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本文以α-纤维素为原料,ClSO_3H-DMF为酯化剂,采用多相硫酸酯化法制备纤维素硫酸酯(Cellulose Sulfate,CS)。通过元素分析确定了CS的硫酸酯基取代度为2.0左右,13C-NMR测试表明,CS的硫酸酯基取代模式是C-6完全硫酸酯基取代和C-2部分或完全取代。CS在去离子水中具有良好的溶解性。根据相近取代度的CS系列产物的分子量与特性粘度的关系,通过Mark-Houwink拟合,确定了CS的糖链在稀溶液中呈现一种较为紧密的构象。在浓溶液中,CS的动力粘度随浓度增加而增大;外加盐能够促进CS聚电解质的电荷排斥作用,导致其动力粘度增加;添加二价盐Ca~(2+)可产生CS糖链的络合,显著提高CS的动力粘度;溶液pH环境为影响CS动力粘度的主要因素之一,在中性条件下动力粘度最大,酸性或碱性环境都会使其动力粘度下降。 相似文献
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探讨硫酸酯化修饰对鱼腥草多糖清除自由基活性的影响,采用浓硫酸法对鱼腥草多糖进行硫酸酯化修饰,对不同取代度硫酸酯化鱼腥草多糖的羟自由基(·OH)和二苯基苦酰肼基自由基(DPPH·)体外清除活性进行比较,考察清除活性与取代度之间的关系。结果表明,在酯化时间分别为30, 60, 90, 120和150 min下得到的5个不同取代度改性产物(S-HCP 1、S-HCP 2、S-HCP 3、S-HCP 4和S-HCP 5),对DPPH·的清除活性随着浓度和取代度增加均增强,对·OH的清除活性在取代度大于0.6时,随浓度和取代度增加而增强,表明硫酸化多糖清除自由基活性与其硫酸化的取代度相关。 相似文献
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《食品与发酵工业》2020,(4)
该文对海参岩藻聚糖硫酸酯进行硫酸酯化修饰,并比较其酯化修饰前后的结构特征及抗氧化活性。分别采用三氧化硫-DMF法和三氧化硫-吡啶法制备硫酸酯化海参岩藻聚糖硫酸酯,以取代度为考察指标,研究了反应温度、酯化剂用量、反应时间对酯化效果的影响。结果表明,三氧化硫-DMF法的最佳修饰条件为:反应温度为40℃、酯化剂用量1. 2 g、反应时间为3 h,产品取代度可达15. 63;三氧化硫-吡啶法的最佳修饰条件为:反应温度为90℃、酯化剂用量1. 2 g、反应时间为3 h,产品取代度可达13. 31。抗氧化活性测定结果显示,硫酸酯化海参岩藻聚糖硫酸酯对DPPH·和·OH的清除率均显著提高,且三氧化硫-DMF法所得产品的抗氧化活性略高。 相似文献
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采用氯磺酸-吡啶法合成硫酸酯化葛仙米多糖,利用正交设计对酯化试剂比例、反应温度及反应时间进行优化。通过傅里叶红外光谱分析酯化前后的结构差异,氯化钡-明胶比浊法测定取代度,并分析红外光谱法与取代度之间的相关性。结果表明:葛仙米多糖硫酸酯化修饰的最佳条件为V(氯磺酸)与V(吡啶)比例1:4、反应温度70℃、反应时间6h,此条件下取代度达到1.042;红外光谱分析表明,硫酸酯化后的葛仙米多糖具有硫酸酯键的特征吸收峰,其吸光度比值A1261/A1418与化学方法所测得的硫酸酯化取代度的相关系数达到0.974。红外光谱不仅可以表征硫酸酯化多糖的结构差异,还可定量硫酸基的取代度。 相似文献
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采用氯磺酸-吡啶法合成硫酸酯化米糠多糖,以取代度为指标,采用正交设计对硫酸酯化试剂比例,反应温度以及反应时间进行优化,通过傅立叶红外光谱分析酯化前后的结构。结果表明,米糠多糖硫酸酯化修饰的最佳条件为:氯磺酸和吡啶的体积比为1∶4,反应温度70℃,反应时间2 h,取代度达到1.29。红外光谱表明,硫酸酯化后的米糠多糖具有硫酸酯键的特征吸收峰。 相似文献
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响应面法优化木醋杆菌发酵酿酒丢糟水解液产细菌纤维素培养基及其产物性能 总被引:1,自引:0,他引:1
为提高木醋杆菌(Acetobacter xylinum)发酵酿酒丢糟水解液生产细菌纤维素(bacterial cellulose,BC)的产量,采用响应面法对发酵培养基进行了优化,同时比较了发酵产物BC的性能和结构。通过单因素及响应面试验结果确定木醋杆菌发酵酿酒丢糟水解液生产BC的最佳培养基配方为:蔗糖39.33 g、蛋白胨20.01 g、MgSO4 0.91 g、柠檬酸钠3.45 g、黄嘌呤1.02 g、乙醇10 mL、酒糟水解液1 000 mL、pH 6.0。在此条件下BC的产量为6.27 g/L,较优化前(4.4 g/L)提高了42.5%。利用傅里叶红外光谱、X射线衍射、扫描电子显微镜对发酵产物BC的性能和结构进行了比较,结果表明,酒糟水解液发酵产物BC结构性能与基本培养基发酵产物BC的基本一致,说明酒糟水解液能够替代部分发酵原料发酵生产BC,且不影响BC性能。 相似文献
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Chagas LM Rhodes FM Blache D Gore PJ Macdonald KA Verkerk GA 《Journal of dairy science》2006,89(6):1981-1989
