四川麸醋发酵过程中有机酸及游离氨基酸含量变化分析

为了解四川麸醋发酵过程中有机酸及游离氨基酸含量的变化规律,采用高效液相色谱和氨基酸自动分析仪对发酵过程中7种有机酸及17种游离氨基酸含量进行测定。结果表明,四川麸醋发酵过程中含量最高的2种有机酸为乙酸和乳酸,随着发酵的进行,其含量显著增加;草酸、柠檬酸、酒石酸、苹果酸、琥珀酸含量较低,在发酵过程中含量略有变化。游离氨基酸含量随着发酵的进行呈增加趋势,从发酵初期668mg/100g增至1 470 mg/100g,其中天门冬氨酸、丝氨酸、谷氨酸、甘氨酸、丙氨酸、缬氨酸、组氨酸、异亮氨酸、酪氨酸、脯氨酸对四川麸醋风味形成具有较大的贡献。     

3株酿酒酵母发酵过程中有机酸含量变化分析

通过高效液相色谱法对3株酿酒酵母(Saccharomyces cerevisiae)发酵过程中葡萄糖、甘油、乙醇及有机酸含量进行测定分析。结果表明:S.cerevisiae1946发酵体系中甘油和乙醇的含量显著高于S cerevisiae P1和S.cerevisiae 32788发酵体系(P0.05);3株酿酒酵母发酵液中7种有机酸存在明显的差异性和规律性;S.cerevisiae 1946发酵体系中有机酸的含量低于S.cerevisiae P1和S.cerevisiae 32788发酵体系,S cerevisiae的产酸水平与产乙醇能力呈负相关关系。     

低温乳酸菌发酵泡白菜有机酸和游离氨基酸含量分析

10℃条件下,以2株耐低温乳酸菌3m-1(Lactobacillus plantarum)和8m-9(Leuconostocmesenteroides)为菌种,比较2种接菌发酵和老盐水发酵泡白菜有机酸和游离氨基酸含量的变化规律。结果表明,不同方式发酵的泡白菜均检出6种有机酸和17种氨基酸;低温乳酸菌接种发酵泡白菜与老盐水发酵泡白菜中的有机酸和游离氨基酸含量的变化趋势基本一致,与老盐水发酵泡白菜相比,低温乳酸菌接种发酵泡白菜的有机酸和游离氨基酸含量更为丰富。其中,苹果酸、柠檬酸、琥珀酸含量相对较高。3种发酵方式生产的泡白菜产品中的EAA/TAA分别为48.41%、49.49%、29.91%。     

红枣白兰地发酵过程中酒醅氨基酸和有机酸的变化分析

利用高效液相色谱法(HPLC)对红枣白兰地酒醅发酵过程中的氨基酸和有机酸含量,及发酵过程中酒度、酸度的动态变化进行了分析研究。研究表明:红枣白兰地发酵酒醅中检测到16种氨基酸和7种有机酸,其中脯氨酸、天冬氨酸、谷氨酸是红枣白兰地发酵的主要氨基酸,发酵过程中平均含量分别为39.749、35.477、11.888 mg/g;乙酸、苹果酸、乳酸是红枣白兰地发酵的主要有机酸,在发酵结束时含量分别为8.189、4.243、3.646 mg/g。发酵过程中,氨基酸和有机酸整体含量呈增长趋势;甜味氨基酸和鲜味氨基酸为总氨基酸含量的45.39%、35.79%,苦味氨基酸含量较低,酒醅中氨基酸是红枣白兰地中风味成分的重要前体物质,并赋予红枣白兰地柔和的风味;比例协调的有机酸有利于增强酒的醇厚口感。      

鱼腐乳发酵过程中游离氨基酸含量及抗氧化活性的变化

利用总状毛霉（Mucor racemosus）和红曲霉（Monascus）F1对鱼豆腐进行发酵研制鱼腐乳,对鱼腐乳发酵过程中的游离氨基酸及抗氧化活性的变化规律进行分析。结果表明：在发酵过程中,鲜味氨基酸、必需氨基酸、疏水氨基酸、总氨基酸的含量都呈逐渐升高的趋势,在后熟第28天时分别达到了138.57 mg/100 g、491.68 mg/100 g、340.06 mg/100 g、915.77 mg/100 g。在发酵过程中DPPH自由基清除率和羟自由基清除率也呈逐渐升高的趋势,在后熟第28天时分别达到70.30%和63.11%,分别比发酵开始时提高了53.09%和24.14%。     

氨基酸、有机酸发酵过程中的生物传感器

介绍了目前应用于国内氨基酸工业、有机酸工业发酵中的生物传感器。根据其检测原理和主要性能指标与传统检测方法相比具有准确、快捷、节约检测成本、获得在线效益、指导生产的诸多优点。     

河鲀发酵鱼酱游离氨基酸分析

从游离氨基酸的含量和种类分析,谷氨酸、丙氨酸、苯丙氨酸、缬氨酸是河鲀发酵鱼酱的主要呈鲜氨基酸.比较不同接菌方式,无论是游离氨基酸总量,还是呈鲜味氨基酸含量,均表现出复合菌发酵组优于单菌种发酵组,接菌发酵组较未接菌自然发酵组成效更优.     

