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酶法降解壳聚糖工艺研究 总被引:1,自引:0,他引:1
采用非专一性酶(溶菌酶、纤维素酶)和专一性酶(壳聚糖酶)降解壳聚糖,探讨了不同条件对壳聚糖降解的影响.结果表明,溶菌酶降解壳聚糖的最佳条件为反应时间3.0 h、反应温度50℃、pH值4.0、酶用量40 U·mL-1;纤维素酶降解壳聚糖的最佳条件为反应时间1.5 h、反应温度55℃、pH值5.5、酶用量40 U·mL-1;壳聚糖酶降解壳聚糖的最佳条件为反应时间2.0 h、反应温度45℃、pH值5.0、酶用量30 U·mL-1.对壳聚糖酶酶解产物进行HPLC分析,发现得到了分子量分布较窄的壳寡糖. 相似文献
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在简单均相体系下.研究了壳聚糖及丁二酸酐酰化壳聚糖在双氧水中的降解特性。采用鸟氏粘度计,利用一点法测量了降解过程中壳聚糖及丁二酸酐酰化壳聚糖的分子量,讨论了该体系下壳聚糖及丁二酸酐酰化壳聚糖的降解速率.通过红外光谱分析了双氧水对低分子量壳聚糖和低分子量丁二酸酐酰化壳聚糖结构的影响。结果表明.在该体系下·壳聚糖及丁二酸酐酰化壳聚糖的降解主要发生在反应开始后的2~3h内.此后降解产物的分子量逐渐趋于20000;相同条件下,丁二酸酐酰化壳聚糖的降解程度高于壳聚糖;红外光谱表明.采用该降解体系制备的降解产物主链结构基本没有发生变化。 相似文献
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将壳聚糖进行液态均相配合反应制得壳聚糖锰配合物,IR、元素分析及热分析等检测证实了壳聚糖锰配合物中配位键的存在,且显示壳聚糖锰配合物存在有利于壳聚糖高分子链断裂的弱势结构。以H2O2对壳聚糖.Mn(Ⅱ)配合物及壳聚糖进行氧化降解,考察降解过程中粘度的变化及降解产物分子量分布,在相同的降解条件下,壳聚糖锰配合物的降解速度明显高于壳聚糖,且降解产物分子量分布较壳聚糖直接降解窄。对壳聚糖锰配合物降解反应动力学研究表明壳聚糖锰配合物对H2O2分解不存在催化作用,其降解反应与壳聚糖的差异只与其结构有关。对降解产物进行脱金属处理,所得低聚壳聚糖含锰量为0。 相似文献
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木瓜蛋白酶降解壳聚糖的研究 总被引:1,自引:0,他引:1
通过正交实验法和线性回归法对木瓜蛋白酶降解壳聚糖进行了研究,详细分析了脱乙酰度、酶用量、pH值、温度4个因素对壳聚糖降解产物粘度的影响,从而获得降解2g壳聚糖的最佳反应条件为脱乙酰度为66%、0.002g/mL木瓜蛋白酶为20mL、pH值4.8和温度67℃。 相似文献
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利用纤维素酶催化水解壳聚糖的研究 总被引:5,自引:0,他引:5
利用纤维素酶催化降解壳聚糖,分别研究了pH值、温度、酶/糖及反应时间等因素对壳聚糖相对分子质量的影响,得到的最佳反应条件为:pH为5.6、n(酶)/n(糖)为0.1/1.0、反应温度为50℃、反应时间为6h。用纤维素酶催化降解壳聚糖只能得到最低平均相对分子质量为18000的低聚壳聚糖。为了得到更低相对分子质量的壳聚糖,在壳聚糖酶降解后加入一定量双氧水继续降解。研究了双氯水加入量及加入时间的影响,最终可得到平均相对分子质量为1500的低聚壳聚糖。 相似文献
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壳聚糖是迄今为止发现的天然多糖中唯一的碱性多糖,将壳聚糖降解到需要的分子量是其应用的前提。本文综述了壳聚糖化学降解(酸降解和氧化降解)、物理降解(辐射降解、超声波和微波降解、机械研磨降解、高压均质降解)、酶降解(专一性酶降解、非专一性酶降解、复合酶降解)以及复合降解法的最新进展,供相关领域人员参考。 相似文献
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M. S. J. Simmonds W. M. Blaney F. Delle Monache M. Marquina Mac-Quhae G. B. Marini Bettolo 《Journal of chemical ecology》1985,11(12):1593-1599
Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria. 相似文献
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Cheng-Le Zhao Shane Porzio Alan Smith Haiyan Ge H. T. Davis L. E. Scriven 《Journal of Coatings Technology and Research》2006,3(2):109-115
Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively.
There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized.
High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without
the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of
fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to
achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic
SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve
F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender
particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing,
and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing
or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually
preserves suspension stability during freezing.
Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago,
IL. Tied for first place in The John A. Gordon Best Paper Competition. 相似文献
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Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US
In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae
and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted
in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures
(release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species
(Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species
to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were
exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of
separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles
from the southeastern region of the US. 相似文献
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Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed. 相似文献
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中蓝晨光化工研究院有限公司《塑料工业》编辑部 《塑料工业》2009,37(3)
收集了2007年7月~2008年6月世界塑料工业的相关资料,介绍了2007~2008年国外塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况.按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、特种工程塑料(聚苯·硫醚、液晶聚合物、聚醚醚酮)、通用热固性树脂(酚醛、聚氨酯、不饱和聚酯树脂、环氧树脂)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍. 相似文献
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中蓝晨光化工研究院《塑料工业》编辑部 《塑料工业》2007,35(3):1-25,67
收集了2005年7月~2006年6月国外塑料工业的相关资料,介绍了2005—2006年国外塑料工业的发展情况。提供了世界塑料产量、消费量及全球各类树脂生产量以及各国塑料制品的进出口情况。作为对比,介绍了中国塑料的生产情况。按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(聚酰胺、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、通用热固性树脂(酚醛、聚氨酯、不饱和树脂、环氧树脂)、特种工程塑料(聚苯硫醚、液晶聚合物、聚醚醚酮)的品种顺序,对树脂的产量、消费量、供需状况及合成工艺、产品开发、树脂品种的延伸及应用的扩展作了详细的介绍。 相似文献