啤酒糟蛋白水解物对金黄色葡萄球菌抑菌能力研究

选择4种蛋白酶制备出不同时间水解的啤酒糟蛋白水解物,分别检测其对金黄色葡萄球菌的抑菌能力。结果表明:采用Flavourzyme水解180min的水解物具有较好的抑制金黄色葡萄球菌的能力;采用聚酰胺柱层析、离子交换柱层析方法及凝胶柱层析方法对水解物进行分离测定,得到分子量约为1 877.67的啤酒糟多肽样品,其对于金黄色葡萄球菌的最小抑菌浓度为2%。     

海洋假单胞菌GY-1菌株的抗菌作用及其胞外抗菌蛋白的分离纯化

采用对峙培养法和牛津杯法测定海洋假单胞杆菌(Pseudomonas) GY-1菌株和发酵液的抑菌作用。结果表明：GY-1菌株和发酵液对小麦根腐病菌(Bipolaris sorokiniana)、禾谷镰刀病菌(Fusarium graminearum)、菠菜早疫病菌(Alternaria solania)、斑点落叶病菌(Alternaria alternata)、油菜菌核病菌(Sclerotinia sclerotiorum)和小麦叶枯病菌(Alternaria tenuis Nees)等植物病原真菌有较强的抑制作用。发酵液采用硫酸铵分级沉淀、DEAE Sepharose Fast Flow柱层析、Sephadex G-75凝胶层析,以小麦根腐病菌为指示菌进行活性追踪和SDS-PAGE电泳纯度跟踪检测,纯化出一种对小麦根腐病菌具有明显抗菌作用的抗菌蛋白,其分子质量约为70.9kD。     

金黄色葡萄球菌肠毒素B的分离纯化

为了分离纯化金黄色葡萄球菌肠毒素B(SEB),在离心、浓缩后,将浓缩液依次经羧甲基阳离子交换纤维素CM-32和葡聚糖凝胶G-75两步柱层析,再经SDS-聚丙烯酰胺凝胶电泳分析,获得了电泳纯的金黄色葡萄球菌肠毒素B.实验证明,该简化的二步柱层析分离得到的SEB纯度高,方法简便易行,一般实验室均可采用.     

球等鞭金藻胞内和胞外多糖的分离纯化及其抑菌活性

采用分级沉淀、Sephadex G-75凝胶柱层析和DEAE-52离子交换柱层析对球等鞭金藻胞内粗多糖(IPS)进行分离;对胞外粗多糖(IEPS)则进行Sephadex G-100凝胶柱层析分离。在此基础上,分析所获多糖组分对大肠杆菌、枯草芽孢杆菌、金黄色葡萄球菌和变形杆菌等细菌的抑菌活性。同时,通过紫外光谱和红外光谱测定,比较IPS和IEPS结构的异同。结果表明：IPS和IEPS均具有抑菌活性,前者抑制大肠杆菌、枯草芽孢杆菌和金黄色葡萄球菌的生长,后者抑制大肠杆菌和枯草芽孢杆菌的生长;IPS经DEAE-52纤维素柱层析分离,获得2个多糖组分：IPSⅠ和IPSⅡ。IEPS经Sephadex G-100凝胶柱层析分离,获得3个多糖组分：IEPSA、IEPSB和IEPSC。活性检测表明,IPSⅠ和IPSⅡ抑制枯草芽孢杆菌和金黄色葡萄球菌的生长;IEPSA、IEPSB和IEPSC抑制大肠杆菌的生长;紫外光谱表明,IPS和IEPS均不含核酸、游离或裸露的蛋白质和色素;IPS和IEPS的红外光谱比较相似,以半乳糖为构架,均含有酰氨取代基,但不同之处在于,后者不含硫酸取代基。     