The effect of increased access to pasture feeding during the last 6 wk of gestation on metabolic responses and postpartum anestrous interval was investigated. Heifers with a body condition score (BCS) of 5.0 (BC5+FF; on a 1-to-10 scale, US = 1.5 + 0.32 × New Zealand) were offered unrestricted pasture, and those with BCS 4.0 were fed either pasture unrestricted (BC4+FF) or restricted (BC4+RES) for the last 6 wk of gestation. After calving, all groups were offered unrestricted pasture. Mean BCS at calving for BC5+FF, BC4+FF, and BC4+RES were 4.7 ± 0.1, 4.3 ± 0.1, and 3.5 ± 0.1, respectively. At 35 d postpartum, LH pulse frequency was lower in BC4+RES than in BC4+FF and BC5+FF, which were similar. At 77 d after calving, 8% of BC4+RES cows had ovulated compared with 75% of BC4+FF and 69% of BC5+FF cows. Metabolic hormonal differences between BC4+FF and BC4+RES were not reflected in the differences between BC4+FF and BC5+FF for LH pulse frequency or ovulation. Unrestricted access to pasture during the final 6 wk of gestation for BC4 heifers reduced the risk of prolonged postpartum anestrus. Systemic factors, tissue sensitivity, and critical developmental set points are probably involved in the integrated control of ovulation by body condition. 相似文献
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为提高果汁发酵生产细菌纤维素的产量,开发特色纤维素功能性食品,以葡糖醋杆菌CGMCC 3917为实验菌种,以苹果汁和梨汁为发酵培养基生产细菌纤维素(BC),研究果汁用量和酵母膏添加量对细菌纤维素产量的影响,比较分析两种果汁生产的细菌纤维素在产量、结构和性质方面的差别。结果表明:梨汁发酵生产的细菌纤维素产量明显高于苹果汁,可达46.343g/100mL;其BC干膜复水率显著高于苹果汁,BC干膜的总糖含量稍高于苹果汁。两种果汁发酵生产的细菌纤维素在湿膜持水量及干膜的纤维素含量、蛋白质含量、脂肪含量以及微观结构上没有明显差异。 相似文献
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汉逊氏葡糖酸醋杆菌(Gluconacetobacter hansenii)利用传统Hestrin-Scharmm (HS)培养基发酵生产细菌纤维素(bacterial cellulose,BC)的过程中,普遍存在着BC产量不高、葡萄糖利用率低等问题。本研究首先比较了传统HS培养基和改良HS培养基发酵生产BC的结果,改良HS培养基中BC干重产量达到3.34g/L,较传统HS培养基提高了28%,但培养基废液中仍含有41%和70%的残糖和残氮;继而对改良HS培养基一次发酵废液进行优化,添加2.5 g/L酵母粉和1.8 g/L磷酸氢二钠,调节p H至5.9进行二次发酵,可获得3.16 g/L的BC干重,同时发酵液中副产物乙酸浓度仅为一次发酵的一半。综上,利用改良HS培养基发酵结合优化发酵废液进行二次发酵,共获得6.50 g/L的BC干重,是优化前的2.5倍以上,并且葡萄糖的利用率和转化率也分别由56.74%,22.86%提高至88.02%,36.87%。 相似文献
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为获得细菌纤维素(Bacterial cellulose,BC)高产菌株,同时改善BC材料学性能,采用低能N+离子束辐照技术对木醋杆菌(Acetobacter xylinum)进行了诱变选育。将菌落大小、光滑度、致密度、润湿度以及BC膜形成速率、柔韧度、BC产量等作为筛选依据,建立了平板-96孔板-试管筛选体系,筛选得到2株BC产量提高且产物材料学性能改良的目标菌株5D、2D。菌株5D BC产量为4.84 g/L,比出发菌株BC产量提高了89.06%,菌株2D BC产量为4.53 g/L,比出发菌株BC产量提高了76.95%。利用FT-IR、XRD、SEM、拉力试验等方法对目标菌株产物性能进行了研究,结果表明,目标菌株5D、2D发酵BC均具有高于出发菌株发酵BC的结晶度、抗拉强度及较小的断裂伸长率,具有更为致密的层状结构以及清晰的纤维束三维网状结构,表明其具有较为优良的力学性能。目标菌株的获得对BC产量的提高和性能改良奠定了基础。 相似文献
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为制备模拟细胞外基质结构的微纳尺度复合材料,利用静电纺丝技术制备了聚己内酯(Polycaprolactone,PCL)微米纤维膜,通过与纳米尺度的细菌纤维素(Bacterial Cellulose,BC)原位复合,制备了BC/PCL复合纤维支架。采用扫描电镜、红外光谱分析、X射线衍射分析对材料的形貌、结构进行了表征。通过单轴力学测试对复合材料力学性能进行了研究,并利用成纤维细胞对复合材料的生物相容性进行评价。结果表明:通过静电纺丝法制备的PCL微米纤维的平均直径,随聚合物纺丝液质量分数的增加有增加的趋势,BC与PCL微米纤维复合后,BC纳米纤维渗透入微米纤维膜内部,实现微纳米纤维较好的复合。红外光谱分析和X射线衍射分析进一步证明BC和PCL微米纤维成功复合。PCL微米纤维膜复合BC膜后,相比PCL微米纤维膜增加了其断裂强度,同时复合支架无明显细胞毒性,可应用于生物医学领域。 相似文献
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居间驹形氏杆菌发酵大豆糖蜜生产细菌纤维素条件的优化 总被引:1,自引:0,他引:1
