 值、离子强度、底物质量浓度对FEH 活力的影响。结果：大蒜FEH 存在于0～20% 硫酸铵饱和度组分,根据酶解产物判断该酶属于外切酶,最适反应温度为45℃,最适反应pH 值为5.5,最适离子强度1.5mol/L 氯化钠,最适反应质量浓度为4mg/mL。结论：存在于大蒜中的果聚糖外切酶会影响大蒜加工产品的质量和保鲜大蒜贮藏的糖代谢。     

Acute bovine laminitis: a new induction model using alimentary oligofructose overload

Twelve dairy heifers were used to examine the clinical response of an alimentary oligofructose overload. Six animals were divided into 3 subgroups, and each was given a bolus dose of 13, 17, or 21 g/kg of oligofructose orally. The control group (n = 6) was sham-treated with tap water. Signs of lameness, cardiovascular function, and gastrointestinal function were monitored every 6 h during development of rumen acidosis. The heifers were euthanized 48 and 72 h after administration of oligofructose. All animals given oligofructose developed depression, anorexia, and diarrhea 9 to 39 h after receiving oligofructose. By 33 to 45 h after treatment, the feces returned to normal consistency and the heifers began eating again. Animals given oligofructose developed transient fever, severe metabolic acidosis, and moderate dehydration, which were alleviated by supportive therapy. Four of 6 animals given oligofructose displayed clinical signs of laminitis starting 39 to 45 h after receiving oligofructose and lasting until euthanasia. The lameness was obvious, but could easily be overlooked by the untrained eye, because the heifers continued to stand and walk, and did not interrupt their eating behavior. No positive pain reactions or lameness were seen in control animals. Based on these results, we conclude that an alimentary oligofructose overload is able to induce signs of acute laminitis in cattle. This model offers a new method, which can be used in further investigation of the pathogenesis and pathophysiology of bovine laminitis.     

Reduced test-day milk fat percentage in cows diagnosed with claw horn lesions during routine claw trimming

The objective of this study was to investigate whether cows diagnosed with claw horn lesions during routine claw trimming had an altered milk fat percentage on test days preceding the diagnosis, compared with cows without such lesions. Data included date of trimming, cow number, type, and location of claw lesions recorded by a professional claw trimmer during routine trimming sessions on 11 commercial dairy farms, and monthly test-day data. Recordings from 4,381 cows were included in the analysis. Three hundred seventy-two (8.5%) cows were diagnosed with at least one claw lesion. One hundred ninety-five (4.4%) cows were classified as cases of laminitis and 169 cows (3.9%) were classified as cases of infectious claw diseases. Average test-day milk fat percentage was estimated from monthly test-day data using a mixed model with a random farm effect and a marginal effect for repeated measurements. Estimated milk fat percentage of cows classified as cases of laminitis on the day of claw trimming was 0.17 and 0.22% less than that of cows with either no claw lesion or those with an infectious claw disease, on test days occurring 2 and 5 mo before claw trimming, respectively. To the best of our knowledge, decreased test-day milk fat percentage in dairy cows diagnosed with claw horn lesions has not been described. Because decreased milk fat and claw horn lesions have both been associated with subacute ruminal acidosis, it is plausible that subacute ruminal acidosis played a role in the association we found. A prospective study with a greater frequency of claw examinations would be necessary to help clarify these associations. Our findings indicate that test-day milk fat might be useful as a tool for monitoring cows and farms at risk for claw horn lesions.     

Influence of transition diets on occurrence of subclinical laminitis in Holstein dairy cows