浒苔多糖和硒化浒苔多糖抑菌作用研究

从浒苔中提取浒苔多糖,并进行硒化反应,制备硒化浒苔多糖。考察了浒苔多糖和硒化浒苔多糖对金黄色葡萄球菌、大肠杆菌2种细菌和柑桔炭疽病菌、苹果腐烂病菌、棉花枯萎病菌、苹果轮纹病菌、小麦全蚀病菌、黄瓜枯萎病菌、苹果斑点落叶病菌等7种植物致病真菌的抑菌特性。结果表明:硒化浒苔多糖和浒苔多糖对大肠杆菌、金黄色葡萄球菌都有一定的抑菌作用,硒化浒苔多糖的抑菌效果要明显优于浒苔多糖,最小抑菌浓度分别为1.70mg/mL和6.80mg/mL;硒化浒苔多糖对黄瓜枯萎病菌、苹果斑点落叶病菌、棉花枯萎病菌和小麦全蚀病菌4种致病真菌有较好的抑菌效果,但浒苔多糖对供试真菌几乎没有抑菌效果。     

藿香内生真菌次级代谢产物抗菌活性研究

【目的】分离纯化藿香花中内生真菌,测定内生真菌次级代谢产物抑菌活性。方法采用组织分离法从藿香花中分离内生真菌,根据显微形态结构进行初步鉴定;用微量肉汤稀释法测定藿香内生真菌次级代谢产物的最低抑菌浓度(MIC)。结果从藿香茎中共分离得到13株内生真菌,鉴定出12株,分别属于丝核菌属、黑孢霉属、长蠕孢菌属、短蠕孢菌属、丝孢菌属、链格孢菌、镰刀菌属、头孢霉属。大多数藿香内生真菌次级代谢产物的乙酸乙酯部位具有抗菌活性。菌株H-2的乙酸乙酯部位抑菌活性最强,对六种供试菌的MIC均为250μg/mL。菌株H-9的乙酸乙酯部位对无乳链球菌的抑制活性最好,为31.25μg/mL,对其他供试菌在500μg/mL能够表现出抑制活性。结论藿香内生真菌的次级代谢产物具有抑菌活性,为进一步的活性指导分离提供了理论依据。     

银杏种仁蛋白分离纯化及其抑菌活性

从银杏种仁中分离纯化具有抑菌活性的蛋白质,并分析其抑菌活性。结合抑菌活性分析,采用硫酸铵分级盐析、透析、纤维素DE-52阴离子交换柱层析及Sephadex G-75凝胶过滤柱层析对银杏种仁蛋白（Ginkgo bilobaseed protein,GBSP）进行分离纯化,得到一种抑菌蛋白GBSPⅠ-A。十二烷基磺酸钠-聚丙烯酰胺凝胶电泳（sodiumdodecyl sulfate polyacrylamide gel electrophoresis,SDS-PAGE）检测结果显示,该蛋白呈单一条带,其分子质量约为42.80 kD;Superdex G-75柱层析结果显示GBSPⅠ-A呈单一对称峰,高效凝胶渗透色谱测定其分子质量为39.32 kD;该蛋白对肺炎克雷伯氏菌、金黄色葡萄球菌、戴尔有孢圆酵母及黑曲霉的最小抑菌浓度（minimum inhibitory concentration,MIC）分别为20、20、20、12 mg/mL。     

含银离子抗菌纤维的抗菌性能研究

以大肠杆菌和金黄色葡萄球菌为实验菌种,用抑菌晕法、定时暴露法和振荡摇瓶法时自制的含Ag＋抗菌纤维的抗菌性能进行了研究和评价。实验表明,含Ag＋抗菌纤维对大肠杆菌和金黄色葡萄球菌具有很好的抗菌性能：经过10次洗涤之后,对大肠杆菌的菌数减少率在95％以上,对金黄色葡萄球菌的菌数减少率在80％以上。     

链霉菌 CSDX076次级代谢产物Pseurotin A的分离及结构鉴定

对从赤水丹霞山土壤样品中分离得到的链霉菌(Streptomyces sp.)CSDX076进行液体发酵。利用乙酸乙酯萃取,硅胶柱层析、薄层层析和反相中压柱层析对发酵液中的次级代谢产物进行分离、纯化;通过核磁共振法对纯化的分离产物进行结构鉴定。结果表明,该研究从链霉菌属中成功分离得到次级代谢产物Pseurotin A。采用滤纸片法对Pseurotin A进行抗菌活性测试,Pseurotin A对金黄色葡萄球菌具有抑制作用,其抑菌圈直径为5.0 mm。     

