Another brick in the wall? Recent developments concerning the yeast cell envelope

To a yeast, the cell wall is an important living organelle performing a number of vital functions, including osmotic and physical protection, selective permeability barrier, immobilized enzyme support and cell-cell recognition and adhesion. Our basic model of wall structure involves attachment of secreted mannoproteins to a fibrillar inner layer of β-glucan. Recent work has emphasised the importance of chitin in lateral walls, examined the mechanisms of attachment of mannoproteins to the various cell wall glucan fractions and elucidated the pathway of β-glucan synthesis, by means of resistance to glucan-binding killer toxins. The conventional view of wall structure has been challenged by the discovery of a class of GPI-anchored, serine/threonine-rich wall-proteins. It has been suggested, that these proteins are anchored in the plasma membrane, spanning the wall with extended O-glycosylated structures and protruding out into the medium. Examination of these proteins shows a diversity of structures, sizes and behaviour that makes it improbable that these represent a new class of wall proteins. The possible roles of one of these proteins associated with flocculation, Flo1p, are discussed.     

燕麦β-葡聚糖溶液流体性能及其协同增稠效应研究

采用动态流变仪和乌氏粘度计测定动态粘度方法,系统研究燕麦β-葡聚糖流体力学性能和与 其它增稠剂协同增稠效应。     

MODIFIED FLUORIMETRIC FLOW-INJECTION-ANALYSIS (FIA) METHOD FOR THE DETERMINATION OF (1–3) (1–4)–B—D—GLUCAN

A simple system has been constructed for the quantitative determination of barley β-glucans. Measurements were made by the flow-injection-analysis (FIA) technique using the fluorescent dye Calcofluor as a specific reagent for (1·3) (1·4)–B—D—linkages. In this paper a single-line system is described involving only one pump samples of β-glucan being directly injected into the reagent stream. The reaction results in an increased intensity of fluorescence detected by a flow-through-cell fluorimeter and evaluated as peak heights or peak areas by a printer-plotter. The analysis is completed within 20s. The operational parameters were set during an optimization procedure.     

羧甲基-β-1,3-葡聚糖对人B淋巴母细胞的辐射防护作用

利用X射线辐照经羧甲基-β-1,3-葡聚糖预处理的人B淋巴母细胞(Human B lymphoblasts,HMy2.CIR),探究羧甲基-β-1,3-葡聚糖对辐射损伤的防护作用。采用CCK-8法检测细胞存活率,并筛选出最佳给药浓度和孵育时间(0.1μg/mL,72 h);流式细胞仪检测羧甲基-β-1,3-葡聚糖对辐照后HMy2.CIR细胞凋亡的影响;微核实验检测羧甲基-β-1,3-葡聚糖对辐照后HMy2.CIR细胞微核形成的影响;彗星实验检测对DNA损伤程度和修复的影响。结果表明,羧甲基-β-1,3-葡聚糖对HMy2.CIR无细胞毒性并具有增殖促进作用;羧甲基-β-1,3-葡聚糖能够抑制辐射造成的凋亡率和微核率的增加,降低DNA损伤程度,加快损伤DNA的修复。羧甲基-β-1,3-葡聚糖对HMy2.CIR细胞辐射损伤有防护作用,其机制可能与抑制辐射诱导的细胞凋亡和DNA损伤有关。     

Extraction of β–glucan by hydrothermal liquidization of barley grain in a semi-batch reactor

Subcritical water is a natural and green way for extraction of plant biomass components. Here, subcritical water was employed as a media to extract β–glucan from barley (Hordeum vulgare L.) at 130–170°C and 10 MPa. MALDI TOF–MS revealed that main massed peaks of water soluble products were distributed at 500-2900 m/z with a peak to peak mass difference of 162 m/z, consistent with the repeating unit of β–glucan. At 170°C, all amount of water soluble β–glucan has been extracted. Next, the liquid fraction products were atomized directly to produce microsphere particles.     

Barley β-glucan aerogels as a carrier for flax oil via supercritical CO2

Flax oil has important implications in human health, however, it must be protected in food systems to maintain bioactivity and avoid rancidity. Impregnation of active compounds in polymer networks using supercritical CO₂ (SCCO₂) has shown potential for their protection and delivery. Aerogels were formed with barley β-glucan using SCCO₂ drying. Impregnation of flax oil in barley β-glucan aerogels using SCCO₂ was evaluated when oil was added at different stages of the drying process (before, during and after drying) and under static and dynamic processes at different processing times (2, 6 and 8 h), temperatures (40 and 60 °C) and pressures (15 and 30 MPa). Impregnated aerogels were analyzed using Fourier-transform infrared spectrometry and scanning electron microscopy. Addition of oil during the drying process and the use of a dynamic flow regime resulted in the highest loading of aerogels. Oil loading increased with processing time, from 47.79% (lipid as % of total impregnated aerogel mass) after 4 h to 60.96% after 8 h, and with increasing pressure. Aerogel impregnation using SCCO₂ has potential as a delivery vehicle for high-value food grade compounds, including flax oil.     