通过居间驹形氏杆菌(Komagataeibacter intermedius CGMCC12562)发酵生产细菌纤维素,以大豆糖蜜作主要发酵原料,优化发酵工艺参数,提高细菌纤维素产量。在单因素试验的基础上,筛选出对细菌纤维素产量影响较大的4个因素,即大豆糖蜜可溶性固形物含量、玉米蛋白粉、ZnSO_4及苹果酸添加量,并通过Design-Expert响应面分析对这4个因素进行优化,得到最优的培养基及发酵工艺为:大豆糖蜜可溶性固形物含量14.13°Brix、玉米蛋白粉添加量1.6%、ZnSO_4添加量0.11%、苹果酸添加量0.41%;在30℃、接种量10%、装料量16%、初始pH 6.0的条件下静置培养7d,细菌纤维素产量高达(15.68±0.82)g/L。 相似文献
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Genetic and environmental relationships between body condition score and milk production traits in Canadian Holsteins 总被引:1,自引:0,他引:1
Loker S Bastin C Miglior F Sewalem A Schaeffer LR Jamrozik J Ali A Osborne V 《Journal of dairy science》2012,95(1):410-419
The objective of this research was to estimate genetic parameters of first-lactation body condition score (BCS), milk yield, fat percentage (Fat%), protein percentage (Prot%), somatic cell score (SCS), milk urea nitrogen (MUN), lactose percentage (Lact%), and fat to protein ratio (F:P) using multiple-trait random regression animal models. Changes in covariances between BCS and milk production traits on a daily basis have not been investigated before and could be useful for determining which BCS estimated breeding values (EBV) might be practical for selection in the future. Field staff from Valacta milk recording agency (Sainte-Anne-de-Bellevue, QC, Canada) collected BCS from Québec herds several times per cow throughout the lactation. Average daily heritabilities and genetic correlations among the various traits were similar to literature values. On an average daily basis, BCS was genetically unfavorably correlated with milk yield (i.e., increased milk yield was associated with lower body condition). The unfavorable genetic correlation between BCS and milk yield became stronger as lactation progressed, but was equivalent to zero for the first month of lactation. Favorable genetic correlations were found between BCS with Prot%, SCS, and Lact% (i.e., greater BCS was associated with greater Prot%, lower SCS, and greater Lact%). These correlations were strongest in early lactation. On an average daily basis, BCS was not genetically correlated with Fat% or MUN, but was negatively correlated with F:P. Furthermore, BCS at 5 and 50 d in milk (DIM) had the most favorable genetic correlations with milk production traits over the lactation (at 5, 50, 150, and 250 DIM). Thus, early lactation BCS EBV shows potential for selection. Regardless, this study showed that the level of association BCS has with milk production traits is not constant over the lactation. Simultaneous selection for both BCS and milk production traits should be considered, mainly due to the unfavorable genetic correlation between BCS with milk yield. 相似文献