车前草提取物抗菌活性的研究

采用滤纸片扩散法对车前草的60%vol﹑70%vol﹑80%vol﹑90%vol乙醇提取物及石油醚﹑氯仿﹑正丁醇和水相萃取物对4种细菌和13种真菌进行抗菌活性研究。结果表明:车前草粗提物对金黄色葡萄球菌、大肠杆菌、青霉和假丝酵母等常见食物致病菌的抑制作用显著,对常见植物病原菌苹果腐烂病菌、黄瓜枯萎病菌、烟草赤星、草莓镰刀菌、番茄灰霉等的抑制作用也较好。     

Protein extraction from pasture: Effect of crop species and of a reducing agent on the quality of extracted protein

Leaf protein concentrations (LPC) were prepared from herbage harvested from pure stands of ryegrass (Lolium perenne), white clover (Trifolium repeens), lucerne (Medicago sativa cv. Wairau) and from a stand of ryegrass/white clover dominant pasture: each crop was processed with and without the addition of sodium metabisulphite just prior to pulping. Protein quality was measured by rat growth and in-vivo rat true digestibility. Juice protein composition was measured and was related to chemically available lysine and protein true digestibility. Protein in ryegrass LPC had a lower digestibility (72%) than that from white clover (81%) or lucerne (78%), due to a higher proportion of the juice true protein being from the chloroplastic fraction for ryegrass (73%) compared with the two legumes (49–56%). The chloroplastic fraction is of inherently lower digestibility than the cytoplasmic fraction. Metabisulphite treatment at pulping caused a small but consistent increase of chemically available lysine in the LPC, and also improved chemically available methionine and protein utilisation for growth. Effects on protein true digestibility were inconsistent. When LPC was fed with a methionine supplement, the efficiency of utilisation of protein for growth did not differ amongst the four crops. This occurred despite the true digestibility of protein on LPC being higher for the legumes than for ryegrass and ryegrass/white clover.     

Variations of cellular nitrogen components of different yeasts during growth

The amino acid composition of whole cells of eight yeast species together with protein and RNA contents were determined at three selected points of a growth curve. Total nitrogen and crude protein contents showed a decrease during the growth cycle, while true protein concentrations appeared to be more stable. RNA contents decreased in the stationary phase. Variability was negligible for overall amino acid patterns from different phases of growth.     

Relationships between protein and energy consumed from milk replacer and starter and calf growth and first-lactation production of Holstein dairy cows

The objective was to determine relationships between protein and energy consumed from milk replacer and starter and calf growth and first-lactation production of Holstein heifer calves. Milk replacer and starter protein intake and metabolizable energy (ME) intake data were collected from 4,534 Holstein heifer calves for growth and 3,627 Holstein cows for production from birth year of 2004 through 2014. Calves from 3 commercial dairy farms were assigned to 45 different calf research trials at the University of Minnesota Southern Research and Outreach Center, Waseca, Minnesota, from 3 to 195 d of life. Calves were moved to heifer growers at 6 mo of age, and calves were returned to their farm of birth a few weeks before calving. Most calves (85%) were fed a 20% crude protein and 20% fat milk replacer at a rate of 0.57 kg/calf daily. Metabolizable energy and protein consumed from milk replacer and starter were calculated for each individual calf for 6 and 8 wk of age. Mixed model analyses were conducted to determine the effect of protein and energy consumed from both milk replacer and starter on calf growth and first-lactation 305-d production of milk, fat, and protein, adjusting for herd, season of birth, year, average daily gain (ADG), and calf trial. Calves with ADG >0.80 kg/d consumed more combined protein and ME than calves with lower ADG. Protein and ME intake from calf starter affected growth more than protein and ME intake from milk replacer because most calves were fed the same fixed amount of milk replacer. Calves born during the fall and winter had greater combined protein and ME intake than calves born during the spring and summer. Milk replacer protein and ME intake did not have a relationship with first-lactation 305-d milk, fat, and protein production. However, starter protein and ME intake during the first 6 and 8 wk of age had a significant positive relationship with first-lactation 305-d milk, fat, and protein production. Consequently, combined protein and combined ME intake had a positive effect on 305-d milk, fat, and protein production. Variance in protein and ME intake was high, suggesting that additional factors affect calf growth during the first 8 wk of life and milk production in first lactation.     

