小米黄色素的部分理化特性研究

对小米黄色素的稳定性和其抗菌活性进行了研究.结果表明小米黄色素水溶性较好,色素溶液对光、热比较稳定;在酸碱、金属离子、氧化剂、蔗糖等添加剂中具有较好的稳定性;但在含氧酸根阴离子、还原剂、维生素C、苯甲酸钠、山梨酸钾等添加剂中稳定性较差.抑菌活性实验表明,小米黄色素对金黄色葡萄球菌及大肠埃希氏菌都有一定的抑制作用.     

小米黄色素的部分理化特性研究

对小米黄色素的稳定性和其抗菌活性进行了研究.结果表明小米黄色素水溶性较好,色素溶液对光、热比较稳定;在酸碱、金属离子、氧化剂、蔗糖等添加剂中具有较好的稳定性;但在含氧酸根阴离子、还原剂、维生素C、苯甲酸钠、山梨酸钾等添加剂中稳定性较差.抑菌活性实验表明,小米黄色素对金黄色葡萄球菌及大肠埃希氏菌都有一定的抑制作用.     

微生物源溶菌酶的抑菌及抗炎活性

为研究微生物源溶菌酶对14 种供试菌的体外抑菌活性及对脂多糖（lipopolysaccharide,LPS）诱导的小鼠巨噬细胞RAW264.7 细胞炎症的抑制作用,该文采用二倍稀释法测定微生物源溶菌酶对供试菌的最小抑菌浓度（minimum inhibitory concentration,MIC）,评价其体外抑菌活性,通过构建LPS 诱导的小鼠巨噬细胞RAW264.7 炎症模型,以细胞中一氧化氮（nitric oxide,NO）及肿瘤坏死因子-α（tumor necrosis factor-α,TNF-α）的分泌量为指标,评价微生物源溶菌酶的抗炎活性。结果表明,微生物源溶菌酶对大肠杆菌、枯草芽孢杆菌、金黄色葡萄球菌、沙门氏菌、单增李斯特菌、耐热芽孢杆菌、酿酒酵母、酪丁酸梭菌、产黄青霉、黑曲霉和根霉11 种菌均表现出良好的抑菌效果,具有较强的广谱抑菌性;在试验浓度范围内,对保加利亚乳杆菌、嗜热链球菌、乳酸乳球菌乳亚种3 种益生菌无抑制效果,反而具有生长促进效果。微生物源溶菌酶对LPS 诱导的小鼠巨噬细胞RAW264.7 炎症模型表现出明显的抗炎作用,可显著降低NO 及TNF-α 的分泌,且与微生物源溶菌酶的作用浓度呈正相关。在试验浓度范围内,与模型组相比NO 分泌量最高可降低57.92%,TNF-α 分泌量最高可降低36.75%。微生物源溶菌酶具有良好的抑菌和抗炎活性,为其作为食品添加剂在抑制腐败菌生长、促进益生菌增殖等方面应用提供了理论基础。     

重组海参溶菌酶理化特性及生物活性的初步研究

将构建好的重组海参溶菌酶毕赤酵母菌株进行诱导表达,用CM52-纤维素阳离子交换柱分离得到电泳纯的重组海参溶菌酶.利用浊度法测定该酶的活性,滤纸片液体扩散法测定其抑菌谱.结果显示,重组海参溶菌酶的最适pH值为6.5,最适温度为35℃,在pH5.0～7.5、50℃以下有较好的稳定性.抑菌谱测定结果显示重组海参溶菌酶对6种指示菌均表现出抑菌性,尤其对副溶血弧菌的抑制作用最强.上述结果均与天然海参溶菌酶一致.     

