三种糖醇对高粱淀粉糊化特性和凝胶结构的影响

本文通过快速黏度分析仪(RVA)、物性测试仪(TPA)、差示扫描热量仪(DSC)、扫描电子显微镜(SEM),研究不同浓度的赤藓糖醇、木糖醇、麦芽糖醇(淀粉与糖醇比例为1:1、1:2、1:5,m/m),对高粱淀粉性质和高粱淀粉凝胶结构的影响。与原高粱淀粉相比,随着三种糖醇添加量的增加,相同温度下高粱淀粉的溶胀度下降,尤其是在75℃、85℃和95℃。RVA结果表明,随着糖醇添加量增加,高粱淀粉的峰值黏度和衰减值下降,然而其糊化温度增加。糖醇使高粱淀粉凝胶的硬度升高,而且随着糖醇添加量增加而增加。DSC结果表明,添加三种糖醇后,高粱淀粉的起始糊化温度,峰值糊化温度,终止糊化温度,焓变均增加,而且随着糖醇添加量增加而升高。从SEM可知,添加糖醇后的高粱淀粉凝胶的微观结构变得更紧密。     

响应面法优化产赤藓糖醇菌株RH-UV-L4-F9的发酵条件

为进一步提高糖蜜玉米浆发酵生产赤藓糖醇的产量,以高产赤藓糖醇耐高渗酵母RH-UV-L4-F9为出发菌株,采用响应面法优化发酵工艺参数。根据Box-Benhnken设计原理,在单因素试验基础上,采用三因素三水平响应面分析,确定最佳发酵工艺参数为：温度32.3℃、pH5.1、摇床转速176r/min。在此优化条件下赤藓糖醇产量达到166.89mg/mL,是初始条件下的1.2倍。     

碳源对圆酵母(Torula sp.)B84512发酵合成赤藓糖醇及副产物甘油的影响

研究了圆酵母(Torula sp.)B84512以不同碳源发酵产赤藓糖醇过程中副产物甘油的生成与消耗情况。发现该菌株在以任何碳源为底物发酵过程中均会产生甘油,且在发酵中后期甘油逐渐被消耗。以甘油为唯一碳源时该菌株合成赤藓糖醇的速率及产率均低于葡萄糖。葡萄糖为圆酵母B84512发酵产赤藓糖醇的最佳碳源。采用分批补料的方式提高赤藓糖醇的产率并期望能抑制甘油的生成,实验结果表明补料至总糖浓度为50%时赤藓糖醇产量最高为253 g/L,产率为1.03 g/(L.h)。但甘油产量与葡萄糖的浓度呈正相关,分批补料并不能有效抑制甘油的生成,反而导致发酵周期大大延长,对于工业化生产极其不利。通过对甘油的生成及消耗过程中关键酶胞浆3-磷酸甘油脱氢酶(ctGPD)、3-磷酸甘油酯酶(GPP)、线粒体3-磷酸甘油脱氢酶(mtGPD)酶活测定,确定胞浆3-磷酸甘油脱氢酶为甘油合成途径的关键酶,为以后对圆酵母B84512中甘油代谢途径的基因工程改造选育奠定了基础。     

原生质融合选育高产赤藓糖醇菌株的研究

在实验室经紫外诱变方法筛选到28株赤藓糖醇产生菌优良菌株基础上,采用原生质体电融合技术构建高产赤藓糖醇工程菌,对在实验过程中影响原生质体形成的各种因素以及影响电融合的各项参数进行初步研究,研究表明:酶解浓度为0.25%,酶解时间为20min,酶最适宜作用温度为35℃,最适pH值5～6。确定了最佳融合参数:交变电场强度为250V/cm,脉冲强度为6kV/cm,脉冲时间为30μs,脉冲个数为5个。融合菌株赤藓糖醇产量为120.6g/ml,葡萄糖转化率为53.2%。     

Identification of the gene PaEMT1 for biosynthesis of mannosylerythritol lipids in the basidiomycetous yeast Pseudozyma antarctica