Pre- and postpartum diets varying in energy and fiber were studied for effects on subclinical laminitis in Holstein cows. Also, ruminal acidosis was examined relative to sole hemorrhages and ulcers. Cows (n = 98) were assigned to a 2 x 2 factorial arrangement of treatments in a randomized complete block. Diets high in net energy of lactation (NE(L)) and low fiber were classified as high NE(L), whereas low NE(L) and higher fiber were defined as low NE(L). Two diets were fed for 3 wk before calving and 2 others fed for 3 wk postpartum resulting in 4 treatment combinations: high NE(L), low NE(L); high NE(L), high NE(L); low NE(L), low NE(L); and low NE(L), high NE(L). Levels of NE(L) (Mcal/kg DM), percentage of acid detergent fiber, and percentage of neutral detergent fiber for low NE(L) vs. high NE(L) prepartum diets, were 1.51, 30.2, 47.2 vs. 1.65, 23.4, 39.8, respectively, and 1.70, 22.4, 36.8 vs. 1.77, 17.5, 31.4 for low NE(L) vs. high NE(L) lactating diets, respectively. A single diet was fed after 21 d in milk (DIM). Measures of hoof discoloration, hemorrhage, and/or ulcer formation were done at about 45 d before calving, and near 28 and 70 DIM. Rumenocentesis was performed 14 d before calving and at 8, 22, and 70 DIM. Hoof scores among treatments were similar at 28 DIM. The low NE(L), high NE(L) group had less desirable hoof scores than high NE(L), high NE(L), or low NE(L), low NE(L) groups from 55 to 75 DIM. Rumen pH did not differ by treatment before calving. The lowest postpartum rumen pH was significantly lower and rates of ruminal acidosis (pH < or = 5.8) at 8 and 22 DIM were higher for groups fed high NE(L) after calving. No direct relationship between low postpartum rumen pH and hoof scores on individual cows was found. Low NE(L) before calving and high NE(L) right after calving may increase risk of subclinical laminitis if not carefully managed.     

菊粉型果聚糖在无麸质产品中应用的研究进展

由于谷蛋白相关疾病与含谷蛋白食物的摄入有关,无麸质产品在食品工业中受到广泛关注,菊粉型果聚糖已成为无麸质产品的有益成分.本文介绍了菊粉型果聚糖在无麸质产品中应用的技术背景,阐述了菊粉型果聚糖的物理化学特性及其作为组成部分对无麸质产品的技术性能和感官质量的影响,分析了菊粉型果聚糖添加到无麸质产品后与其他成分和添加剂之间的...     

Invited review: formation of keratins in the bovine claw: roles of hormones, minerals, and vitamins in functional claw integrity

Keratins are the characteristic structural proteins of the highly cornified epidermis of the skin, feathers, and hoof. Keratin proteins provide the structural basis for the unique properties of the biomaterial horn and its protective function against a wide range of environmental factors. Hoof horn is produced through a complex process of differentiation (keratinization) of epidermal cells. Formation and biochemical binding of keratin proteins and synthesis and exocytosis of intercellular cementing substance (ICS) are the hallmarks of keratinization. It is finalized by the programmed death of the living epidermal cells, i.e., cornification, that turns the living epidermal cells into dead horn cells. The latter become connected by the intercellular cementing substance. The functional integrity of hoof horn essentially depends on a proper differentiation, i.e., keratinization of hoof epidermal cells. Keratinization of hoof epidermis is controlled and modulated by a variety of bioactive molecules and hormones. This process is dependent on an appropriate supply of nutrients, including vitamins, minerals, and trace elements. Regulation and control of differentiation and nutrient flow to the epidermal cells play a central role in determining the quality and, consequently, the functional integrity of hoof horn. Decreasing nutrient supply to keratinizing epidermal cells leads to horn production of inferior quality and increased susceptibility to chemical, physical, or microbial damage from the environment. A growing body of evidence suggests that hormones, vitamins, minerals, and trace elements play critical roles in the normal development of claw horn and correct keratin formation.     

菊芋中菊糖提取及果糖制备研究进展

菊芋的块茎富含菊糖,由菊糖可以制备果聚糖,低聚果糖在改善肠道功能方面具有积极作用,高聚果糖能制备超高果糖浆。根据近年来国内外的研究报道,综述了水热法、超声波辅助法、微波辅助法、酶法提取菊糖的原理、工艺流程和最新进展,以及菊糖通过酸法和酶解法制备果糖的工艺、果糖的生理功能,提出了存在的问题并对发展前景进行了展望。      

Biomechanics and histology of bovine claw suspensory tissue in early acute laminitis

