从热带假丝酵母中提取核酸的研究

采用正交设计试验等方法,研究了从热带假丝酵母(Candidatropicalis)中提取RNA的适宜条件为NaOH浓度1.5%,SDS浓度2%,NaCl浓度4%,抽提温度90℃,抽提时间3h。RNA粗品收率86.2%,纯度89.5%,可满足核苷酸的生产要求。     

酵母破壁酶和蜗牛酶辅助TRIzol试剂法提取酿酒酵母总RNA

该研究以酵母破壁酶、蜗牛酶破碎酿酒酵母（Saccharomyces cerevisiae）细胞壁，再使用总核糖核酸（RNA）提取试剂（TRIzol）法提取酵母总RNA，通过对总RNA进行浓度与纯度的分析，比较酶处理对RNA提取的影响。结果表明，酵母破壁酶的最佳提取条件为加酶量37.5 μL，提取温度27 ℃，提取时间15 min。在此最佳提取条件下，提取RNA质量浓度为1 079.05 ng/μL，A260 nm/A280 nm为2.10，A260 nm/ A230 nm为2.15；蜗牛酶的最佳提取条件为加酶量30 mg/mL，提取温度37 ℃，提取时间30 min。在此最佳提取条件下，提取RNA质量浓度为1 673.39 ng/μL，A260 nm/A280 nm为1.99，A260 nm/A230 nm为1.81。结果显示，酵母破壁酶的提取效果优于蜗牛酶。     

氨解法在啤酒酵母中提取RNA的应用与研究

研究了用氨解法从啤酒酵母中提取 RNA 的工艺,并得出了最佳工艺条件: 酵母浓度 10%,氨浓度 1.0%,三氯乙酸的浓度为 2%,破壁 50min,提取 40min。     

酵母RNA超声辅助提取工艺研究

为提高酵母RNA提取效果,采用超声辅助提取工艺,在单因素实验的基础上,采用超声处理时间、超声功率和提取时间进行三因素三水平响应面分析实验以优化此工艺条件.结果表明,酵母RNA超声辅助提取的最佳工艺条件为超声处理时间10min,超声功率300W,提取时间20min,在此工艺条件下,酵母RNA实际得率为9.56%,与模型预测值之间具有较好的拟合性.在3个因素中,超声处理时间、超声功率对酵母RNA得率的影响极显著,提取时间影响不显著,且相互之间无交互效应.     

废糖蜜培养高核酸酵母提取RNA的研究

利用糖蜜做碳源连续发酵培养高核酸酵母来提取RNA,以期综合利用制糖业的废物糖蜜。结果表明:利用糖蜜和葡萄糖母液做碳源培养酵母,前者酵母对糖的转化率达43.8%,后者转化率最高只有29.7%,且前者的菌体量和RNA量均高于后者;安装空气分布器的发酵罐酵母对糖的转化率为47.5%,没有空气分布器的转化率只有20.2%在稀释率不断提高的条件下,发酵液中RNA的含量不断提高,稀释率为0.75时,发酵液中RNA含量最高达13.8%,干菌浓度达19g/L;利用浓盐法提取酵母中的RNA得率达80.4%,纯度达92.3%。     

啤酒废酵母核苷类调味剂最佳工艺条件研究

采用超声波结合弱碱盐法提取啤酒废酵母RNA,以不同酵母浓度、NaCl浓度、超声功率和提取时间对啤酒酵母中核糖核酸RNA的提取进行单因素和正交试验.该方法提取核糖核酸RNA优化后最佳工艺为:酵母浓度5％,NaCl浓度6％,超声波功率200 W,提取时间30 min,用该工艺可使核糖核酸RNA的收率达到8.5％.提取的核糖核酸RNA可用于生产高质量的核苷类调味剂,应用潜力较大.     

盐法提取啤酒废酵母RNA的研究

采用正交设计试验法对盐法提取啤酒废酵母RNA工艺过程中的酵母浓度、NaCl浓度、抽提温度和抽提时间等因素进行了研究。用方差分析处理，实验结果表明：酵母浓度8％，NaCl 6％，抽提温度95℃，抽提时间6h是提取啤酒废酵母RNA的适宜条件，并将其用于啤酒厂废酵母泥的RNA提取试验，得率为3．23％。     

