前体氨基酸对热带假丝酵母产谷胱甘肽的影响

以能利用木糖发酵产谷胱甘肽(GSH)的热带假丝酵母突变株CV26为实验菌株,分别研究了添加L-半胱氨酸、谷氨酸、甘氨酸3种前体氨基酸对CV26产GSH的影响。在单因素实验基础上,对3种前体氨基酸的添加进行了正交实验,结果表明:在GSH发酵的12h添加6mmol/L的甘氨酸和2mmol/L的谷氨酸,24h添加3mmol/L的L-半胱氨酸,GSH的产量和胞内含量都有较大的提高,分别达到149.28mg/L和20.43mg/g,比对照组分别提高了51.5%和57.8%。     

Influence of dietary linoleic acid on egg fatty acid composition in hens deficient in essential fatty acids

The effect on egg yolk lipids of adding linoleic acid in the form of corn oil to the diet of hens depleted of essential fatty acids over a prolonged period was examined. There was an immediate increase in the amount of linoleate deposited in all yolk lipid fractions. The addition of 8% corn oil resulted in a maximum value of about 20% lineoleic acid in the egg yolk fatty acids being attained over a period of 14 days. This increase in lineoleate deposition was accompanied by a reduction in the level of oleic acid. Minor adjustments in the other egg fatty acids accompanied these major changes.     

Organic acids and sugars composition of harvested pomegranate fruits

For two consecutive seasons, 40 Spanish pomegranate cultivars (cvs) were analysed and their individual organic acids and sugars compositions were examined. Intervarietal differences in acidity content reported by different authors were confirmed. According to organoleptic characteristics and chemical compositions three groups of varieties were established: sweet (SWV), soursweet (SSWV) and sour (SV). On average, for two seasons, total organic acids on a dry basis ranged between 0.317 g/100 g (SWV) and 2.725 g/100 g (SV). Citric, malic, oxalic, acetic (first reported here), fumaric, tartaric and lactic acids were detected, although lactic and fumaric were not quantifiable. On average, for both seasons, citric acid was predominant with a range of 0.142–2.317 g/100 g (average content for all CVS, 0.282 g/100 g). Malic acid was the second most abundant, with a range of 0.135–0.176 g/100 g (average of 0.139 g/100 g). Total sugars ranged between 11.43 g/100 g and 13.5 g/100 g. Glucose, fructose, sucrose and maltose were detected, although maltose (first reported here) was not quantifiable. Fructose ranged between 5.96 g/100 g and 7.04 g/100 g, with an average of 6.58 g/100 g, quite similar to that of glucose (6.14 g/100 g). Sour cv showed the lowest fructose and glucose contents. The average sucrose content was 0.01 g/100 g. Other differences among the groups of cvs were detected. Low total sugars and high acids were found in SV. The SSWV group had higher sugars than the SV. However, no difference in total sugars between SSWV and SWV was found. A lower acids content than SV but higher than SWV was found in the SSWV group. No other studies have been published so far on the individual organic acids and sugars of pomegranate fruit. Received: 27 July 1999 / Revised version: 28 September 1999     

生长因子和乳化剂对热带假丝酵母产十二碳二元酸发酵的影响

通过液体摇瓶分批发酵,研究生长因子和乳化剂对热带假丝酵母(Candida tropicalis)利用正十二烷发酵产十二碳二元酸的影响,生长因子为多种氨基酸和维生素,乳化剂为吐温60和吐温80.研究结果表明,对产酸的促进作用依次为维生素B2,丝氨酸,维生素B1和脯氨酸.添加60μg/L维生素B2可维持较高产酸水平,添加1.0g/L丝氨酸比不添加丝氨酸的产酸量约提高30%.与不添加乳化剂相比,添加吐温的菌体产酸量明显提高,添加10g/L吐温60和吐温80的最大产酸量分别提高51.84%和48.14%.添加吐温60还能发酵缩短周期,添加20g/L吐温60的菌体产酸量最高可达81.63g/L.     