自然发酵酸菜游离氨基酸的分析

以自然发酵酸菜为研究对象,利用氨基酸自动分析仪,对酸菜中游离氨基酸的种类及含量进行了测定。结果表明,酸菜中富含17种呈味氨基酸,总含量达635 mg/L。其中,苏氨酸含量最高,其次是谷氨酸、丙氨酸、丝氨酸、缬氨酸和天门冬氨酸等。酸菜中含有7种为人体必需氨基酸,其含量占氨基酸总含量的41.73%。这些呈味氨基酸对酸菜特有风味的形成,具有重要作用。     

鲜食玉米发育过程中游离糖和氨基酸变化

以晶甜5号超甜玉米和晶糯8号糯玉米2个鲜食玉米品种为研究对象,采用高效液相色谱法测定并分析玉米鲜穗由吐丝授粉至乳熟期发育过程中3种游离糖和18种氨基酸的含量变化。结果显示,晶甜5号和晶糯8号2个品种的蔗糖和丙氨酸含量随发育时间延长均表现为低-高-低的变化趋势,并分别与3种游离糖和18种氨基酸总量的变化一致。对这2种玉米发育中测定的上述21个指标进行了主成分分析(principal components analysis,PCA)和聚类分析。PCA法提取了3个主成分,其贡献率分别为39.9%、24.4%和13.3%,其中PC1与PC2主要提取了鲜食玉米不同发育阶段甜味氨基酸及糖含量的变化信息,PC3则主要体现了2个品种中天冬氨酸与谷氨酸2种鲜味氨基酸含量的不同;聚类分析结果则显示玉米样品因发育阶段接近而聚集。综上所述,发育程度是影响鲜食玉米游离糖和氨基酸含量差异的主要因素,其次为品种间的差异。研究结果为从原料角度调控鲜食玉米加工产品品质尤其是玉米汁风味有良好的借鉴作用。     

韭黄发酵前后挥发性风味成分及游离氨基酸变化分析

为探究新鲜韭黄发酵前后风味成分及滋味特征的变化,采用顶空固相微萃取-气相色谱-质谱法（HS-SPME-GC-MS）和氨基酸分析仪对其挥发性风味成分和游离氨基酸进行测定,分析其风味和滋味特征,并通过滋味强度值（TAV）筛选特征呈味物质。结果表明,新鲜韭黄经发酵前后分别检出挥发性风味成分74种和76种,发酵前有机硫类40种、醛类16种、酯类7种、酸类1种、醇类3种和其他类7种,发酵后有机硫类17种、醛类11种、酯类32种、酸类5种、醇类4种和其他类7种。其中有机硫类化合物由40种减少至17种,酯类化合物由7种增加至32种,这是其风味成分变化的主要原因。韭黄发酵前检出游离氨基酸22种,其中包括8种必需氨基酸。发酵后检出游离氨基酸21种,其中包括7种必需氨基酸,发酵液中有4种苦味氨基酸TAV<1,表明通过发酵有效改善了韭黄滋味。     

Genome-wide analysis of coding DNA and amino acid variation in Saccharomyces cerevisiae

The possible causes of variation on amino acid composition in the yeast Saccharomyces cerevisiae were investigated genome-wide. The results indicated that: (a) the base composition of coding DNA and amino acid composition was similar among all the chromosomes, which was in sharp contrast with the great varies of the composition of the individual's coding DNA and amino acid; (b) some amino acids (e.g. Cys and Trp) were not present in all the proteins; and (c) amino acid bias was associated with a base bias (in terms of A-, G-, C- and T-rich codons). Based on the third rule and a proposed universal trend of amino acid gain and loss in protein evolution, the changing pattern of coding DNA was predicted to be T- and C-accruing, whereas A and G were consistently reducing. All these results held the potential to reveal precisely how DNA ongoing change has a major effect on the composition of proteins.     

酿酒酵母对弱有机酸胁迫的应激机制研究进展

酿酒酵母是生产酒类产品的主要微生物,而生产中的发酵环境对酿酒酵母来说是一种不利的生长代谢环境,存在多种胁迫因素,其中就包括弱有机酸引起的低pH胁迫。酿酒酵母应对胁迫环境,有自身一套完备的适应机制,不同胁迫应对机制既有相同之处亦有不同之处。本文概括了近年来酿酒酵母对弱有机酸应激机制的研究热点,主要从弱有机酸胁迫的基因表达、转录表达以及蛋白质表达3个水平进行阐述,涉及ATP结合区转运子Pdr12及其转录因子War1p,HOG-MAPK途径,水通道蛋白Fps1p,质膜H+-ATP酶,SOD,CAT,以及弱有机酸与其他胁迫的交互作用,旨在为更好地研究酿酒酵母的弱有机酸应激机制提供一定的参考。     

The cysteine transport system of Saccharomyces cerevisiae.

