低分子量壳聚糖及其衍生物的制备与溶菌酶对其降解的实验研究

将大分子质量壳聚糖用壳聚糖酶法降解成分子质量为3ku左右的低分子质量壳聚糖,再将其分别化学修饰成低分子质量的羧甲基壳聚糖和羧甲基甲壳素,并进行结构表征。在最适条件下,用溶菌酶分别对3种多糖进行降解实验,并进行酶解前后多糖的还原糖浓度测定和HPLC分析,确定溶菌酶对不同结构多糖的水解能力。结果表明,溶菌酶对羧甲基甲壳素水解作用最快,羧甲基壳聚糖次之,壳聚糖最慢。该研究为甲壳素衍生物在生物医用材料中的应用和降解速率调控提供了依据。     

针铁矿-四方纤铁矿-水体系氧同位素分馏的实验研究

针铁矿是非常重要的三价铁氧化物之一,其氧同位素组成对于古环境再造具有很大的价值。以4种不同的铁化合物作为Fe3+离子的源物质,于30～120℃范围内,采用强迫水解方法,在不同同位素组成的水中分别实验合成针铁矿和四方纤铁矿。结果表明,以Fe(NO3)3·9H2O、NH4Fe(SO4)2·12H2O、Fe(SO4)3·7H2O为Fe3+源物质合成的是纯针铁矿,而以FeCl3·6H2O为Fe3+源物质合成的是四方纤铁矿。氧同位素分析显示,在30～120℃范围内实验测定的针铁矿-水体系和四方纤铁矿-水体系氧同位素分馏几乎不可区分,并且满足下列分馏关系:103lnα针铁矿-水=9.59×103/T-26.39103lnα四方纤铁矿-水=8.85×103/T-24.44实验测定的针铁矿-水体系氧同位素分馏不仅与前人实验结果一致,而且与增量方法理论计算相近。由于实验采用不同反应途径得到了一致的分馏结果,因此所测定的针铁矿-水体系氧同位素分馏代表了热力学平衡。     

Al3+交换蛭石层间铝的赋存状态研究

利用阳离子交换实验方法,将天然蛭石转化为羟基Al3+型蛭石,通过X射线衍射、差热分析,研究铝离子在蛭石层间域中的赋存状态.结果显示,Al3+交换蛭石中的层间铝不能用KCl溶液将其提取出来,但可用柠檬酸钠溶液可以将其提取出来,是一种非交换性的聚合羟基铝.Al3+的离子电势虽然很高,但Al3+交换蛭石的脱水温度却低于蛭石原矿.表明Al3+进入蛭石层间域后发生水解反应,生成Al(OH)2+和Al(OH)2+从而降低了Al3+的有效离子电势,使其脱水温度降低.Al3+进入蛭石层间域后发生水解反应,其可能的水解反应式为[Al(OH2)6]3+〈=〉[Al(OH)x(OH2)6-x]3-x+xH+,其中x＜3.     

基于高通量测序技术解析鲣鱼(Katsuwonus pelamis)鱼油和鱼白调控肠道菌群结构作用

本研究利用高通量测序技术分析小鼠喂食鲣鱼(Katsuwonus pelamis)鱼油和鱼白酶解液后肠道微生物的多样性、群落组成以及结构的变化,探讨高蛋白、高脂肪饮食对人类健康的影响。研究结果显示:喂食鱼油组小鼠的肠道微生物丰富且多样。在门水平上,对照组和鱼油组的优势菌门为拟杆菌门(Bacteroidetes);鱼白组的优势菌门为厚壁菌门(Firmicutes)。在科水平上,对照组和鱼油组中的优势菌科为Muribaculaceae;鱼白组中的优势菌科为毛螺菌科(Lachnospiraceae)。在属水平上,对照组和鱼油组中的优势菌属为Muribaculum;鱼白组中的优势菌为Lachnoclostridium;对照组、鱼油组和鱼白组小鼠的肠道微生物群落中瘤胃球菌属(Ruminococcus)和拟杆菌属(Bacteroides)等丰度较高。在种水平上,对照组和鱼油组中的优势菌为Muribaculum intestinale;鱼白组中的优势菌为解糖梭菌(Clostridium saccharolyticum)。研究结果证明鲣鱼鱼油和鱼白可以调节菌群结构和组成,增加肠道有益菌,减少病原菌的丰度等。     

