鸭毛梗制备复合氨基酸工艺条件的研究

采用正交试验方法 ,研究了鸭毛梗水解制备复合氨基酸的工艺条件 ,结果表明 :温度 /压力是影响氨基酸转化率最主要的因素。鸭毛梗水解制备的复合氨基酸转化率盐酸法最高 (82 .36 % ) ,氢氧化钠法最低 (5 8.4 6 % ) ,硫酸法与盐酸法接近(79.4 4 % )。硫酸法产率较高 ,操作方便 ,环境污染和设备腐蚀均小 ,适合大量生产 ,确定为水解制备复合氨基酸介质 ,其最佳工艺条件为 :水解时间 8.0h ,硫酸浓度 3.0mol·L-1,水解温度 12 5℃。氨基酸分析表明 ,水解液中均含有 18种以上氨基酸。     

不同品种魔芋精粉中氨基酸含量分析研究

花魔芋和白魔芋精粉中均含有 18种水解氨基酸和 18种游离氨基酸 ,前者水解氨基酸的总量为 2 .4 4 % ,其中必须氨基酸质量分数为 0 .6 2 % ,游离氨基酸总量为 1.10 % ,其中游离必须氨基酸质量分数为 0 .33% ;后者水解氨基酸总量为 2 .0 1% ,其中必须水解氨基酸质量分数为 0 .5 6 % ,游离氨基酸总量为 0 .4 1% ,其中必须游离氨基酸质量分数为 0 .13%。提示白魔芋和花魔芋精粉中氨基酸含量略有差异 ,但此差异不大 ,其品质 ,营养价值及特性等主要取决于魔芋精粉中主要成分葡甘聚糖的含量     

由铬革屑制备可溶性蛋白及氨基酸的研究

成品铬革屑中蛋白质含量在 70 %以上 ,处理成小颗粒后与水、Ca(OH) 2 按 1∶4 0∶0 .4的比例混合 ,90℃反应 5h ,可溶性蛋白转化率近 6 0 % ,且在升温后加入Ca(OH) 2 有利于退鞣。以 6mol/L盐酸水解皮革蛋白粉制备复合氨基酸 ,水解 14h ,水解液以HD -I树脂脱色 ,氨基酸损失较少 ,且动态脱色效率明显高于静态脱色 ,采用 717树脂脱酸可获得pH4 .5 - 5的复合氨基酸溶液 ,总得率为 6 0 .1%。     

脑蛋白粉的制备及其酶解方法的研究

研究了以鲜猪脑制备蛋白粉并进行酶水解的方法 ;脑蛋白粉质量、不同酶和加酶方法对水解结果的影响 ;分析了水解液中游离氨基酸和低分子肽谱 ,并与国内外类似研究进行了比较。结果表明 :丙酮、乙醚沉淀制得的脑蛋白粉含氮 9.0 %～ 1 1 .5% ,脂肪 2 .5%～ 4 .0 % ,适于酶解 ;水解液含有 1 6种游离氨基酸 ,总量达 3 2 .4 4mg/ml和 4个分子量小于 1万的肽。提出精制脑蛋白粉进行水解、减压浓缩、超滤是提高水解液有效成分的技术措施。     

脑蛋白粉的制备及其酶解方法的研究

研究了以鲜猪脑制备蛋白粉并进行酶水解的方法 ;脑蛋白粉质量、不同酶和加酶方法对水解结果的影响 ;分析了水解液中游离氨基酸和低分子肽谱 ,并与国内外类似研究进行了比较。结果表明 :丙酮、乙醚沉淀制得的脑蛋白粉含氮 9.0 %～ 1 1 .5% ,脂肪 2 .5%～ 4 .0 % ,适于酶解 ;水解液含有 1 6种游离氨基酸 ,总量达 3 2 .4 4mg/ml和 4个分子量小于 1万的肽。提出精制脑蛋白粉进行水解、减压浓缩、超滤是提高水解液有效成分的技术措施。     