茶红素的理化特性及生物学活性研究进展

茶红素是一类异质酸性酚类色素总称,作为茶叶发酵的产物,与茶汤的色泽、品质密切相关。文中针对茶红素形成途径、基本性质及可能结构进行了阐述,概括了目前茶红素分离纯化研究常用分析方法,综述了茶红素在抗氧化、抗癌、抗致畸、改善消化系统、抗毒素等生物学活性相关的研究进展。茶红素作为一种天然色素,在食品、化工和医疗保健行业都将有极大的发展应用前景。     

转基因羊奶表达重组人溶菌酶的急性毒性及 过敏性研究

利用乳腺生物反应器生产重组人溶菌酶蛋白,可以解决从天然材料中提取人溶菌酶来源稀少,质量难以保证等问题。为了保证食用安全,本文对转基因羊奶表达的重组人溶菌酶进行了急性毒性和致敏性评价。小鼠经口急性毒性试验结果显示,重组人溶菌酶对小鼠最大耐受剂量＞5000 mg/kg.BW,属实际无毒。体外模拟胃肠道消化试验结果显示,重组人溶菌酶在模拟胃液中2-30min内全部消化;在模拟肠液中15s－2min内全部消化;体外热稳定性试验结果显示,重组人溶菌酶在100℃加热60 min不会降解。综上所述,该重组人溶菌酶的毒性与过敏性风险较低,可以安全应用于食品行业。     

产Ⅱa类细菌素乳酸菌的筛选、鉴定与生物学特性的研究

使用牛津杯筛选法从发酵泡菜中筛选到1株对大肠杆菌、单核细胞增生李斯特氏菌、金黄色葡萄球菌和米曲霉具有抑制作用的乳酸菌BC-3,排除有机酸、H2O2干扰及蛋白酶处理失活,确定了抑菌物质为细菌素,发现该细菌素在pH5.0～12.0的条件下都有抑菌活性;在100℃热处理20min后活性基本不变。通过生理生化试验对该菌株进行了初步鉴定,结果显示,BC-3菌株归属为屎肠球菌(Entorococcus faecium),根据细菌素的一般分类原则将该细菌归类为IIa类细菌素。     

柠檬皮中柠檬苦素对黑曲霉的抑菌特性和机理

本研究以柠檬皮中柠檬苦素为原料,对其抑制黑曲霉的抑菌活性、抑菌活性的稳定性和抑菌机理进行了研究。结果表明:柠檬皮中柠檬苦素对黑曲霉的最小抑菌浓度(MIC)和最小杀菌浓度(MFC)分别为625μg/mL、5000μg/mL;对孢子萌发和菌丝生长抑制的半最大效应浓度(EC50)分别为311.03μg/mL和291.63μg/mL。柠檬苦素对黑曲霉的抑菌活性在紫外光照下受到抑制;在pH值为6～7时受到抑制;金属离子Fe3+、Fe2+可增强其抑菌活性。在柠檬皮中柠檬苦素作用下,黑曲霉的胞外碱性磷酸酶(AKP)活力、可溶性蛋白和菌丝体总糖含量发生很大变化;扫描电子显微镜观察发现黑曲霉孢子发生了变形、破裂、溶出物附着的现象。因此,柠檬苦素破坏了黑曲霉细胞壁和细胞膜的完整性,造成大量内容物渗出,影响了细胞正常代谢,进而抑制了菌体细胞的生长繁殖。     

金针菇不同极性部位的抑菌活性及稳定性

以金针菇粗提物的不同萃取相为材料,以大肠杆菌、产气杆菌、枯草芽孢杆菌、金黄色葡萄球菌、蜡状芽孢杆菌和啤酒酵母为供试菌,通过抑菌圈法和生长速率法探讨金针菇粗提物体外抑菌活性;并以金黄色葡萄球菌和大肠杆菌为供试菌,研究金针菇不同萃取相抑菌稳定性。结果表明,金针菇不同萃取相对金黄色葡萄球菌均有较强的抑制作用,乙酸乙酯相有显著的抑菌活性。同时,金针菇不同萃取相对革兰氏阳性菌的抑菌活性强于革兰氏阴性菌。金针菇不同萃取相对金黄色葡萄球菌的MIC范围是3.25 mg/m L~12.5 mg/m L,MBC范围是3.25 mg/m L~12.5 mg/m L。并且金针菇不同萃取相的抑菌活性对温度、紫外光的稳定性较好。可以作为一种保健食品(饮品)进一步开发利用。     