Weakening of the suspensory tissue supporting the pedal bone is the central issue in the theory of acute bovine laminitis, but this aspect has never been tested. The objective of this study was to investigate the effect of laminitis on the suspensory tissue. The hypothesis was that clinical and histological signs of acute laminitis are associated with decreased strength of the suspensory tissue of the bovine claw. Nonpregnant dairy heifers (n = 10) received oral oligofructose overload (17 g/kg of body weight) and were killed 24 (n = 4) and 72 h (n = 6) after overload. Control heifers (n = 6) received tap water and were killed at 72 or 96 h. Clinical, orthopedic, and histological examinations were carried out to confirm the occurrence of laminitis. After euthanasia, 2 adjacent tissue samples including the horn wall, lamellar layer, dermis, and pedal bone were cut from the dorso-abaxial aspect of each claw. Tissue samples were kept on ice until mounted on a mechanical testing frame, fixed by horn and bone, and loaded to failure. A stress displacement curve was generated and measurements of physiological support (force needed to displace 1 mm beyond first resistance) and maximal support (force needed to break the tissue) were recorded. Heifers treated with oligofructose developed clinical signs consistent with ruminal and systemic acidosis after treatment as well as acute laminitis, characterized by weight shifting (35% of observations vs. 6% in controls), moderate lameness (100 vs. 17%, score of 3 out of 5 at 72 h), and reaction to hoof testing (30 and 50% at 48 and 72 h, respectively, vs. 0% in controls). Histological examination of claws from heifers killed 72 h after overload showed changes consistent with acute laminitis, including stretched lamellae, wider basal cells with low chromatin density, and a thick, wavy, and blurry appearance of the basement membrane. Biomechanical results showed no effect of oligofructose overload on physiological support of the suspensory tissue at 24 and 72 h after overload; in contrast, overload increased maximal support of the tissue 72 h after overload. Herd of origin and location of the sample had large effects on both physiological support and maximal support (herd = 547 N/cm²; location = 531 N/cm²) of claw suspensory tissue (herd = 260 N/cm²; location = 327 N/cm²). Despite clinical and histological signs of laminitis, no weakening of the suspensory tissue of the bovine claw was detected at 24 and 72 h after oligofructose overload. Herd factors appeared to be important for claw suspensory tissue strength.     

Changes in terpene content in milk from pasture-fed cows

Changes of terpene content in milk from cows grazing natural diversified upland pasture were examined in this observational trial. A homogeneous plot divided into 2 subplots was used from May 31 to July 1, 2003 (first growth) and again from October 1 to October 7, 2003 (vegetative regrowth). Each subplot was grazed by 6 dairy cows in 2 ways: strip grazing (SG), with new allocations of pasture strips at 2-d intervals, and paddock grazing (PG). The PG subplot was divided into 3 paddocks and the cows were moved to a new paddock on June 13 and June 24, 2003. Milk from the 6 cows was collected twice a week, pooled, and used for terpene analyses by dynamic headspace gas chromatography-mass spectrometry system. Twenty mono- and 23 sesquiterpenes desorbing from the milk fat were separated. The most abundant monoterpenes were β-pinene, α-pinene, γ-terpinene, limonene, α-tujene, terpinolene, and α-phellandrene. The most abundant sesquiterpenes were β-caryophyllene, α-copaene, β-cedrene, transmuurola-4-(14)-5-diene, β-bisabolene, and δ-cadinene. Both mono- and sesquiterpenes in SG milk increased across time with an 8-fold increase in total terpenes in milk from the beginning to the end of June. In parallel, dicotyledons, including the main terpene-rich plants, increased from 17 to 31% of total biomass of the vegetation and the development of Dactylis glomerata progressed from boot to ripening stage. The terpenes in PG milk were equivalent to those in SG milk for the first paddock at the beginning of June and remained constant or doubled for the sum of mono- and sesquiterpenes, respectively. The lower variability of the PG milk terpene content could be related to the opportunity that PG cows had to choose ingested herbage, whereas the SG cows had limited choice within the smaller allocated pasture strips. Milk from cows grazing regrowth pastures in October contained low levels of terpenes, and values were similar for PG and SG milks. Change in the sum of monoterpenes is representative of changes for most monoterpenes (except for limonene) and, conversely, the change in the sum of sesquiterpenes mainly reflected changes in β-caryophyllene and α-copaene. In addition to effects of botanical composition of pasture, it appears that terpene content in milk may vary according to factors linked to grazing management that need more intensive study. Nevertheless, current results raise questions about the precision of terpenes as feed tracers.     