二次中和法制取菜籽复合氨基酸新工艺研究

为得到高质量的菜籽复合氨基酸,以脱皮菜籽粕为原料,研究了硫酸水解制备复合氨基酸的新工艺一二次中和法,解决了氨基酸脱色和副产品植酸的利用问题。水解的最佳工艺参数是3mol·L-1的H2SO4水解18h;ca(OH)2作中和剂,第一次中和和脱色的最佳pH为2-4,第二次中和的最佳pH为6.5-7.0,中和后的溶液经减压浓缩,喷雾干燥,制得菜籽复合氨基酸。复合氨基酸得率≥40％,纯度≥40％;副产品植酸钙得率10％左右,纯度40％-50％。     

不同生态系统土壤氨基酸氮的组成及含量

采集于内蒙古白音锡牧场、陕西澄城、杨凌、宜川和太白山等地不同生态系统的 1 2个土样 ,用 6 mol/ L HCl水解 ,经 H型酸性阴离子交换树脂柱纯化后 ,用 Beckman 1 2 1 MB型氨基酸分析仪测定了 1 7种常见氨基酸。测定结果表明 ,不同生态系统土壤酸解氨基酸含量有很大差异 ,表现为草甸土壤 (氨基酸含量为 2 2 83.9μg N/ g) >森林土壤 ( 1 733.6μg N/g) >草原土壤 ( 85 6 .3μg N/ g) >农田土壤 (平均为 2 4 8.5± 37.8μg N/ g) ,并且氨基酸氮与土壤全氮有极显著的正相关关系 ( p<0 .0 1 ) ;在氨基酸中以中性氨基酸所占比例最大 ,平均为 5 3.99% ,其次为碱性和酸性氨基酸 ,分别为 2 4 .94 %和2 0 .5 9% ,含硫氨基酸最少 ,仅为 0 .4 8% .游离氨基酸以草甸土壤最高 ,为 1 4 .5 8μg N/ g,其它土壤在 1 .1 4～ 8.6 7μg N/ g之间 ,大部分在 2～ 3μg N/ g。游离氨基酸不仅数量低 ,而且种类也比酸解氨基酸少。不管是酸解氨基酸 ,还是游离氨基酸 ,在 0～ 2 0 cm土层的含量均大于 2 0～ 4 0 cm土层 ,从不同土壤样品的平均结果看 ,对酸解氨基酸 ,0～ 2 0 cm土层为96 0 .9μg N/ g,2 0～ 4 0 cm土层为 5 2 8.9μg N/ g ;对游离氨基酸氮 ,0～ 2 0 cm土层 6 .2 8μg N / g,2 0～ 4 0 cm土层 2 .2 2μgN/ g。施用氮     

不同栽培料培育的茶薪菇氨基酸含量比较研究

木屑栽培茶薪菇和稻草培茶薪菇均含有 18种氨基酸 ,前者氨基酸总量为 18.35 % ,其中必须氨基酸质量分数为 8.14% ,鲜味氨基酸质量分数为 5 .88% ;后者氨基酸总量为 2 0 .2 1% ,其中必须氨基酸质量分数为 8.96 % ,鲜味氨基酸质量分数为 6 .37%。提示稻草栽培茶薪菇的氨基酸营养价值优于木屑栽培茶薪菇     

黄鳝含肉率及氨基酸成分分析

测定了黄鳝的含肉率及其氨基酸含量 ,对其营养价值进行了评定。该鱼 (鲜样 )含肉率 75 .12 % ;水分 6 2 .9% ;肌肉粗蛋白 (g/10 0g干样 ) 74.5 6 % ;水解氨基酸总量 5 6 .11% ;其中必需氨基酸 2 0 .83% ;占氨基酸总量的 37.12 %。认为黄鳝是一种营养价值和养殖价值都比较高的淡水养殖鱼类 ,具有良好的开发利用前景。     

南美鲱鱼的含肉率及肌肉营养评价

测定了 6尾南美鲱鱼的含肉率及其营养成分 ,并对其营养价值进行综合评定。该鱼 (鲜样 )含肉率 83.6 5 % ;肌肉中含粗蛋白 1 7 74 % ,粗脂肪 5 2 5 % ,粗灰分 1 0 2 % ,水分 74 73% ,无氮浸出物 1 2 6 %。干物质中水解氨基酸总量 70 36 % ,其中必需氨基酸 2 7 90 % ,占氨基酸总量的 39 6 5 % ;游离氨基酸总量1 2 6 5 1 8mg 1 0 0g;必需氨基酸指数为 4 0 33;矿物质含量丰富 ,尤其是硒。认为南美鲱鱼是一种营养价值和养殖价值都比较高的淡水养殖新品种 ,具有良好的开发利用前景。     