1株植物乳杆菌的生物学特性及体外抑菌活性研究

本研究以新疆和田地区维吾尔族母婴粪便为样品源,对其中乳酸菌（Lactic acid bacteria）进行分离鉴定。测定乳酸菌菌株对腹泻致病菌抑菌性能,及抑菌乳酸菌菌株的体外益生特征实验。依据groEL功能基因测序从19对母婴样本分离出属于15个种的113株乳酸菌,其中优势种是唾液联合乳杆菌（Ligilactobacillus salivarius）和香肠伴生乳杆菌（Companilactobacillus farciminis）。从113株乳酸菌菌株中筛选得到29株菌株对6种腹泻致病菌都有抑制效果,其中,香肠伴生乳杆菌HTb36X-2通过4 h的模拟胃肠液处理后存活率最高达69.50%;罗伊氏粘液乳杆菌（Limosilactobacillus reuteri）HTb34X5-6、HTb34X5-1自聚性最高与疏水性最高,其疏水性分别为31.67%和29.00%,自聚性分别为81.32%和70.91%;并结合抑菌菌株的抗生素耐药性和碳源代谢能力,最终筛选出香肠伴生乳杆菌HTb36X-2,副干酪乳酪杆菌（Lacticaseibacillus paracasei）HTb6X-6,干酪乳酪杆菌（Lacticaseibacillus casei）17X-4、17X-5,罗伊氏粘液乳杆菌HTb34X-5-1、HTb34X-5-6,发酵粘液乳杆菌（Limosilactobacillus fermentum）10D12-2 共7株作为潜在益生菌菌株,为开发具有抗腹泻功能的优良益生菌株及产品奠定前期基础。

     

Expression and bioactivity of recombinant human lysozyme in the milk of transgenic mice

Human milk lysozyme is an important protein for innate immunity, but human breast milk is a fairly poor source for commercial production of this enzyme. Research on the expression of recombinant human lysozyme (rHlys) is therefore potentially valuable to the dairy industry. In this study, 2 different kinds of transgenic mice, PBC-hLY and PBC-sighLY, were generated and used as system models to express rHlys. Six lines of PBC-hLY transgenic mice with human lysozyme genomic DNA-based constructs were generated, and a maximum expression level of rHlys approaching 0.154 mg/mL was achieved. Antibacterial activity of the whey from PBC-hLY female transgenic mice was determined by a turbidimetric assay. Results showed that antibacterial activity of the whey was strongly enhanced, and confirmed that rHlys retained full activity. For rHlys to be secreted efficiently into the milk of transgenic mice, 5 lines of mice were also generated, in which the signal peptide DNA of bovine β-casein was substituted for that of lysozyme in PBC-hLY transgenic mice. Compared with PBC-hLY transgenic mice, both the expression levels of rHlys and the antibacterial activity of the whey were much higher in the PBC-sighLY transgenic mice. The concentration of rHlys in one of these mice amounted to 1.405 mg/mL—3 times higher than the level in human whey. The antibacterial activity of the whey was also 3 times higher than that of human whey. The rHlys from both PBC-hLY and PBC-sighLY transgenic mice had the same antibacterial activity as human milk lysozyme. The effect of the signal peptide and copy numbers of the transgene on expression of rHlys was also evaluated. This work will certainly permit a better understanding of how mammary gland bioreactor systems can be applied to produce rHlys in other mammals, such as cattle.     

Production and processing of milk from transgenic goats expressing human lysozyme in the mammary gland

The potential for applying biotechnology to benefit animal agriculture and food production has long been speculated. The addition of human milk components with intrinsic antimicrobial activity and positive charge to livestock milk by genetic engineering has the potential to benefit animal health, as well as food safety and production. We generated one line of transgenic goats as a model for the dairy cow designed to express human lysozyme in the mammary gland. Here we report the characterization of the milk from 5 transgenic females of this line expressing human lysozyme in their milk at 270 μg/mL or 68% of the level found in human milk. Milk from transgenic animals had a lower somatic cell count, but the overall component composition of the milk and milk production were not different from controls. Milk from transgenic animals had a shorter rennet clotting time and increased curd strength. Milk of such nature may be of benefit to the producer by influencing udder health and milk processing.     