巧克力中脂肪酸组成及反式脂肪酸含量的分析

目的建立测定巧克力中脂肪酸组成和反式脂肪酸含量的气相色谱方法。方法采用氢氧化钾-甲醇甲酯化方法,将甘油三酯转化为脂肪酸甲酯,并使用气相色谱-氢火焰离子化检测器进行分析。结果以三油酸甘油三酯为模型化合物,确定甲酯化效率为99.8%。使用面积归一化定量方法,对市面上不同品牌、不同种类的5种巧克力进行分析。巧克力油脂中主要脂肪酸为棕榈酸、硬脂酸和油酸,含量范围分别为:25%~27%、32%~35%及30%~32%;反式脂肪酸含量范围为0.4%~1.1%(以油脂中含量计)。结论该方法简单快速,适合巧克力油脂中脂肪酸组成和反式脂肪酸含量的分析。     

Chemical composition of silages treated with some volatile fatty acids,with special reference to the changes in sugars

In eight separate experiments with laboratory silos, silages were prepared with 50 mmol caproic (nC₆), isocaproic (iC₆), valeric (nC₅) and isovaleric (iC₅) acid additions per kg Italian ryegrass or cocksfoot, and stored at 25°C for 70 days. In the nC₆ and iC⁶ treatments, fermentation was consistently inhibited, and also the contents of water-soluble carbohydrates (WSC) were considerably higher in the silages than in the grasses. This increase in WSC was partly explained by the increase in glucose but the difference between WSC and “glucose + fructose” was clearly larger in the silages than in the grasses. In the nC₅ and iC⁵ treatments, various results were obtained; in some cases, presumably due to high dry matter content, fermentation was inhibited and WSC increased, while, in one case, fermentation was improved with higher lactic acid and lower butyric acid production than in the control silage. According to the results of five experiments with bag silos, although the inhibition of fermentation was observed by the treatment with nC₆, little or no increase in WSC during ensilage was found.     

冷适应对一株植物乳杆菌膜脂肪酸组成和膜蛋白表达的影响

从15株乳杆菌中筛选出一株冷敏感性较高的菌株(植物乳杆菌KLDS1.0703),研究冷适应对该株菌细胞膜脂肪酸组成和膜蛋白表达的影响。根据生长速率与温度(开氏温度)相关性的Arrhenius曲线及冷适应时间对存活率的影响,确定该菌株的冷适应条件为:培养至对数中期,10℃冷适应处理4 h。应用GC/MS分析冷适应前后菌体的膜脂肪酸组成发现,脂肪酸18:1△9c的结构中不饱和键由反式转变为顺式;应用双向电泳分析冷适应前后菌体的膜蛋白质组成,分析找到23个差异表达的蛋白点,其中3个为特异表达蛋白质点。结果表明,冷适应处理诱导植物乳杆菌KLDS1.0703膜脂肪酸结构向熔点降低方向转变,而且膜蛋白质出现特异性表达。     

辐照处理对薏仁米中脂肪酸的影响

目的 研究了辐照剂量、温度和湿度等不同条件对薏仁米中储藏过程脂肪酸变化的影响。方法 采用气相色谱(GC)对脂肪酸样品进行检测,采用面积归一化法进行定量分析。色谱柱为CP-SIL 88毛细管柱(100m×0.25μm×0.2mm),进样量为1μl,分流比为1：10,以氦(99.999%),流速为6.3mLmin-1。结果 薏仁米中共检测出13种脂肪酸成分,其中6种不饱和脂肪酸,5种饱和脂肪酸,2种反式脂肪酸,其中C16;0、C18:1-9C、C18:2-9C,12C为薏仁米中主要脂肪酸,达到脂肪酸总含量的90以上。结论 辐照处理、高湿度、高温都会加速薏仁米中不饱和脂肪酸的氧化,导致不饱和脂肪酸含量降低,产生有害的反式脂肪酸,不利于薏仁米的储藏。     

