产业动向

<正>安琪酵母抽提物产能跃居全球第一安琪是酵母抽提物的"国家九五科技攻关项目"承担者,经过近二十年的发展,该企业在各个方面均已遥遥领先。目前公司拥有4.6万吨酵母抽提物产能,其规模已跃居全球第一安琪品牌已不仅仅代表酵母及酵母抽提物,更是优质食品原料的代名词。在鲜味剂市场,酵母抽提物凭借"增鲜增味、食品属性、降盐淡盐、耐受性强"等突出优势,近年来在食品行业发展     

酵母自溶抽提物的研究

以活性干酵母和耐高温酒精酵母为对象,研究自溶抽提过程,并对自溶条件进行了优化。比较了两种酵母主要抽提物蛋白质、核酸的含量和抽提率,及氨基酸的组成,并用电泳法初步探讨了添加中性蛋白酶对酵母自溶的影响机理     

酵母抽提物对CHO细胞生长及抗体表达的影响

为了深入认识酵母抽提物在中国仓鼠卵巢(CHO)细胞生长及单克隆抗体表达过程中所发挥的作用,综合考察了传代培养和批式培养过程中,不同浓度酵母抽提物条件下CHO细胞生长、抗体表达以及营养物代谢的情况。传代培养过程中,低浓度(1 g/L)的酵母抽提物能够显著促进CHO细胞的生长,高浓度(5-10 g/L)的酵母抽提物则会显著抑制CHO细胞的生长;同时,传代过程中添加酵母抽提物不会影响种子细胞在批式培养中的表现。批式培养过程中,抗体比生成速率随酵母抽提物浓度的提高而升高,浓度为10 g/L时获得最高抗体产量。通过采用细胞生长阶段低浓度、产物表达阶段高浓度的添加策略,酵母抽提物在动物细胞培养过程中可发挥巨大的应用价值。     

过量无机盐及谷氨酸抑制重组菌核黄素发酵

在重组枯草芽孢杆菌24/pMX45核黄素发酵中,酵母粉促进核黄素合成,酵母抽提物抑制核黄素合成。分析显示,酵母抽提物的无机离子和游离氨基酸含量均高于酵母粉。在酵母粉基础发酵培养基中,添加各种无机离子和游离氨基酸,使其含量与酵母抽提物相同。摇瓶发酵结果表明:过量的无机离子和谷氨酸对核黄素合成有显著的抑制作用。酵母抽提物含有较高浓度的谷氨酸,是其抑制核黄素合成的主要原因。     

含高RNA酵母的分离,鉴定和应用

从蔗糖糖蜜及工业废水中分离到的一株高蛋白质,高ＲＮＡ酵母,菌体ＲＮＡ含量平均达１８．３,蛋白质含量达５０％以上,经鉴定为热带假丝酵母,用ＧＭ５０生产酵母抽提物,自溶后抽提物平均得率达７０％以上,抽提物蛋白含量达６０％以上,游离氨基酸占部氨基酸５０％,菌体蛋白利用率高达７８％。     

脱核酸酵母的A·S1398酶解及酵母蛋白的提取与分析

<正> 在核酸工业中,大量脱去核酸的酵母残渣含有50％左右的蛋白质,这种丰富的天然蛋白源至今尚未被利用,许多部门廉价出售以做饲料甚至当废料处理。考虑到酵母蛋白的营养价值较高、原料来源比较丰富等因素,本文就脱核酸酵母的进一步利用进行了初步探讨。     

一种从酵母细胞中提取组蛋白的方法

为了制备体外酵母DNA序列组装核小体所需的组蛋白,利用酸抽提方法从未经饥饿处理和经过不同时间饥饿处理的酿酒酵母细胞中分离组蛋白,经SDS-PAGE电泳分析和Bradford法测定蛋白浓度,发现抽提物中含有组蛋白H1、H2A、H2B、H3和H4,电泳条带位置正确、纯度较高,正常细胞的抽提物中蛋白总量达到158 μg/mL.试验结果表明该方法可以提取出较高质量的酿酒酵母组蛋白.     

脱色希瓦氏菌S12的铁还原性能研究*

从印染废水中分离得到了一株具有染料脱色功能的希瓦氏菌脱色新种。该菌能在厌氧条件下利用Fe3+作为末端电子受体获得能量,支持细胞生长。在pH8．0,温度30℃,柠檬酸铁800mg／L,乳酸钠2g／L,酵母抽提物0．5g／L的条件下,培养8h的过程中,菌体细胞量的增长完全与Fe3+的还原发展趋向一致。同时考察了碳氮源、乳酸钠、酵母抽提物、pH值和温度等方面对该菌株的生长和铁还原特性的影响。结果表明,菌体生长以LB为最好,以葡萄糖和乳酸钠为碳源时对铁还原有利。在酵母抽提物浓度4g／L范围内,菌体生长量和铁还原率     

柠檬酸废水生产饲料酵母

无锡轻工业学院与清江食品总厂完成日处理15吨柠檬酸废液生产饲料酵母的工艺及设备运转,生产70多批就得商品酵母粉10多吨,并通过鉴定。发酵干酵母得率11.7克/升,酵母收回48.51％,酵母粗蛋白含量48％左右,水分1—率％,含18种氨基酸,安全无毒,每吨柠檬酸废     