Oligofructose overload induces lameness in cattle

The aim was to describe the clinical orthopedic implications of oligofructose overload. A group of 8 nonpregnant dairy heifers were given an oral dose of oligofructose (17 g/kg of body weight). At predefined times during a period spanning 3 d before and 9 d after oligofructose overload, the heifers underwent a clinical examination including locomotion scoring, hoof-testing, and palpation of tarso-crural joints, as well as the collection of blood and ruminal fluid samples. Locomotion sessions were videotaped; subsequently, locomotion was blind-scored. Locomotion scores increased after oligofructose overload and declined toward the end of the study period. The greatest locomotion scores were recorded on d 3 to 5 (60 to 120 h) where 12 of 42 (29%) locomotion scores were 3 and 13 of 42 (32%) were score 2. Positive reactions to hoof-testing were observed from 30 h after oligofructose overload and reached a maximum on d 7 and 9 where 12 of 28 (43%) reactions were marked positive. Distension of the tarso-crural joints was observed from 24 h after oligofructose overload, with maximum distension being observed on d 2, in which 44 of 56 (79%) of observed joints were either moderately or severely distended. The heifers developed classic signs of acute ruminal and systemic acidosis after the oligofructose overload (ruminal pH 4.3 ± 0.07, standard base excess −10.8 ± 2.3 at 18 h). With few exceptions, clinical and laboratory variables returned to normal within 9 d of oligofructose overload. But, good body condition and previous feeding with grass apparently predisposed the heifers to more severe systemic affection. Oligofructose overload in dairy heifers induced ruminal and systemic acidosis, diarrhea, dehydration, and, subsequently, lameness, claw pain, and joint effusion, collectively interpreted as signs of acute laminitis. Oligofructose overload at 17 g/kg of body weight represented a relatively mild laminitis model in cattle, as demonstrated by a reasonably quick recovery from systemic as well as orthopedic signs.     

A Simple Method for Estimation of Neutral Detergent-Soluble Fibre

A method was developed to estimate the neutral detergent-soluble fibre (NDSF) content of feeds. Citrus pulp, sugar beet pulp, soybean hulls, separated leaves and stems from mature and immature alfalfa, red clover, reed canarygrass and timothy were analysed. Half-gram samples were stirred at room temperature for 4 h with 100 ml of 90:10 (v/v) ethanol/water to extract low molecular weight substances, crude protein (CP) and ash to produce ethanol-insoluble residues (EIR). Samples were refluxed for 1 h with neutral detergent solution and heat stable α-amylase to extract low molecular weight substances, NDSF, starch, CP and ash to produce neutral detergent residues (NDF). The EIR and NDF were analysed for organic matter (OM; EIROM; NDFOM) and CP (EIRCP; NDFCP), and EIR was analysed for starch. Values were expressed as proportions of the original sample dry matter. The NDSF was calculated as the difference in OM mass between EIR and NDF after correction for CP and starch by the equation: EIROM-NDFOM-EIRCP+NDFCP-EIR starch. Extractions with 90:10 (v/v) ethanol/water gave a higher yield of EIR and NDSF than did 80: 20 (v/v) ethanol/water. The method gave good precision and is convenient for assessing NDSF content of feeds. © 1997 SCI.     

Grazing season length and stocking rate affect milk production and supplementary feed requirements of spring-calving dairy cows on marginal soils