The yeast Pseudozyma antarctica produces a large amount of glycolipid biosurfactants known as mannosylerythritol lipids (MELs), which show not only excellent surface‐active properties but also versatile biochemical actions. To investigate the biosynthesis of MELs in the yeast, we recently reported expressed sequence tag (EST) analysis and estimated genes expressing under MEL production conditions. Among the genes, a contiguous sequence of 938 bp, PA_004, showed high sequence identity to the gene emt1, encoding an erythritol/mannose transferase of Ustilago maydis, which is essential for MEL biosynthesis. The predicted translation product of the extended PA_004 containing the two introns and a stop codon was aligned with Emt1 of U. maydis. The predicted amino acid sequence shared high identity (72%) with Emt1 of U. maydis, although the amino‐terminal was incomplete. To identify the gene as PaEMT1 encoding an erythritol/mannose transferase of P. antarctica, the gene‐disrupted strain was developed by the method for targeted gene disruption, using hygromycin B resistance as the selection marker. The obtained ΔPaEMT1 strain failed to produce MELs, while its growth was the same as that of the parental strain. The additional mannosylerythritol into culture allowed ΔPaEMT1 strain to form MELs regardless of the carbon source supplied, indicating a defect of the erythritol/mannose transferase activity. Furthermore, we found that MEL formation is associated with the morphology and low‐temperature tolerance of the yeast. Copyright © 2010 John Wiley & Sons, Ltd.     

营养型芦笋醋饮料的研制

介绍了以芦笋为原料发酵成醋,然后配制成芦笋醋酸饮料的工艺过程。该产品不仅营养价值高,风味独特,而且还具有一定的保健作用。     

Torulopsis sp.ERY237产赤藓糖醇工艺条件的研究

以Torulopsis sp.ERY237作为出发菌株,考察了不同碳源、氮源、无机盐类以及温度等因素对菌种产赤藓糖醇的影响,建立和优化了赤藓糖醇摇瓶发酵培养基配方、发酵工艺条件,同时研究了发酵过程中菌体生物量、pH值、产物浓度的动态变化。结果表明,菌株的最适培养基配方为(g/L):葡萄糖300,玉米浆3.5,C_([Cu~(2+)])1.5,C_([Mn~(2+)])10;适宜的培养条件为初始pH值自然,温度30℃,装液量50 mL/500 mL,转速200 r/min,在此条件下培养132 h赤藓糖醇产量达87.8 g/L,是优化前产量的1.9倍,发酵时间缩短了12 h。     

Thermal conductivity measurement of erythritol,xylitol, and their blends for phase change material design: A methodological study

This work presents and discusses a detailed thermal conductivity assessment of erythritol, xylitol, and their blends: 25 mol% erythritol and 80 mol% erythritol using the transient plane source (TPS) method with a Hot Disk Thermal Constants Analyzer TPS‐2500S. Thereby, the thermal conductivities of xylitol, 25 mol% erythritol, 80 mol% erythritol, and erythritol were here found for respectively in the solid state to be 0.373, 0.394, 0.535, and 0.589 W m^?1 K^?1 and in the liquid state to be 0.433, 0.402, 0.363, and 0.321 W m^?1 K^?1. These obtained results are comprehensively and critically analyzed as compared to available literature data on the same materials, in the phase change materials (PCMs) design context. This study clearly indicates that these thermal conductivity data in literature have considerable discrepancies between the literature sources and as compared to the data obtained in the present investigation. Primary reasons for these disparities are identified here as the lack of sufficiently transparent and repeatable data and procedure reporting, and relevant standards in this context. To exemplify the significance of such transparent and repeatable data reporting in thermal conductivity evaluations in the PCM design context, here focused on the TPS method, a comprehensive measurement validation is discussed along various residual plots obtained for varying input parameters (ie, the heating power and time). Clearly, the variations in the input parameters give rise to various thermal conductivity results, where choosing the most coherent result requires a sequence of efforts per material, because there are no universally valid conditions. Transparent and repeatable data and procedure reporting are the key to achieve comparable thermal conductivity results, which are essential for the correct design of thermal energy storage systems using PCMs.     

N2O5/HNO3硝化合成1,2,3,4-丁四醇四硝酸酯

以赤藓糖醇为原料,利用绿色硝化剂五氧化二氮（N₂O₅）在硝酸(HNO₃)介质中硝解制得1,2,3,4-丁四醇四硝酸酯（ETN）。与现有混酸法相比,该反应可在无硫酸(H₂SO₄)环境下进行,后处理简单,废酸污染小。试验探讨了投料比、反应温度和反应时间对ETN产率的影响,用扫描电镜SEM、红外光谱IR等对不同ETN晶体的形态进行了表征。结果表明,投料比m(赤藓糖醇):m(N₂O₅):V(HNO₃)=2.5 g :4.0 g :20.0 mL、反应温度为20 ℃、反应时间为2 h时,ETN的产率最高,达76.6%。同时,3种不同晶体形态的ETN具有相同的特征峰。