Although Saccharomyces cerevisiae strains had different cysteine uptake activities, they revealed monophasic uptake kinetics and had the same KT (83.3 microM). The optimal pH of cysteine uptake was between 4.5 and 5.0, but the activity was quickly lost if cells were kept in buffer. When the activity was measured in the growth medium, it increased in the presence of EDTA and greatly decreased in the presence of mercuric chloride. Thioglycol as well as metabolic inhibitors such as dinitrophenol and azide were inhibitory. Homocysteine and methionine were competitive and non-competitive inhibitors, respectively. Cysteamine and cysteic acid were not inhibitory. From these observations, we conclude that the system mediating uptake of cysteine is specific (we thus name it the cysteine transport system) and that the cysteine transport system recognizes not only the SH-group but also amino- and carboxyl-groups. In wild-type strains the cysteine transport system was derepressed only when the cells were incubated without any sulfur source. On the other hand, in cysteine-dependent mutants, cysteine uptake activity increased with increase of exogenous supply of cysteine, glutathione or methionine. From this result, we suspect that the cellular cysteine level is the limiting factor for biosynthesis of the cysteine transport system in cysteine-dependent strains.     

Regulation of the amino acid permeases in nitrogen-limited continuous cultures of the yeast Saccharomyces cerevisiae

In the yeast Saccharomyces cerevisiae, there is a general amino acid permease, regulated by nitrogen catabolite repression, and several specific permeases whose nitrogen regulation is not well understood. In this study, we used continuous cultures to analyse the effect of nitrogen limitation and pH on the activity of general and several specific amino acid permeases. General permease activity was maximal in severe nitrogen limitation and diminished 400-fold in cells grown under nitrogen excess. For the specific permeases, the maximal uptake activity was found between mild limitation and nitrogen excess, while very small activity was detected under strict limitation. These results indicate that the nitrogen regulation of the general and the specific amino acid carriers is coordinated in such a way that no redundancy exists in amino acid transport. The regulation of the specific permeases was similar to that found for a system with anabolic function in nitrogen metabolism. All of these permeases are supposed to work through a proton symport mechanism, and thus rely on pH gradients to carry out their function. We studied the effect of pH on the kinetic constants of the general permease. Our results show that the effect of pH on the K_m was different for acidic, neutral and basic amino acids, while the effect on V_max was independent of the electrical charge of the amino acids.     

不同代数酿酒酵母对有机酸代谢的影响

实验通过高效液相色谱法(HPLC)对酵母发酵液中6种有机酸测定分析,发现不同代数酵母发酵液中6种有机酸有明显的差异性和规律性。经过多次实验证明:五代以内的酵母活性较高,产有机酸的量较为规律、稳定,能够赋予酒类纯正的口感。     

富含谷氨酸酿酒酵母的筛选及发酵培养基优化

从农家自酿葡萄酒中筛选出一株富含谷氨酸酿酒酵母菌（Saccharomyces cerevisiae）F-5,其26S rDNA核苷酸序列与S. cerevisiae TY12的26S rDNA核苷酸序列同源性为100%。以胞内谷氨酸含量为目标,采用响应面法对其发酵培养基进行了优化,建立糖蜜、工业蛋白胨和KH2PO4的二次回归模型,确定培养基最佳配方为：糖蜜（含30%蔗糖）100 mL/L、酵母浸粉10 g/L、工业蛋白胨20 g/L、MgSO4·7H2O 1 g/L、KH2PO4 0.5 g/L、FeSO4·7H2O 2 g/L。在此优化培养基中发酵培养24 h,胞内游离谷氨酸达到了3.29%,比优化前提高了87.8%。     

葡萄酒酿造过程中氨基酸含量变化的研究

应用HPLC对我国4个产区多个品种葡萄酒酿造过程样品中氨基酸含量变化趋势进行了研究,结果表明,L-脯氨酸是所有葡萄汁中氨基酸的主体,也是各样品含量差异最大的氨基酸;红葡萄酒中含脯氨酸、苏氨酸、赖氨酸等20种氨基酸,其中以脯氨酸含量最高,发现不同葡萄品种之间游离氨基酸种类和含量有差别,这与葡萄品种、气候、发酵工艺有关。     

酿酒酵母ZGJ-1在猕猴桃果酒发酵中的研究及应用

为了将专利菌ZGJ-1在工业上进行广泛的应用并为猕猴桃产业开辟一条深加工新途径,分别以游离和固定化的酵母菌ZGJ-1为研究对象,采用单因素试验和正交试验,研究了猕猴桃果酒的最优发酵工艺条件。结果表明,固定化酿酒酵母ZGJ-1发酵果酒的最佳工艺参数为接种量5%,SO2添加量100 mg/L,起始糖度200 g/L。在此优化条件下,猕猴桃果酒酒精度为9.6%vol,残糖为32.28 g/L,发酵速度快,所产果酒香味浓郁,各项品质指标均达到相关国标标准。抗氧化能力试验结果表明,固定化酿酒酵母ZGJ-1发酵果酒对 ·OH、DPPH·、O2-·清除率分别为42%、96%、80%,显示其较好的抗氧化能力。