基于脲酶诱导碳酸钙沉积固化土体的研究进展

诱导碳酸钙沉积的土体固化是近年来岩土工程领域新兴起的新型环保地基处理技术, 该技术利用产脲酶菌的微生物诱导碳酸钙沉积（Microbially Induced Calcite Precipitation,即MICP技术）或基于脲酶的酶诱导碳酸钙沉积（Enzyme Induced Carbonate Precipitation,即EICP技术）,将松散的土体颗粒胶结成为整体,达到提高土体抗剪强度的目的。与MICP技术相比,EICP技术不存在生物安全风险,无需考虑是否有氧,且可适用于更小粒径土体的处理,因此具备广阔的实际工程应用前景。文章从脲酶类型与来源、EICP固化土体处理方法及EICP固化土体强度增长等方面,对近20年基于脲酶诱导碳酸钙沉积固化土体的研究进行了回顾与总结。     

DETERMINATION OF AMINO ACIDS IN TWO POLYSIPHONIA SPECIES AND STUDY OF ENZYMATIC HYDROLYSIS METHOD

The total content ot the nch amino acids in two common red algae, Potystpnoma urceolata and Polysiphonia japonica growing in the Qingdao seashore were determined. The algae powder was hydrolyzed by 6 mol/L HC1 at 110℃ for 48 h and determined by amino acid analyzer. The content was 25.35% and 24.16% , respectively, much higher than that of some other species. In addition, a nutritive liquid with abundant amino acids was prepared (by the enzymatic hydrolysis method using Polysiphonia urceolata ) as raw material for a kind of health beverage. The dried seaweed was decolored by 0.25% KMnO4 and 0.5% active carbon, then enzymalized. In the selection of enzymalizing condition, the orthogonal experimental design was used. Four factors including kinds of enzyme, quantity of enzyme, temperature and time were studied at 3 levels. According to the orthogonal design results, we can choose an optimal condition: hydrolyzing at 45℃ by neutral proteinase (0.25% , w/w) for 2 h, adjusting pH to 8.5, then adding trypsin (0.25% , w/w) and hydrolyzing for 2 h. Finally the above solution was alkalized by NaOH and neutralized by casein. After the hydrolyzed liquid was filtered and concentrated, suitable additives were added. The final products contain rich amino acids.     

响应面法优化香港巨牡蛎蛋白酶解工艺的研究

以水解度为指标,比较了6种蛋白酶对香港巨牡蛎(Crassostrea hongkongensis)的水解效果。在单因素考察实验的基础上,采用Box-Behnken模型响应面设计,建立香港巨牡蛎蛋白酶解的二次回归模型,确定最佳的水解条件。实验结果表明,海产品专用蛋白酶对香港巨牡蛎蛋白的水解效果优于其他蛋白酶,该酶的最佳水解条件为:酶与底物比为5.93%,酶解时间为4.07 h,酶解温度为54.6℃。在此条件下,海产品专用蛋白酶酶解香港巨牡蛎蛋白的水解度达到25.73%±2.39%。本研究为香港巨牡蛎的开发和利用提供了理论依据。     

对虾蛋白自溶制备ACE抑制肽的工艺条件优化

以凡纳滨对虾为原料,以ACE抑制率为指标,利用响应面法对虾肉蛋白自溶制备ACE抑制肽的工艺条件进行了优化,即在酶解条件(pH值、温度、虾头虾肉质量比)和ACE(Angiotensin I-converting Enzyme,ACE)抑制率之间建立了数学模型Y=23.59-0.21X1+0.84X2+0.85X3-0.71X12-0.94X22-1.06X32+0.088X1X2-0.46X1X3-0.87X2X3。分析表明,在3个因素中,虾头与虾肉比例对ACE抑制率的影响最为显著。优化后的工艺参数为:pH7.35,温度57.2℃,虾头与虾肉比例为1∶1。根据回归方程的预测结果,反应时间为4 h,其ACE抑制率达41.9%。     

Alkyl nitrates and bifunctional nitrates of atmospheric interest: Henry's law constants and their temperature dependencies

Henry's law coefficients of 15 alkyl nitrates, keto-, hydroxy-, and dinitrates of atmospheric interest have been measured, mostly over the temperature range 1–25°C. The compounds are stable in aqueous solution. Where literature data were available, Henry's law coefficients are in very good agreement. It is concluded that dissolution in cloud and rain water is not an important loss process for alkyl mononitrates in the atmosphere. The residence times of the more soluble bifunctional organic nitrates, however, are significantly affected or even controlled by washout and rainout. Gas chromatographic analysis of bifunctional nitrates in preconcentrated atmospheric samples may be adversely affected by the adsorptive properties of these compounds.