Use of human lysozyme transgenic goat milk in cheese making: effects on lactic acid bacteria performance

Genetically engineered goats expressing elevated levels of the antimicrobial enzyme lysozyme in their milk were developed to improve udder health, product shelf life, and consumer well-being. The purpose of this study was to evaluate the effect of lysozyme on the development of lactic acid bacteria (LAB) throughout the cheese-making process. Raw and pasteurized milk from 7 lysozyme transgenic goats and 7 breed-, age-, and parity-matched nontransgenic controls was transformed into cheeses by using industry methods, and their microbiological load was evaluated. The numbers of colony-forming units of LAB were determined for raw and pasteurized goat milk, whey, and curd at d 2 and at d 6 or 7 of production. Selective plating media were used to enumerate lactococcal species separately from total LAB. Although differences in the mean number of colony-forming units between transgenic and control samples in raw milk, whey, and cheese curd were non-significant for both total LAB and lactococcal species from d 2 of production, a significant decrease was observed in both types of LAB among d 6 transgenic raw milk cheese samples. In pasteurized milk trials, a significant decrease in LAB was observed only in the raw milk of transgenic animals. These results indicate that lysozyme transgenic goat milk is not detrimental to LAB growth during the cheese-making process.     

抗草甘膦转基因大豆对雄鼠睾丸生殖细胞与精子的影响

以雄性昆明鼠为实验动物,新生小鼠断乳后喂食抗草甘膦转基因大豆饲料,分别在30、60、90、120d取其睾丸和附睾,采用吉姆萨染色（Giemsa）检测小鼠睾丸组织早期精细胞微核率变化,并以荧光素标记的豌豆凝集素（FITC-PSA）检测小鼠附睾精子顶体完整率及顶体反应率变化。结果表明:与对照组相比,30、60、90、120d喂食抗草甘膦转基因大豆对小鼠睾丸组织早期精细胞微核率均无统计学差异,与之对应,30、60、90、120d喂食抗草甘膦转基因大豆对小鼠精子顶体完整率及反应率也无显著变化。研究表明:转基因大豆饲料30、60、90、120d喂食不会对小鼠睾丸组织染色体结构造成损伤,也未对小鼠精子的顶体形态结构和精子顶体反应能力造成影响。      

Characterization of N-linked oligosaccharides attached to recombinant human antithrombin expressed in the yeast Pichia pastoris

We studied the structures of four N-linked oligosaccharide chains of the recombinant human antithrombin (rAT) expressed in the yeast Pichia pastoris. rAT was fully glycosylated at Asn 96 and Asn 155, whereas the glycosylation on Asn 135 and Asn 192 was partial. The glycosylation level on Asn 135 was only 12% and this reduction is assumed to be one of the reasons for a higher heparin-binding affinity of rAT than plasma-derived human antithrombin (pAT). In order to determine the sizes and electrostatic charges of the N-linked oligosaccharides, rAT was treated with PNGase F, and the reduced ends were labelled by pyridylamination followed by analysis using anion exchange and amide adsorption columns. The N-linked oligosaccharides were 78% neutral and 22% phosphomannosylated. The neutral oligosaccharides were thought to be Man(9-12)GlcNAc(2) as their major components. The phosphomannosylated oligosaccharides were then subjected to mild acid hydrolysis and/or digestion with alkaline phosphatase, and their charge shifts were analysed by the affinity to an anion exchange column. Among phosphomannosylated oligosaccharides, monophosphate diester type was predominant, whereas negatively charged diphosphate diester and monophosphate monoester types were minor components. The mannose residues at the non-reducing end(s) of Man(9-12)GlcNAc(2) were phosphomannosylated or phosphorylated and these are the major components. Because rAT is less negatively charged than pAT, which has disialyl biantennary N-glycans, it might be less repulsive to pentasaccharide-bearing anticoagulantly active heparan sulphate proteoglycan molecules exposed on the surface of the damaged vascular vessels.     

