Characterisation of volatile sulphur-containing compounds generated in crushed leaves of Chinese chive (Allium tuberosum Rottler)

To characterise the composition of sulphur-containing constituents in Chinese chive (Allium tuberosum Rottler), GC–MS and HPLC analyses were carried out, using 12 varieties of Chinese origin, 4 varieties of Japanese origin and 6 commercially available cultivars. Five disulphides (dimethyl, allyl methyl, methyl 1-(E)-propenyl, diallyl, and allyl 1-(E)-propenyl), two trisulphides (dimethyl and allyl methyl), and two vinyldithiins (3-vinyl-[4H]-1,2- and 2-vinyl-[4H]-1,3-) were identified on the basis of their mass spectral and GC-retention data. Among the detected sulphur compounds, sulphides with a methyl group predominated over those with an allyl group. This was supported by the HPLC estimations, suggesting that all cultivars examined had much greater amounts of methiin than alliin. Also, two novel compounds were tentatively identified as [3H,4H]-1,2-dithiin and [2H,4H]-1,3-dithiin on the basis of their mass spectral features, GC-retention data, and some experimental results on their formation in reaction mixtures with different proportions of methiin and alliin. Their formation mechanism was proposed.     

鳗鱼皮胶原蛋白水解物对结肠炎的改善作用

溃疡性结肠炎(UC)是一种特发性肠道疾病,发病率不断上升,且治疗药物都存在不同程度的副作用。研究发现胶原蛋白肽可缓解UC症状,并且安全、健康。然而,目前研究主要局限于UC的预防作用,缺少对其治疗作用的研究。鳗鱼皮富含胶原蛋白,而鳗鱼头一般在加工中被丢弃,造成资源浪费,目前缺少对鳗鱼皮胶原蛋白水解物的研究。本研究尝试利用鳗鱼头中的鱼皮提取胶原蛋白并进行水解,希望得到对UC具有治疗作用的鳗鱼皮胶原蛋白水解物(CH),提高鳗鱼加工副产物的利用价值。研究发现鳗鱼皮所含胶原蛋白丰富,占鱼皮湿重的27.87%,纯度较高且主要为Ⅰ型胶原蛋白,可作为胶原蛋白的优质来源。对胶原蛋白进行酶解,得到具有抗氧化活性的CH,并给药UC模型小鼠,结果显示:与阳性对照和模型组相比,CH可以安全健康地降低UC模型小鼠的DAI评分至0,并改善结肠状态;结肠组织病理切片表明CH可以恢复黏膜上皮完整性,减轻炎性细胞浸润;结肠组织氧化应激指标表明CH可以降低结肠组织MDA含量(0.75 nmol/mg pro)和MPO活性(0.11 U/g tissue),并通过提高GSH含量(22.92 umol/g pro)和SOD(693.61 U/g pro)、CAT(1.69 U/g pro)、GPx(141.29 U/g pro)3种抗氧化酶活性来提高结肠组织抗氧化能力,降低氧化应激水平,从而治疗UC。     

Effect of essential oil compounds and plant extracts on decay and termite resistance of wood

Essential oils and their derivatives have a long history of safe usage as antimicrobial agents in food industry. In this study various essential oils and extracts from plants were screened for their ability to inhibit wood decay and termite attack in laboratory decay and termite resistance tests using treated wood specimens. In the laboratory decay resistance tests, wood specimens treated with essential oil compounds were subjected to brown-rot fungus, Tyromyces palustris, and white-rot fungus, Trametes versicolor for three months. The specimens were also subjected to termite attack by subterranean termites, Coptotermes formosanus for three weeks in laboratory conditions. The formulation with cinnamaldehyde (DF3) was found to be effective against both the brown-rot and white-rot fungi used in the study. However, the formulation with cinnamic acid (DF8) was able to protect wood specimens against only the white rot fungus and about 50% mass loss occurred in the specimens subjected to the brown-rot fungus. The mass losses in the wood specimens treated with cassia oil containing formulation (DF4) showed that cassia oil was effective against both fungi. The wood tar oil and dodecanal compounds also inhibited fungal decay in the specimens. The wood specimens treated with the formulations used in termite resistance tests were more resistant against the termites when compared to specimens treated with the formulations in decay resistance tests. Even after severe weathering process, treated wood specimens showed resistance against the subterranean termites. Results suggest that essential oils and plant extracts might be important to develop new wood preservatives that are less harmful to the environment and humans than recently available ones.     

Isolation of antimicrobial agent from the marine algae Cystoseira hakodatensis

Cystoseira hakodatensis is an unutilised brown algae belonging to family Sargassaceae. A crude methanol extract from the algae showed inhibitory effects on the growths of Bacillus cereus and Bacillus licheniformis. To isolate the major antimicrobial agent, a sequential active‐guided isolation procedure was applied: liquid–liquid extraction, column chromatography and bio‐autography. A marked antimicrobial agent (active α) was isolated in hydrophobic fraction and was determined to phenolics without carbohydrates and proteins by phytochemical test. Regarding the antimicrobial potential, the isolated active α showed better inhibitory effects against B. cereus and B. licheniformis at 2 and 4 times of lower concentrations (62.5 and 31.3 μg mL^?1) in comparison with epigallocatechin gallate. These results showed that C. hakodatensis is a potential source of antimicrobial agent capable of preventing the growth of the two bacteria.     