不同方法提取酿酒酵母总RNA的比较

选择试剂盒法、总核糖核酸（RNA）提取试剂（Trizol）法、热酚法3种方法提取酿酒酵母（Saccharomyces cerevisiae）总RNA,根据提取效果,选用酵母破壁酶辅助破壁并进行不同菌体量优化,通过对总RNA进行浓度和纯度的分析,比较不同方法对酿酒酵母总RNA提取的影响。结果表明,试剂盒法和Trizol法不适合提取酿酒酵母总RNA,但通过添加酵母破壁酶,可以提高提取效果。热酚法适合提取酿酒酵母总RNA,但添加酵母破壁酶反而会导致RNA降解。因此,使用热酚法提取酿酒酵母总RNA是较为有效且简便的方法。     

氨解法提取啤酒酵母中RNA的研究

以啤酒酵母为原料，通过氨解法进行RNA提取的研究。对影响RNA提取率的因素，如氨质量浓度的选择、破壁温度、破壁时间及酵母质量浓度进行了实验，获得最大提取率的条件为：氨质量浓度1％，破壁温度60℃，破壁时间60min，酵母质量浓度10％。通过正交试验表明酵母质量浓度为反应过程的最显著因素；45g湿酵母可提取0．55gRNA，再对RNA粗品进行精制，可得到白色固体粉末。     

影响氨解法RNA提取率因素的探讨与研究

啤酒废酵母是啤酒生产的重要副产物,其营养成分十分丰富,具有很高的利用价值,其中核酸(DNA和RNA)含量尤其是RNA的含量较高.据报道,从啤酒废酵母提取RNA的方法有浓盐法、混合盐法、表面活性剂法、稀碱法等,常用的有浓盐法和稀碱法两种.采用氨解法,通过正交实验和响应面法,探讨和研究了影响氨解法RNA提取率的主要因素,确定氨解法从啤酒废酵母中提取RNA的最佳工艺条件:酵母浓度10.0%,氨水浓度为1.0%,破壁温度60℃,破壁时间55min.     

Short communication: Eicosatrienoic acid and docosatrienoic acid do not promote vaccenic acid accumulation in mixed ruminal cultures

Previous research found that docosahexaenoic acid (C22:6n-3) was a component of fish oil that promotes trans-C18:1 accumulation in ruminal cultures when incubated with linoleic acid. The objective of this study was to determine if eicosatrienoic acid (C20:3n-3) and docosatrienoic acid (C22:3n-3), n-3 fatty acids in fish oil, promote accumulation of trans-C18:1, vaccenic acid (VA) in particular, using cultures of mixed ruminal microorganisms. Treatments consisted of control, control plus 5 mg of C20:3n-3 (ETA), control plus 5 mg of C22:3n-3 (DTA), control plus 15 mg of linoleic acid (LA), control plus 5 mg of C20:3n-3 and 15 mg of linoleic acid (ETALA), and control plus 5 mg of C22:3n-3 and 15 mg of linoleic acid (DTALA). Treatments were incubated in triplicate in 125-mL flasks, and 5 mL of culture contents was taken at 0 and 24 h for fatty acid analysis by gas-liquid chromatography. After 24 h of incubation, the concentrations of trans-C18:1 (0.87, 0.88, and 0.99 mg/culture), and VA (0.52, 0.56, and 0.62 mg/culture) were similar for the control, ETA, and DTA cultures, respectively. The concentrations of trans-C18:1 (5.51, 5.41, and 5.36 mg/culture), and VA (4.78, 4.62, and 4.59 mg/culture) were also similar between LA, ETALA, and DTALA cultures, respectively. These data suggest that C20:3n-3 and C22:3n-3 are not the active components in fish oil that promote VA accumulation when incubated with linoleic acid.     

Determination of ethanol,volatile fatty acids,lactic and succinic acids in fermentation liquids by gas chromatography

A rapid and simple quantitative method was developed to determine, by gas chromatography, the concentrations in fermentation liquids of ethanol, the C₂-C₆ volatile fatty acids, and lactic and succinic acids. Aqueous samples were acidified with 250μlml^?1 metaphosphoric acid (5:1 ratio), centrifuged, and injected directly on to a column containing a porous aromatic polymer (Chromosorb 101) maintained at 200°C in a gas chromatograph fitted with a flame ionisation detector. It was unnecessary to purify samples further before injection, although distillation and ion-exchange methods were examined. Derivatisation of lactic and succinic acids before injection was not necessary, but the lowest level of detection of these two relatively non-volatile acids was about four times greater than that for the volatile fatty acids. The method described was suitable for the analysis of rumen fluid, methane digester fluid, silage extracts and other anaerobic fermentation fluids. The relative retention times are given for 23 organic acids and six other fermentation end-products.     