珍奥酵母核酸对环磷酰胺致小鼠免疫功能低下的影响

目的 通过环磷酰胺致小鼠免疫功能低下,建立BALB/C小鼠免疫功能低下模型,评价珍奥酵母核酸对小鼠免疫功能低下的作用.方法 选用BALB/C小鼠,随机分组,分别给予相应的处理,选择T淋巴细胞亚群CD69+/CD3+比值、NK细胞亚群CD69+/NKG2D+比值、淋巴细胞转化率及血清IL-2含量作为细胞免疫的指标.结果 核酸各剂量组和添加剂组均可使免疫低下小鼠外周血和脾的T淋巴细胞亚群CD69+/CD3+比值、NK细胞亚群CD69+/NKG2D+比值提高,同时可提高免疫低下小鼠淋巴细胞转化率及IL-2水平,尤以高、中剂量核酸组和添加剂组明显(P＜0.05).结论 珍奥酵母核酸可以提高免疫低下小鼠的免疫功能,以其为珍奥酵母核酸的临床应用及提高机体免疫力提供了实验依据.     

Physiological and nutritional features of Corynebacterium pyogenes

Growth and acid metabolic products were similar when Corynebacterium pyogenes was grown aerobically or anaerobically in a serum-free medium (SFM). This indicated that C. pyogenes obtains energy for growth primarily by fermentative metabolism even under aerobic growth conditions. Growth yield was reduced by 90% in SFM minus glucose, 50% in SFM minus NaHCO3, 90% in SFM minus yeast extract, 100% in SFM minus Trypticase and yeast extract, and 30% in SFM minus haemin or Trypticase. Growth was not detectable when a known mixture of amino acids, vitamins, and nucleic acid bases were substituted for Trypticase and yeast extract in SFM; addition to the latter medium of a peptide source such as Trypticase or casitone supported good growth of the organism. When NaHCO3 was omitted from SFM and dissolved CO2 in the medium was rigorously excluded, growth was undetectable indicating that C. pyogenes has an obligate requirement for CO2 for growth. Succinate, formate and acetate were the major fermentation products in SFM, whereas in SFM minus HCO-3 or haemin, lactate was the major product and only small quantities of other acids accumulated.     

Some methods for processing of single-cell protein

Methods for the production of protein concentrates, with a low content of nucleic acid, in kilogram quantities from yeast have been studied with the aid of equipment designed for operation on pilot-plant scale. The influence of drum drying and mechanical disintegration on the nutritive value of the yeast was also investigated. Drum drying and mechanical disintegration improved the nutritive value of the yeast but high extractability of protein and nucleic acid was only obtained after mechanical disintegration. Protein concentrates without and with cell walls were produced from mechanically disintegrated yeast. The different fractions which were obtained when separating cell walls and precipitating protein by heating at alkaline pH, were analyzed. After protein precipitation, about 90% of the RNA could be precipitated from the supernatant by addition of acid, giving a product containing 50% RNA of the dry weight. The protein precipitate obtained after cell wall separation had an RNA content of less than 2% and contained 70–l75% of the amino acids in the starting yeast material. Protein concentrates containing cell walls were produced by precipitating protein by heating at alkaline pH directly after mechanical disintegration. The content of RNA was about 2% and the yield of amino acids was 70–80%. It was found that the nutritive value of the protein concentrate was higher than that of the starting yeast material. To produce such a protein concentrate on a large scale, the process described can probably be employed.     

Reduction of the nucleic acid content of single-cell protein concentrates

Methods for reducing the content of nucleic acid in protein concentrates from disintegrated yeast and microalgae were investigated. Protein concentrates were prepared by acid precipitation of extracted protein after cell wall separation. The influence of alkaline protein extraction on the content of RNA in isoelectrically precipitated protein concentrates was studied. It was found that when a strong decrease in the RNA content was obtained, this was followed by a decrease in the yield of protein concentrate. Protein concentrates were also prepared without cell wall separation by precipitation with different agents after cell disintegration. In the precipitates from microalgae, a RNA reduction was obtained. Precipitation of yeast, protein gave no essential reduction with the precipitants used. Precipitation of yeast protein by heating at an alkaline pH gave a protein concentrate with a low content of RNA. A slightly lower RNA content was obtained when the precipitation was performed in the presence of NaCl. The yield of amino acid nitrogen was 70–80% and the RNA content was 1–2%. A process with precipitation at alkaline pH for the production of microbial protein concentrates with a low content of nucleic acid is suggested.     