Effects of yeast expressed recombinant interleukin-2 and interferon-gamma on physiological changes in bovine mammary glands and on bactericidal activity of neutrophils

The physiological effects of intramammary infusions of recombinant bovine cytokines in six lactating dairy cows on the quality and yield of milk and the bactericidal activity of milk neutrophils were investigated. Recombinant bovine interleukin-2 (rboIL-2) and interferon-gamma (rboIFN-gamma) were produced in the yeast Pichia pastoris. Two animals were given rboIL-2 (2 x 10(5) units) in two quarters, two animals were given rboIFN-gamma (6.5 x 10(5) units) in two quarters, and the other two cows received a dose of rboIL-2 in one quarter and rboIFN-gamma in a second quarter. In addition, each animal was given phosphate-buffered saline (PBS) in the other two quarters as a control. Somatic cell counts and conductivity of the fore milk were monitored before and after infusion. Neutrophils were isolated from quarter milk samples 36 h after infusion of cytokine or PBS and their bactericidal activities against Staphylococcus aureus were measured in vitro with a colorimetric assay. Quarters infused with rboIL-2 or rboIFN-gamma showed significant but transitory increases in both milk somatic cell counts and conductivity when compared with preinfusion values and with control quarters. There were minimal effects on daily milk yield. Neutrophils isolated from milk from quarters infused with rboIL-2 showed enhanced bactericidal activity against Staph. aureus. The bacterial killing from rboIL-2 treated quarters was significantly greater, with a mean of 63.5% compared with a mean of 5.4% for neutrophils taken from uninfected quarters to which PBS had been administered. The bactericidal activities for quarters treated with rboIFN-gamma and infected quarters treated with PBS were 15.0 and 30.0% respectively. The results indicate that intramammary infusions of rboIL-2 and rboIFN-gamma to lactating cows are well tolerated, and that rboIL-2 can activate milk neutrophils and augment their bactericidal activity.     

Pathological changes in bovine mammary glands following intramammary infusion of recombinant interleukin-2.

Eighteen lactating dairy cows were used to evaluate the physiological response of mammary glands to increasing doses of recombinant bovine interleukin-2. Right front and rear quarters were intramammarily infused with five different doses (.1 to 100 micrograms per quarter) of interleukin-2 as either a single or multiple treatment. Left front and rear quarters were intramammarily infused with a saline placebo and served as within-animal controls. Milk secretion samples for compositional analysis were collected from each quarter prior to infusion and at 12, 24, 36, and 48 h following infusion. Animals were slaughtered by exsanguination immediately following the 48-h sampling period, and mammary gland tissue was obtained for morphometric analysis. No changes in milk composition were observed between control quarters and those infused with up to 10 micrograms of interleukin-2 per quarter, administered as either a single or multiple treatment. Quarters infused with a single 100-micrograms dose of interleukin-2 or three consecutive doses of 25 and 100 micrograms of interleukin-2 had significantly lower lactose concentrations; there was a concomitant increase in bovine serum albumin, pH, and SCC compared with preinfusion concentrations or with control quarters. Morphometric analysis of tissue demonstrated an increase in stroma, a decrease in lumenal area, and a marked increase in the number of infiltrating leukocytes in those quarters infused with the higher doses of interleukin-2. Results suggest that interleukin-2 can be intrammammarily infused at doses as high as 10 micrograms per quarter without adversely affecting milk quality or normal mammary gland function.     

小鼠乳腺腺泡模型建立的初步探讨

建立乳腺腺泡模型和初步探讨其形成机理,为深入研究血乳屏障和泌乳机理提供基础方法和基本手段;采用改良的EHS基质培养法;成功获得具有极性和分泌功能的小鼠乳腺模型,向腺泡腔内可分泌β-酪蛋白和IGFBP-5;获得的小鼠乳腺腺泡模型具有显著的腔内分泌功能。     

转Bar、Bt基因双抗大米外源基因在食品加工过程中稳定性的研究

旨在了解转Bar、Bt基因双抗大米外源基因在酒酿和米果加工过程中的稳定性,以转Bar、Bt基因双抗大米为原料,进行了6种不同方式的加工,并针对其加工品中外源基因(包括CaMV35S启动子、Ubiquitin启动子、NOS终止子、Bar基因和Bt基因)进行不同大小片段的PCR扩增。结果表明,实验中长度小于200bp的片段均具有较高的GC含量(NOS终止子除外)和良好的稳定性。