Effects of abomasal infusions of fatty acids and 1-carbon donors on apparent fatty acid digestibility and incorporation into milk fat in cows

Our primary objective was to determine the effects of the abomasal infusion of 16-carbon (16C) and 22-carbon (22C) fatty acids (FA) on apparent FA digestibility, plasma FA concentrations, and their incorporation into milk fat in cows. Our secondary objective was to study the effects of 1-carbon donors choline and l-serine on these variables. Five rumen-cannulated Holstein cows (214 ± 4.9 d in milk; 3.2 ± 1.1 parity) were enrolled in a 5 × 5 Latin square experiment with experimental periods lasting 6 d. Abomasal infusates consisted of (1) palmitic acid (PA; 98% 16:0 of total fat), (2) PA + choline chloride (PA+CC; 50 g/d of choline chloride), (3) PA + l-serine (PA+S; 170 g/d of l-serine), (4) behenic acid (BA; 92% 22:0 of total fat), and (5) docosahexaenoic acid algal oil (DHA; 47.5% DHA of total fat). Emulsions were formulated to provide 301 g/d of total FA and were balanced to provide a minimum of 40 and 19 g/d of 16:0 and glycerol, respectively, to match the content found in the infused algal oil. Apparent digestibility of FA was highest in DHA, intermediate in PA, and lowest in BA. Digestibility of 16C FA was lowest in BA and highest in PA. The digestibility of 22C FA was highest in DHA relative to BA (99 vs. 58%), whereas 1-carbon donors had no effect on 22C FA digestibility. Plasma 16C FA concentrations were greatest with PA treatment, and 22C FA concentrations were ~3-fold greater in DHA-treated cows relative to all other treatments. Milk fat 16:0 content was highest in PA relative to BA and DHA (e.g., 37 vs. 27% in PA and DHA), whereas the milk yield of 16:0 was higher in PA relative to DHA (i.e., 454 vs. 235 g/d). Similarly, milk 22:0 content and yield were ~10-fold higher in BA relative to all other treatments, whereas DHA treatment resulted in higher content and yield of 22:6 in milk fat relative to all other treatments (41- and 38-fold higher, respectively). Consequently, the content of FA >16C (i.e., preformed) was higher in milk fat from cows infused with BA and DHA relative to PA. De novo FA content in milk did not differ between PA, PA+CC, and PA+S (~16% of milk fat) but was higher in BA and DHA treatments (19 and 21%, respectively). We conclude that FA carbon chain length and degree of saturation affected FA digestibility and availability for absorption as well as their incorporation into milk fat. The abomasal infusion of choline chloride and l-serine did not modify these variables relative to infusing palmitic acid alone.     

奶粉脂肪酸与乳制品风味关系研究

用气质（GC—MS）联用色谱分析了11个商业奶粉样品的脂肪酸组成以及含量，每个样品均检测到了28种脂肪酸，在表现奶粉风味的4个呈味脂肪酸，也即辛酸、己酸、壬酸和葵酸中只检测到了辛酸和葵酸。辛酸和葵酸含量在进口奶粉中普遍高于国产奶粉。国产奶粉中辛酸和葵酸的含量以2号最好，3号其次。亚油酸含量在国产奶粉中普遍高于进口奶粉。     

气相色谱法同时快速测定食品中丙酸、山梨酸、苯甲酸及脱氢乙酸

通过液液萃取净化样品研究,建立了食品中丙酸、山梨酸、苯甲酸、脱氢乙酸及其盐含量气相色谱同时快速测定方法,适用于固体非酯(脂)类食品的检测。结果表明:丙酸的回收率在85.1%~91.3%之间,其余3种防腐剂的回收率均在95.2%~99.4%之间;实验室内变异系数(CV,n=6)最大值≤4.7%,4种防腐剂检出限均在0.002 g/kg以下。4种目标物在有杂质干扰时,可用不同的极性毛细管柱做进一步的确认。本方法具有适用范围广、检测效率高、重现性好、准确度高、检出限低的特点,推广应用对我国食品安全的监督检验具有重要的意义。     

酸味酿造产品中三酸比例评析

酸味酿造产品中乳酸、醋酸、丁酸共存,但比例不同形成的酸味特征也不同。控制不同的环境条件,创造出不同的微生物区系,形成不同的三酸比例,才能形成不同的产品风格。该文对常见的酸味酿造产品中微生物区系的变化及三酸含量进行了分析。     