高糖和氮源对鼠李糖乳杆菌(Lactobacillus rhamnosus)L-乳酸发酵的影响

鼠李糖乳杆菌经实验室耐高糖高酸选育,能够在高糖浓度下高效高产L-乳酸。以酵母粉为氮源和生长因子,葡萄糖初始浓度分别为120 g/L和146 g/L,摇瓶培养120h,L-乳酸产量分别为104g/L和117.5g/L,L-乳酸得率分别为86.7%和80.5%。高葡萄糖浓度对菌的生长和乳酸发酵有一定的抑制。增加接种量,在高糖浓度发酵条件下,可以缩短发酵时间,但对增加乳酸产量效果不明显。乳酸浓度对鼠李糖乳杆菌生长和产酸有显著的影响。初始乳酸浓度到达70g/L以上时,鼠李糖乳杆菌基本不生长和产酸,葡萄糖消耗也被抑制。酵母粉是鼠李糖乳杆菌的优良氮源,使用其它被测试的氮源菌体生长和产酸都有一定程度的下降。用廉价的黄豆粉并补充微量维生素液,替代培养基中的酵母粉,可以使产酸浓度和碳源得率得以基本维持。     

Precipitation of nucleic acids with poly(ethyleneimine).

Removal of nucleic acids from cell extracts is a common early step in downstream processing for protein recovery. We report on the precipitation of nucleic acids from a homogenate of Saccharomyces cerevisiae by addition of the cationic polyelectrolyte poly(ethyleneimine) (PEI), focusing on the effect of PEI dosage on particle size, protein loss, and extent of nucleic acid removal in both batch and continuous mode. Better than 95% removal of nucleic acids from yeast homogenates was achieved by means of precipitation with PEI with protein losses of approximately 15% with or without previous removal of cell debris. The coprecipitated protein is predominately large molecular weight material and exhibits both low and high isoelectric points. Such treatment does not aggregate the cell debris; size distribution of the precipitated particles from a continuous precipitator is very similar to that for protein precipitation.     

Optimization of lactic acid production from beet molasses by Lactobacillus delbrueckii NCIMB 8130

Production of lactic acid from beet molasses by Lactobacillus delbrueckii NCIMB 8130 in static and shake flask fermentation was investigated. Shake flasks proved to be a better fermentation system for this purpose. Substitution of yeast extract with other low cost protein sources did not improve lactic acid production. The maximum lactic acid concentration was achieved without treatment of molasses. A Central Composite Design was employed to determine the maximum lactic acid concentration at optimum values for the process variables (sucrose, yeast extract, CaCO₃). A satisfactory fit of the model was realized. Lactic acid production was significantly affected both by sucrose–yeast extract and sucrose–CaCO₃ interactions, as well as by the negative quadratic effects of these variables. Sucrose and yeast extract had a linear effect on lactic acid production while the CaCO₃ had no significant linear effect. The maximum lactic acid concentration (88.0 g/l) was obtained at concentrations for sucrose, yeast extract and CaCO₃ of 89.93, 45.71 and 59.95 g/l, respectively.     

代谢工程改造野生耐酸酵母生产L-乳酸

以选育低pH条件下高产L-乳酸的酵母菌为目的,从自然样品中筛选分离得到一株能在pH 2.5 (乳酸调节) 的培养基中生长且不利用乳酸的酵母 (初步鉴定为木兰假丝酵母Candida magnolia);进一步将来源于米根霉As3.819的乳酸脱氢酶编码基因 (ldhA) 插入含有G418抗性基因的酵母穿梭载体,构建了重组质粒pYX212-kanMX-ldhA,电转化入野生型C. magnolia中,筛选获得了一株具有产L-乳酸能力的重组菌株C. magnolia-2;通过发酵实验表明,该重组菌产L-乳酸的最     

CRYSTALLINE RIBONUCLEASE

1. A crystalline enzyme capable of digesting yeast nucleic acid has been isolated from fresh beef pancreas. 2. The enzyme called "ribonuclease" is a soluble protein of albumin type. Its molecular weight is about 15,000. Its isoelectric point is in the region of pH 8.0. 3. Ribonuclease splits yeast nucleic acid into fragments small enough to diffuse readily through collodion or cellophane membranes. 4. The split products of digestion, unlike the undigested yeast nucleic acid, are not precipitable with glacial acetic acid or dilute hydrochloric acid. 5. The digestion of yeast nucleic acid is accompanied by a gradual formation of free acid groups without any significant liberation of free phosphoric acid. 6. Ribonuclease is stable over a wide range of pH even when heated for a short time at 100°C. Its maximum stability is in the range of pH 2.0 to 4.5. 7. Denaturation of the protein of ribonuclease by heat or alkali, or digestion of the protein by pepsin, causes a corresponding percentage loss in the enzymatic activity of the material.     

Growth behaviour and indole acetic acid (IAA) production by a Rhizobium isolated from root nodules of Alysicarpus vaginalis DC

From the root nodules of Alysicarpus vaginalis DC, the symbiont was isolated and identified as a Rhizobium sp. The bacteria produced a high amount (107 microg/ml) of indole acetic acid (IAA) in culture from tryptophan supplemented yeast extract mannitol medium. The isolate preferred L-isomer of tryptophan for maximum IAA production. The production was maximum when the bacteria reached its stationary phase of growth. The production of IAA could be increased up to 70% over yeast extract glucose medium by supplementing ZnSO4, 7H2O (0.5 microg/ml). L-asparagine (0.2%) and sodium dodecyl sulfate (1.0 microg/ml). The possible relationship between the rhizobial IAA production and legume-rhizobia symbiosis is discussed.