热带假丝酵母发酵生产木糖醇的研究

对热带假丝酵母 (C tropicalis )As2 1 776发酵木糖醇的营养条件进行了初步研究。初始木糖浓度在 80g/L附近时木糖醇转化率较高 ,限制性供氧条件下有利于木糖醇积累。酵母膏和蛋白胨是比较适合产木糖醇的有机氮源 ,而酵母膏更利于酵母细胞生长。培养基中添加 2 g/L的(NH4 ) 2 HPO4 、2～ 6g/L的NaCl、1～ 3g/L的KH2 PO4 、0 1～ 0 3 g/L的MgSO4 ·7H2 O能提高木糖醇的转化率     

热带假丝酵母两态型的控制研究

通过对热带假丝酵母在不同培养基上的培养,研究了培养温度、pH值、脯氨酸浓度及培养时间对酵母两种形态的影响。通过正交试验得出:最有利于菌丝型生长的条件是:YX培养基、42℃、pH值6.5、接种量5%、木糖含量2%、24h补加10mmol/L脯氨酸、215r/min摇床培养,验证试验表明其最大丝化率为73.39%,平均丝化率为67.29%;最有利于酵母型生长的条件是:YM培养基、pH值4.5、27℃、215r/min摇床培养,其最大丝化率仅为1.14%,平均丝化率为0.08%。     

Incorporation of selected long-chain fatty acids into trilinolein and trilinolenin

The effect of chain length, number of double bonds, the location and geometry of double bonds, the reaction conditions, and reactivity of different lipases on the incorporation of selected long-chain fatty acids (LCFA) into triacylglcerols, such as trilinolein (tri C18:2) and trilinolenin (tri C18:3) is examined. This study also discusses reasons behind different degrees of incorporation of selected LCFA into tri C18:2 or tri C18:3 on a molecular basis. Five lipases, namely Candida antarctica (Novozyme-435), Mucor miehei (Lipozyme-1M), Pseudomonas sp. (PS-30), Aspergillus niger (AP-12), and Candida rugosa (AY-30) were screened for their effect on catalyzing the acidolysis of trilinolein (tri C18:2) or trilinolenin (tri C18:3) with selected C18, C20 and C22 fatty acids (FA). Incorporation of a mixture of C18 FA into trilinolein, using Pseudomonas sp., the most effective lipase, was in the order of SA > OA > GLA > ALA > CLA. Meanwhile, the degree of n-6 FA incorporation into tri C18:2 with Pseudomonas sp. was in the order of GLA > AA > CLA. The order of incorporation of n-3 FA into trilinolein using lipases from C. antarctica and M. miehei was ALA > EPA > DPA > DHA.     

Cooking effects on fat and fatty acids composition of chicken muscles

Total lipids content of chicken breast and thigh muscles were investigated. Effects of boiling and roasting cooking treatments on these muscles were also studied to evaluate the probable changes in their fat contents, values of acid, peroxide and thiobarbituric acid (as measures for lipolysis and oxidative deterioration of fat) as well as to estimate their fatty acids (saturated and unsaturated) composition. The obtained results were tabulated and discussed.     

蓖麻油的理化性质及脂肪酸组成分析

对一级蓖麻油的理化性质进行了测定,并利用气相色谱-质谱联用仪（GC—MS）对蓖麻油的脂肪酸组成进行了分析和鉴定。     

葡萄糖-6-磷酸脱氢酶基因的Candida tropicalis过量表达及其对木糖醇合成代谢的影响

研究葡萄糖-6-磷酸脱氢酶基因g6pd过量表达对Candida tropicalis木糖醇生物合成代谢的影响。克隆Candidatropicalis CT16的g6pd基因,并将其与表达载体pYES-pgk重组连接,构建重组载体pYES-pgk-g6pd,LiAc/ssDNA/PEG方法转化导入C. tropicalis CT16,筛选阳性转化子,实现g6pd基因的过量表达。结果表明：发酵62 h,阳性转化子C. tropicalis SYG5的葡萄糖-6-磷酸脱氢酶活力提高了300%,发酵液中木糖醇质量浓度达到79.90 g/L,较野生型对照菌株的木糖醇产量提高了12.41%,木糖醇产率提高了44.94%。因此,葡萄糖-6-磷酸脱氢酶在C. tropicalis木糖醇的合成代谢途径中发挥重要作用,增强g6pd基因的表达,可以明显提高菌体NADPH供应量和还原力,有利于木糖醇的生物合成。     