啤酒酵母吸附重金属离子铬的研究

将啤酒酵母自制成生物吸附剂，用于吸附重金属离子铬，考察了啤酒酵母吸附Cr^3＋过程中的影响因素，即pH值、初始Cr^3＋质量浓度、吸附时间、菌体浓度及酸碱预处理方法等因素。结果表 明，啤酒酵母对Cr^3＋的吸附量随pH值的增加而增大，吸附的最佳pH值范围是4～7，当pH7时达到吸附最大值；随着初始Cr^3＋质量浓度增加，吸附量有所提高，当溶液初始Cr^3＋质量浓度为80mg／L吸附效果最佳；最佳吸附时间为1h；菌体的最佳浓度为50mg／L；及啤酒酵母经碱处理后吸附量增大：正交试验确定反应时间为反应过程的显著因素，确定啤酒酵母对Cr^3＋的吸附过程遵循Langmuir方程。     

Toxicity and tetramine contents of salivary glands from carnivorous gastropods

Salivary glands from 29 species of marine carnivorous gastropods in nine families were examined for lethal activity against mice and tetramine content. Mouse lethality was assayed by intravenous injection of buffer extracts into mice, and was detected in 14 species. Heat-stability tests confirmed that toxins in four species were thermolabile, while those in eight species were thermostable. Based on the tetramine contents determined by the colorimetric method using methanolic extracts, the thermostable toxins in seven species (Neptunea eulimatalamellosa, N. vinosa, N. arthritica, N. bulbacea, N. intersculpta f. pribiloffensis, N. intersculpta f. frater pilsbry and Hemifusus tuba) were considered to be tetramine contained at high levels (more than 900 micrograms/g salivary gland), but that in one species (Buccinum opisthoplectum) appeared to be a low-molecular-weight compound differing from tetramine. It is interesting that one (Hemifusus tuba) of the seven species containing high amounts of tetramine belongs to the family Melongenidae, although the other six Neptunea species are members of the family Buccinidae, as expected from previous studies.     

An investigation of the pH-activity relationships of Cex, a family 10 xylanase from Cellulomonas fimi: xylan inhibition and the influence of nitro-substituted aryl-beta-D-xylobiosides on xylanase activity

The kinetic parameters of Cex, a family 10 xylanase from Cellulomonas fimi, were determined at various pH levels using soluble birchwood xylan (BWX) as a natural polymeric substrate along with three other synthetic aryl-beta-D-xylobioside substrates. Using BWX, a high level of substrate inhibition was observed which increased with decreasing pH. In contrast, typical Michaelis-Menten-type profiles were obtained using the three aryl-beta-D-xylobiosides as substrates. The k(cat) values determined using o-nitrophenyl-beta-D-xylobioside did not change as the pH increased, whereas the k(cat) values obtained with BWX, phenyl-beta-D-xylobioside and p-nitrophenyl-beta-D-xylobioside decreased, suggesting that the presence of an ortho nitro group affects the activity displayed by Cex. These differences were not observed with XynB from Clostridium stercorarium F9, a member of the same family of xylanases as Cex. These results indicate that a careful evaluation is required when employing substituted aryl-beta-D-xylobiosides in the characterization of xylanases.     

Deletion and insertion of a 192-residue peptide in the active-site domain of glycosyl hydrolase family-2 beta-galactosidases

The monomeric multimetal-binding beta-galactosidase of Saccharopolyspora rectivirgula (srbg), a glycosyl hydrolase family-2 enzyme, has a unique sequence consisting of 192 amino acid residues with no similarity to known proteins. This 192-residue sequence (termed the "iota [iota] sequence") appears to be inserted into a sequence homologous to the active-site domain of the Escherichia coli lacZ enzyme (lacZbg). To assess the effects of the t sequence at specific sites of beta-galactosidase on the catalytic functioning and molecular properties of beta-galactosidase, deletion or insertion mutants of beta-galactosidases were constructed, expressed in LacZ- E. coli strains, and characterized: srbgdelta in which the iota sequence was deleted from srbg, and lacZbgI, in which the 192-residue iota sequence was inserted into the corresponding position (between Asp591 and Phe592) in the active-site domain of lacZbg. srbgdelta was a catalytically inactive, dimeric protein which retained multimetal-binding characteristics, suggesting that the iota sequence is very important for maintaining the structure necessary for the catalytic functioning and the monomeric structure of srbg but is not responsible for the unique metal ion requirements of srbg. On the other hand, lacZbgI existed as a mixture of a monomer, a tetramer, and higher multimers. The monomeric species was inactive, whereas the tetramer and other multimers were catalytically active (V(max )K(m) value, 25% of that of lacZbg) and highly specific for beta-D-galactoside. The tetrameric lacZbgI was activated by Mg2+ and Mn2+ with lowered metal affinities, and the stoichiometry of metal binding was unchanged from that of lacZbg. These results, along with the published stereo structure of lacZbg, suggest that, in lacZbgI, the inserted 192-residue iota peptide could fold independently of the lacZbg domains into a "sub-domain," lying distant from the active site and subunit interfaces.     

鳄鱼皮制革工艺的研究

主要从鳄鱼皮的粒面特点、形态结构及应用等方面出发 ,充分考虑了制革过程中机械磨耗对鳄鱼皮的作用 ,加强了对化工材料的选择 ,同时在灰碱烧鳞、漂色、鞣制、复鞣、染色、加脂、整饰等几个技术关键进行了细致的研究 ,提出了制造高档鳄鱼皮革的制革工艺。