The objective of this study was to investigate the effect of increasing stocking rate (SR) and extending grazing season (GS) length on pasture and animal productivity on a marginal, poorly draining soil type. The study was a multiyear (2017 to 2020, inclusive) whole farm systems evaluation with a 2 × 2 factorial experimental arrangement of treatments. The systems evaluated comprised 2 GS lengths, average (AGS; 205 d) and extended (EGS; 270 d), and the 2 whole farm stocking rates were medium (2.5 cows/ha) and high (2.9 cows/ha). We used this study design to create 4 grazing system intensities (500, 600, 700, and 800 cow grazing days per hectare per year). In 2017, cows were randomly allocated to 1 of the 4 whole farm systems precalving and remained on the same treatments for the duration of the study. We found no significant differences in total average annual pasture production [14,133 ± 538 kg of dry matter (DM) per hectare] or sward chemical composition between GS and SR treatments over the 4-yr period, with the exception of average crude protein content, which was lower for EGS (211 g/kg DM) compared with AGS (218 g/kg DM). Grazed pasture production was significantly increased in EGS treatments (+758 kg of DM/ha) compared with AGS (9,917 kg of DM/ha), whereas conserved silage DM production was greater for AGS (+716 kg of DM/ha) compared with EGS (3,583 kg of DM/ha). Neither GS nor SR had a significant effect on daily or cumulative lactation milk and fat plus protein production per cow (5,039 and ±440 kg, respectively). Increasing SR resulted in increased milk fat plus protein yield per hectare based on increased grazed pasture utilization. These results add further credence to the important additive contributions of both extended grazing and SR intensification to achieve high levels of grazed pasture utilization and milk production per hectare while reducing supplementary feed requirements within spring-calving grazing systems.     

Short communication: infrared thermography and visual examination of hooves of dairy cows in two stages of lactation

Hooves of 16 lactating Holstein cows were examined twice for sole hemorrhages and underrun heels. Images of hooves were taken using infrared thermography to determine the temperatures of the coronary band and that of a control area above the coronary band. To adjust for skin (control) temperature, the difference (ΔT) between the coronary band and the control area was calculated. Effects of stage of lactation, that is, ≤200 d in milk (DIM) vs. >200 DIM, on temperature of the coronary band, ΔT, and visual abnormalities were determined. Temperatures of the coronary bands of cows were greater for cows ≤200 DIM (n = 17) than for cows (n = 15) in late lactation (25.5 ± 1.3 vs. 21.0°C). The ΔT was also greater for cows ≤200 DIM compared with those >200 DIM (6.1 ± 0.8 vs. 3.3 ± 0.9°C). The ΔT was greater for lateral claws than for medial claws (5.2 ± 0.6 vs. 4.2 ± 0.6°C). Chi-square analysis revealed that the frequency of sole hemorrhages in hind lateral claws was significantly higher for cows ≤200 DIM compared with those in late lactation. In contrast, underrun heel was more frequently observed among cows >200 DIM. Increased temperatures of the coronary band and ΔT in early/midlactation coincided with increased incidence of sole hemorrhages, but not to incidences of underrun heels. Because higher hoof temperatures occurred in cows ≤200 DIM compared with cows later in lactation, measurement of hoof temperatures among cows in early lactation may be useful in monitoring hoof health.     

Restricting daily time at pasture at low and high pasture allowance: Effects on pasture intake and behavioral adaptation of lactating dairy cows

In pasture-based dairy systems, daily time at pasture is restricted during several periods of the year. The aim of this experiment was to evaluate the effect of restricting time at pasture on milk yield, pasture dry matter (DM) intake, and grazing behavior of dairy cows according to pasture allowance (PA), which partly defines pasture availability. The experiment was carried out in spring on strip-grazed perennial ryegrass pastures. The 6 treatments consisted of 3 durations of daily time at pasture [U: unrestricted day and night grazing (22 h at pasture); R9: 1 grazing session restricted to 9 h between the 2 milkings; R5: 2 grazing sessions of 2.75 h after each milking) compared at low and high PA (13 and 24 kg of DM/d per cow >5 cm, respectively). Eighteen mid-lactation Holstein dairy cows were used according to a 6 × 4 incomplete Latin square design replicated 3 times with four 14-d periods. Pasture DM intake was measured by the ytterbium-fecal index method and grazing behavior from portable devices. On average, restricting time at pasture from U to R (mean of R5 + R9) decreased pasture intake by 2.9 kg of DM, milk yield by 1.3 kg, and milk protein concentration by 0.11%, and increased milk fat concentration by 0.20%. Pasture intake and milk yield did not differ significantly between R9 and R5. The reduction of pasture intake and milk yield with decreasing time at pasture was greater at high compared with low PA. Grazing times were 536, 414, and 305 min, representing proportions of time spent grazing of 0.40, 0.77, and 0.93 for treatments U, R9, and R5, respectively. The reduction of grazing time with decreasing time at pasture was greater at high compared with low PA. Pasture intake rate greatly increased with decreasing time at pasture, but mainly on R5 (29.8, 31.6, and 42.1 g of DM/min for U, R9, and R5, respectively). The effect of time at pasture on pasture intake rate was unaffected by PA. In conclusion, the effect of restriction of time at pasture on pasture intake and milk yield becomes more marked as PA increases. Cows offered only 2 grazing sessions of 2.75 h after each milking maximized pasture intake rate and consumed pasture as much as in one 9-h grazing session.     