氮元素对地木耳脂肪酸的影响

采用改进的Bligh-Dyer（mBD）法,气相色谱-质谱联用法（GC-MS）对含氮（BG11）和无氮（BG110）条件下培养的地木耳（Nostoc commune）脂肪酸进行提取、分离和测定。结果显示:两种培养条件下的地木耳脂肪酸都以C16和C18脂肪酸为主,而且不饱和脂肪酸含量均高于50%。无氮培养条件下地木耳总脂肪酸含量为13.29mg/g,饱和脂肪酸占36.91%,不饱和脂肪酸占63.09%,其中C18∶1的含量为15.99%;含氮条件下培养的地木耳总脂肪酸含量为7.72mg/g,饱和脂肪酸占47.91%,不饱和脂肪酸占52.09%,其中C18∶1的含量为1.74%。结论:无氮培养地木耳的脂肪酸含量显著高于含氮培养组（p<0.05）,表明氮源缺失有利于地木耳脂肪酸特别是不饱和脂肪酸的积累。      

氮元素对地木耳脂肪酸的影响

采用改进的Bligh-Dyer(mBD)法,气相色谱-质谱联用法(GC-MS)对含氮(BG11)和无氮(BG110)条件下培养的地木耳(Nostoc commune)脂肪酸进行提取、分离和测定.结果显示:两种培养条件下的地木耳脂肪酸都以C16和C18脂肪酸为主,而且不饱和脂肪酸含量均高于50％.无氮培养条件下地木耳总脂肪酸含量为13.29mg/g,饱和脂肪酸占36.91％,不饱和脂肪酸占63.09％,其中C18∶1的含量为15.99％;含氮条件下培养的地木耳总脂肪酸含量为7.72mg/g,饱和脂肪酸占47.91％,不饱和脂肪酸占52.09％,其中C18∶1的含量为1.74％.结论:无氮培养地木耳的脂肪酸含量显著高于含氮培养组(P＜0.05),表明氮源缺失有利于地木耳脂肪酸特别是不饱和脂肪酸的积累.     

Lipomobilization in periparturient dairy cows influences the composition of plasma nonesterified fatty acids and leukocyte phospholipid fatty acids

The periparturient period is characterized by sudden changes in metabolic and immune cell functions that predispose dairy cows to increased incidence of disease. Metabolic changes include alterations in the energy balance that lead to increased lipomobilization with consequent elevation of plasma nonesterified fatty acids (NEFA) concentrations. The objective of this study was to establish the influence of lipomobilization on fatty acid profiles within plasma lipid fractions and leukocyte phospholipid composition. Blood samples from 10 dairy cows were collected at 14 and 7 d before due date, at calving, and at 7, 14, and 30 d after calving. Total lipids and lipid fractions were extracted from plasma and peripheral blood mononuclear cells. The degree of lipomobilization was characterized by measurement of plasma NEFA concentrations. The fatty acid profile of plasma NEFA, plasma phospholipids, and leukocyte phospholipids differed from the composition of total lipids in plasma, where linoleic acid was the most common fatty acid. Around parturition and during early lactation, the proportion of palmitic acid significantly increased in the plasma NEFA and phospholipid fractions with a concomitant increase in the phospholipid fatty acid profile of leukocytes. In contrast, the phospholipid fraction of long-chain polyunsaturated fatty acids in leukocytes was diminished during the periparturient period, especially during the first 2 wk following parturition. This study showed that the composition of total plasma lipids does not necessarily reflect the NEFA and phospholipid fractions in periparturient dairy cows. These findings are significant because it is the plasma phospholipid fraction that contributes to fatty acid composition of membrane phospholipids. Increased availability of certain saturated fatty acids in the NEFA phospholipid fractions may contribute to altered leukocyte functions during the periparturient period.