以青稞β-葡聚糖为主要基质的保健果冻研制

以青稞β-葡聚糖为主要基质,研究一种降脂保健果冻的配方及制法。通过考察不同配方的组织形态、硬度和咀嚼感等9项感官指标初步筛选出果冻基质配方,以凝胶强度、黏度和持水性为指标用正交试验优化基质配方;以色泽、风味和口感为指标采用正交试验筛选添加有山楂和甘草提取物的青稞β-葡聚糖保健果冻的配方。结果表明:所得基质的配方(m/m)为5.0%青稞β-葡聚糖、0.5%明胶、5.0%甘油;保健果冻中添加剂用量(m/m)为山楂提取物1.5%、甘草提取物0.5%～2.5%、白砂糖8.0%。所制得的降脂保健果冻具有口感佳、安全防噎、入口即化的特点。     

青稞粉等原料及其制品中混联β-葡聚糖检测方法的研究

通过酶与样品中β-葡聚糖发生系列化学反应,采用分光光度法定性、定量检测β-葡聚糖。结果表明,采用酶法检测青稞粉等原料及其制品中混联β-葡聚糖,不仅稳定性好,回收率也很高,是一种较为理想的方法。     

The molecular weight,solubility and viscosity of oat beta-glucan affect human glycemic response by modifying starch digestibility

The interaction between oat β-glucan and other food components has the potential to influence starch digestibility and consequently affect its bioactivity in reducing glycemic responses. Blood glucose concentrations were measured before and after ingesting wheat and oat granolas, with 0.6 and 6.2 g of β-glucan, respectively, and two starch doses (40 and 60 g). As the in vitro extract viscosity of β-glucan increased, the in vitro starch digestibility was reduced and the glucose responses were lowered. The peak blood glucose response (PBGR) and the incremental area under the curve (iAUC) were lower in the 40 g than in the 60 g starch formulation. β-Glucan was significantly more active in reducing PBGR and iAUC when the β-glucan/starch ratio was 1.6:10 rather than 1.1:10. This information is valuable for new product development and for quality assessment of bioactive foods containing oat β-glucan.     

提取方法对产朊假丝酵母β-葡聚糖性质的影响

以产朊假丝酵母（Candida utilis）为原料,采用高压微射流均质法、超声波法及复合酶解生物法对酵母细 胞壁中的β-葡聚糖（yeast β-glucan,YG）进行提取（分别标为H-YG、U-YG和E-YG）。比较了3 种方法提取β-葡 聚糖的得率、纯度、分子质量分布、单糖组成等理化性质,并测定了3 种提取方法对样品抗氧化性和保湿性能的影 响。结果表明：3 种方法提取的β-葡聚糖纯度都在96%以上,高压微射流均质法得到的H-YG得率和含量最高,分 别为19.6%和97.5%;紫外光谱扫描显示多糖样品均不含核酸和蛋白质等杂质;单糖组成分析表明,3 种方法提取 的β-葡聚糖样品均是由葡萄糖组成的均一多糖;采用高效体积排阻色谱与多角度激光光散射联用仪测定了3 种方法 提取的β-葡聚糖的分子质量分布和多糖平均分子半径,表明3 种方法提取的β-葡聚糖的重均分子质量mw存在差异, 分别为1.611×106、4.763×106、2.661×105 g/mol,多分散系数分别为1.025、1.686、1.362,平均分子半径分别为 67.5、33.3、43.7 nm。抗氧化实验表明H-YG、U-YG和E-YG均具有一定的1,1-二苯基-2-三硝基苯肼自由基清除能 力,显示了其抗氧化能力。保湿实验表明：H-YG、U-YG和E-YG都有明显的体外保湿性能,H-YG体外保湿效果在 8～24 h内优于甘油;3 种方法提取的β-葡聚糖样品均对促进内源性天然保湿因子的生成效果显著,其中H-YG的促 进作用最为明显。研究结果表明,不同的提取方法影响酵母β-葡聚糖的理化性质,进而影响其生物活性,可根据其 不同特性应用于相应领域。