Association of growth hormone loci with milk yield traits in Holstein bulls

A pedigree analysis was used to investigate the association of bovine growth hormone loci with milk production traits of Holstein cattle. Holstein bulls were typed for three bovine growth hormone loci located in exon V, intron C, and the 3' region of the gene. Phenotypic data were daughter yield deviations for milk, fat, and protein yields and for fat and protein percentages. Analysis of linkage across families was applied to the data using one or two bovine growth hormone loci as markers linked to a putative biallelic quantitative trait locus. Estimated parameters were allele frequency, genotypic means, within-genotype standard deviation of a putative quantitative trait locus, and recombination fraction between the markers and the quantitative trait locus. Parameters were estimated by maximum likelihood techniques. The estimated frequency of the quantitative trait locus allele that decreased the value of the phenotype ranged from 0.1 for milk yield to 0.6 for protein yield. The estimated effect of an allele substitution at the quantitative trait locus, given in phenotypic standard deviation units, ranged from 0.75 for fat percentage to 1.6 for milk yield. The standard deviation within genotype ranged from 0.67 for fat yield to 0.87 for milk yield. The estimated recombination fraction was close to zero for protein percentage, indicating physical linkage between a quantitative trait locus affecting the trait and the bovine growth hormone loci.     

Mammary-derived growth inhibitor protein and messenger ribonucleic acid concentrations in different physiological states of the gland.

Expression of mammary-derived growth inhibitor in tissue from lactating and involuting bovine mammary glands was investigated. Seventeen lactating, pregnant (220 to 272 d in gestation) cows were divided in two groups of 8 and 9 cows each. Cows of the first group were slaughtered while in lactation. Cows of the second group (9 involuting cows) were slaughtered at 13 to 52 d following sudden cessation of milking. High concentrations of mammary-derived growth inhibitor (.63% of the total protein) were detected in mammary tissue of lactating cows. Mammary-derived growth inhibitor (less than .10% of the total protein) was dramatically reduced during most of the involution period (13 to 45 d following cessation of milking). Mammary-derived growth inhibitor was again detected (.28% of the total protein) during the last stage of the involution (46 to 53 d after cessation of milking), which coincided with colostrum formation. When steady state concentrations of mammary-derived growth inhibitor mRNA were examined, the results obtained mirrored those obtained at the protein concentration. These data suggest that regulation of mammary-derived growth inhibitor occurs via modulation of the steady state concentration of its mRNA. Furthermore, there is a strong correlation between mammary-derived growth inhibitor expression and lactation in dairy cows.     

氮浓度对异养小球藻生长及蛋白质含量的影响

为了提高异养小球藻蛋白质含量低的问题,研究了异养小球藻生长及蛋白质含量和氮浓度的关系,探究了分阶段调控氮浓度对异养小球藻生长及蛋白质含量的影响。结果表明,氮浓度在3～15mmol/L范围内,小球藻生物量及蛋白质含量随氮浓度增加而增加,生物量从0.91g/L提高到了3.02g/L,蛋白质含量从26.1%提高到了37.4%。分阶段培养小球藻,首先在低氮条件下培养至指数期前期,然后转移至高氮浓度下培养,生物量达3.04g/L,且蛋白质含量提高至53.8%,与自养培养条件下蛋白质含量相当。     

Plasmin levels in fresh milk whey and commercial whey protein products

Growth of psychrotrophic bacteria in nonfat dry milk at refrigeration temperatures was shown previously in our laboratory to cause a shift in plasmin (a native milk protease) from the casein to the whey fraction. The whey fraction from cheesemaking is commonly used to make whey protein concentrates and isolates, which then are used as functional ingredients in various food systems. Plasmin activity in whey protein products may cause breakdown of food proteins to have desirable or undesirable effects on food quality. This raised questions about the level of plasmin in commercial whey protein products and factors that affect this plasmin level. Therefore, the objectives of this study were to determine: 1) plasmin concentrations in sweet and acid whey protein products as influenced by Pseudomonas growth during storage of fresh milk, and 2) plasmin concentrations in commercial whey protein products. Whey type (sweet or acid) had a significantly (P < 0.05) greater effect on whey-associated plasmin activity than did Pseudomonas fluorescens M 3/6 growth. Acid whey protein products had significantly (P < 0.05) higher plasmin concentrations than sweet whey. Plasmin activities associated with acid and sweet whey protein products were both significantly (P < 0.0001) affected by the growth of Pseudomonas fluorescens M 3/6. The interaction effect between bacterial growth and whey type on plasmin activity was not significant (P = 0.2457). Plasmin activity in the reconstituted commercial whey protein concentrates (i.e., sweet and acid) varied considerably (16.3 to 330 micrograms/g of protein), but was significantly lower (2.1 to 4.4 micrograms/g of protein, P < 0.05) in whey isolates. These quantitative data were supported by plasmin activity visualized by casein SDS-PAGE.     