花生四烯酸、二十二碳六烯酸和二十碳五烯酸 在炎症中的作用概述

心脑血管疾病、肿瘤、糖尿病、神经系统疾病、自身免疫等疾病严重危害着人类的生命和健康,并消耗着大量医疗资源。事实上,很多疾病发生和发展的背后都伴随着炎症反应,炎症是众多疾病的病理基础,甚至是导致这些疾病的诱因。炎症本身是机体的防御性反应,但过度的炎症反应和长期慢性炎症会损害机体的稳态。炎症的调节和控制由炎症介质介导,花生四烯酸(arachidonic acid,AA)、二十二碳六烯酸(docosahexaenoic acid,DHA)和二十碳五烯酸(eicosapentaenoic acid,EPA)等长链多不饱和脂肪酸(10ng-chain polyunsaturated fatty acids,LC-PUFAs)的衍生物是一类重要的调控炎症的介质。炎性细胞间的交流和细胞内信号传递与LC-PUFAs有关。AA经环氧酶和脂氧合酶合成的类二十烷酸主要起促炎作用,但有的也有抗炎作用。DHA和EPA在体内起抗炎作用,由它们合成的消退素(resolvins,Rvs)和保护素(protectin,PD)是重要的抗炎活性物质。DHA和EPA还可以干扰炎性细胞内信号传导途径来抑制炎症反应。本文从炎症与疾病的关系、LC-PUFAs的衍生物及其促炎和抗炎机制等方面综述了AA、DHA和EPA在炎症中的作用。     

Growth of Aeromonas hydrophila K144 as Affected by Organic Acids

The influence of different acids on the aerobic growth kinetics of Aeromonas hydrophila was studied in BHI broth with 0.5 and 2.0% NaCl incubated at 5 and 19°C. Growth curve data were analyzed by the Gompertz equation and a nonlinear regression program; generation and lag times were calculated from the Gompertz parameters. Type of acid, pH, NaCl level and temperature influenced lag and generation times. The organic acids (acetic, lactic, citric and tartaric) inhibited growth at higher pH values than inorganic acids (HCl and H₂SO₄). The high NaCl level interacted with type of acid and pH to restrict growth of the organism at the lower temperature of incubation. Acetic and lactic acids were effective in controlling the growth of A. hydrophila and could readily be combined with low holding temperature to render foods free of the organism.     

杂多酸催化合成辛酸蔗糖酯

以蔗糖、辛酸为原料,杂多酸为催化剂合成辛酸蔗糖酯。用L16(45)正交设计优化实验,高效液相色谱法分析反应液组成。考察了催化剂种类和用量、反应温度、原料配比、反应时间等因素对辛酸蔗糖酯产率的影响,发现以二甲基亚砜为溶剂、蔗糖与辛酸摩尔比1∶9、磷钨酸用量为蔗糖质量的2.0%、110℃反应时间6h,蔗糖转化率达60%,产物产要是二酯。动力学研究发现,蔗糖反应级数为一级,反应表观速率常数为0.0059min-1(90℃)、0.0117min-1(110℃),反应表观活化能Ea=39.57kJ/mol。     

气相色谱法同时测定保健食品中的5种 不饱和脂肪酸

目的建立气相色谱法同时测定保健食品中亚油酸、α-亚麻酸、二十碳五烯酸(eicosapentaenoic acid,EPA)、二十二碳六烯酸(docosahexaenoic acid,DHA)和二十二碳五烯酸(docosapentaenoic acid,DPA)的含量。方法样品先采用氢氧化钾甲醇溶液进行皂化处理,再用三氟化硼甲醇溶液甲酯化,经HP-FFAP色谱柱(30m×0.53 mm,1.0μm)分离测定。结果 EPA甲酯、DHA甲酯、DPA甲酯、亚油酸甲酯、α-亚麻酸甲酯分别在0.03927~1.178、0.04200~1.260、0.03449~1.035、0.08368~1.255、0.08482~4.241 mg/mL的浓度范围内线性关系良好,相关系数r均大于0.999;检出限分别为0.0039、0.0042、0.0034、0.0042、0.0042 mg/mL;加标回收率在91.1%~109.3%之间,相对标准偏差均小于5%。结论该方法操作简单快捷,适用于保健食品中亚油酸、α-亚麻酸、EPA、DPA和DHA的测定。