Effects of low rumen-degradable protein or abomasal fructan infusion on diet digestibility and urinary nitrogen excretion in lactating dairy cows

Post-ileal carbohydrate fermentation in dairy cows converts blood urea nitrogen (BUN) into fecal microbial protein. This should reduce urinary N, increase fecal N, and reduce manure NH₃ volatilization. However, if intestinal BUN recycling competes with ruminal BUN recycling, hindgut fermentation may reduce NH₃ for rumen microbial protein synthesis. Eight lactating Holstein cows were used in a replicated 4 × 4 Latin square design with 14-d periods. Treatments were arranged as a 2 × 2 factorial. Diets contained either adequate rumen-degradable protein (RDP; high RDP) or were 28% below predicted RDP requirements (low RDP). Cows received abomasal infusions of either 10 L/d of saline or 10 L/d of saline containing 1 kg/d of inulin. We hypothesized that reducing ruminal NH₃, either by restricting RDP intake or by diverting BUN to feces with inulin, would reduce rumen microbial protein synthesis, as would be evidenced by significant main effects of treatments on rumen NH₃, milk production, and urinary purine derivative excretion. Furthermore, we thought it likely that effects of inulin might be greater when rumen NH₃ was already low, as would be indicated by significant interactions between inulin infusion and dietary RDP level on rumen NH₃, milk production, and urinary purine derivative excretion. Rumen NH₃ was reduced by the low-RDP diet, but urinary purine derivative excretion and milk production were unaffected. However, the low-RDP diet reduced apparent total tract digestibility of OM and starch and reduced in situ rumen NDF digestibility. Abomasal inulin reduced the BUN concentration but did not affect milk yield or rumen NH₃, suggesting that RDP requirements are not affected by hindgut fermentation. Inulin shifted 23 g/d of N from urine to feces. However, based on fecal purine excretion, we estimated that only 8 g/d of the increased fecal N was due to increased fecal microbial output. Inulin reduced true digestibility of dietary protein or increased nonmicrobial as well as microbial endogenous losses. This latter effect may be an artifact of our experimental model that delivers easily fermented, soluble fiber to the small intestine. Normal dietary alterations to similarly increase large intestinal fermentation would probably arise from larger quantities of less rapidly digested carbohydrates. Increasing hindgut fermentation in practical diets should reduce manure NH₃ volatilization without impairing rumen fermentation, but the reduction is likely to be small.     

732离子交换树脂和DEAE-23树脂纯化大蒜多糖比较

大蒜多糖是具有多种生物活性的杂果聚糖,为探讨其工业化制备的方法,对比了强酸性阳离子交换树脂（732）和DEAE-23树脂制备该多糖的流速、交换容量等操作参数,分析了其产品的蛋白质含量、大蒜多糖产量、红外光谱等质量指标.结果表明：732离子交换树脂和DEAE-23树脂制备的大蒜多糖红外光谱基本一致,产率分别为12.3%和10.37%,732DEAE-23树脂离子交换树脂的交换容量较大,制备过程简单、速度较快,成本较低,是较适宜工业化生产大蒜多糖的方法.     

植物中特定果聚糖的合成研究进展

果聚糖,是由多种细菌和植物产生的一种果糖聚合物,是重要的储藏碳水化合物。菊苣是一个商业果糖生产作物。研究表明,果聚糖在菊苣体内的生物合成是难以控制的。特制果聚糖-具有所需的聚合物长度和连接类型的果聚糖,是原本非果聚糖积累植物引进果糖基转移酶基因的成功表达。文章较为系统地综述了果聚糖的生物合成及修改,特定果聚糖的合成,果聚糖的功能及应用前景等方面的研究进展。