FOOD PROTEIN FROM MEAT AND BONE MEAL

SUMMARY— Studies were undertaken to develop a nutritious and aesthetically attractive protein concentrate from commercial meat and bone meal. Flotation in carbon tetrachloride was used to separate meat residues from the bulk of the bone. The meat residues had moderate nutritional merit in rat feeding trials. Further improvement was achieved by size separation or by base extraction. The finer fraction from size separation had a more favorable amino acid balance and gave better growth rates and protein efficiency ratios (PER) than did the unfractionated material. Growth rates increased markedly as the amount in the diet was increased to give 15 and 20% protein. It had more than an additive effect on growth and PER as a supplement to wheat flour or whole corn. Extraction with base improved amino acid balance, growth response and flavor. Addition of 9% of the base-extracted material to rice or biscuits had little effect on flavor; a gray-red color remained prominant. Overall yields of the base-extracted material starting with meat and bone meal were about 34%. The protein content of the product was about 88% on a dry weight basis. Its PER when 2% methionine was added was 75% of that of casein (without added methionine) in a rat feeding experiment. The cost of production is estimated at about $0.13/lb when allowance is made for methionine addition and for sale of residues from the production process as an animal feed supplement     

Dilution of Cow's Milk and Egg Proteins with Glutamic Acid and the Effect on the Protein Efficiency Ratio

SUMMARY– The effect of dilution of egg proteins and cow's milk proteins with varying levels of L-glutamic acid (GA) on the growth of young rats and protein efficiency ratio of the blends was studied. Addition of glutamic acid to diets containing 8.5% to 5.0% egg proteins to maintain the nitrogen content of the diet constant at 1.6% (equal to 10% protein) did not cause any increase in the growth rate of rats as compared to that on corresponding diets without added glutamic acid. The protein efficiency ratios progressively decreased from 4.74 for 10% egg protein diet to 2.88 for 5% egg protein + 8.4% glutamic acid diet. Addition of glutamic acid to diets containing 8.5 to 5.0% milk proteins to maintain the nitrogen content of the diet constant at 1.6% level caused a significant decrease in the growth rate as compared to that on corresponding diets without added glutamic acid. The protein efficiency ratios also progressively decreased from 3148 for 10% milk proteins to 1.46 for a mixture of 5% milk proteins + 8.4% glutamic acid. The results show that both egg proteins and milk proteins contain adequate amounts of non-essential amino acids for maximum utilization of essential amino acids present in them for the growth of young rats.     

毁灭炭疽菌诱抗蛋白的分离纯化及对烟草抗病促生作用

为明确诱抗蛋白能够对烟草产生抗病促生作用,采用加热、离心、硫酸铵分级沉淀、透析和凝胶色谱柱等方法,从毁灭炭疽菌（Colletotrichum destructivum）中分离纯化出一种诱抗蛋白,并采用喷雾接种和摩擦接种的方法研究其预防保护作用。结果表明,经SDS-PAGE显示该诱抗蛋白分子量约为38kD,且目的蛋白存在于Pro-P2-TX组份中;对烟株进行烟草普通花叶病毒病的接种试验,接种3d后,诱抗蛋白处理组烟草叶片枯斑数明显少于清水对照组,对TMV的诱抗效果为73.79%;该诱抗蛋白能够明显促进烟草的生长,诱导处理40d后,烟草的株高、叶宽和茎围与清水对照相比明显增加,其中株高增长72.43%,叶宽和茎围分别增加61.06%和29.05%。因此,试验结果说明毁灭炭疽菌诱抗蛋白具有诱导烟草产生抗病性和促进烟草生长的作用。