Optimizing dilute acid hydrolysis of hemicellulose in a nitrogen-rich cellulosic material--dairy manure

Effective dilute acid hydrolysis of dairy manure which contains roughly 12% hemicellulose on a dry matter basis can produce a variety of mono-sugars such as arabinose, xylose and galactose, as well as to further benefit utilization of cellulose in the manure. To enhance the effectiveness of this dilute acid hydrolysis, the effect of manure nitrogen content was studied because some reactions such as the browning reaction between amino acids and reducing sugars and acid-base reactions involving ammonia and acid interfere with the hydrolysis. Two dairy manure samples were used to study this nitrogen effect; the original manure and the pretreated manure derived from a solid/liquid separation pretreatment. The pretreated manure had a total nitrogen content of 1.3% dry matter (DM) while the original dairy manure had twice that amount with a total nitrogen content of 2.6% DM. Results found that the optimal conditions for hydrolysis of manure hemicellulose were 2 h reaction time, 1% sulfuric acid concentration, 135 degrees C, and 10% sample concentration using the pretreated dairy manure as raw material. Under these conditions the corresponding sugar yield from hemicellulose was 111% and sugar concentration in the solution reached 16.5 g/l. At the same time, the hydrolyzed solid had 43% DM of cellulose, which was much higher than both the original manure containing 22% and the pretreated manure with 32%.     

Synthesis of 17O isotope labeled Leu-enkephalin and 17O n.m.r

Oxygen-17 isotope was introduced into the alpha-carboxyl group of glycine, 1-phenylalanine, 1-leucine and 1-tyrosine by acid catalyzed exchange of 17O from H2O(17) or by acid hydrolysis of respective amino acid methyl esters in H2O(17). Quantitative enrichment of glycine was achieved by acid hydrolysis of amino acetonitrile in H2O(17). For alpha-amino protection in amino acids t-butoxycarbonyl (Boc) group was employed for 17O labeled enkephalin synthesis. Five analogues of Leu-enkephalins (I-V) labeled with 17O at different amino acid residues were synthesized by solid phase method. 17O n.m.r. spectra were measured at 24.4 and 67.8 MHz for Leu-enkephalins 17O labeled at Gly2 and Phe4 positions. A downfield shift was observed for 17O labeled Gly2 Leu-enkephalin upon heating. This shift is indicative of the rupture of intramolecular hydrogen bonds. The preliminary results confirm the hypothesis that an intramolecular hydrogen bond exists between the carbonyl group of Gly2 and NH group of Leu5.     

Acid hydrolysis of protein in a microcapillary tube for the recovery of tryptophan

The acid hydrolysis of proteins was miniaturized and simplified by employing microcapillary tubes (100 microl in volume) with 6 M HCl containing 1% 2-mercaptoethanol and 3% phenol for an amino acid compositional analysis. The method not only eliminated the laborious evacuation step for the hydrolysis tube but also decreased the destruction of tryptophan during hydrolysis. The recovery of tryptophan was 79% by acid hydrolysis at 145 degrees C for 4 h. Since the acid mixture could be removed under vacuum, the hydrolysate was subjected to an amino acid analysis without neutralization or dilution.     

Acidogenic fermentation of proteinaceous solid waste and characterization of different bioconversion stages and extracellular products

The purpose of this study was to investigate hydrolysis of animal fleshing (ANFL), a predominant tannery solid waste and to characterize the acetogenic fermentation products of anaerobic digestion. The acidogenic digestibility of the tannery solid wastes were evaluated up to 120 h using batch anaerobic digestion tests performed under mesophilic condition at 37 degrees C. The degradation of ANFL starts with non-fibrillar proteins and proceeds with fibrillar proteins. The release of aliphatic amino acid in the early stages of hydrolysis (24 h) and followed by aromatic amino acids (24-72 h) were evidenced by HPLC analysis. The maximum production of propionic and valeric acid were observed in 72 h followed by rapid increase in acetic acid in 96 h using GC-MS. Breakdown of ANFL and formations of other metabolites were evidenced by FT-IR and (1)H-NMR spectroscopy.     

Novel formation of alpha-amino acids from alpha-oxo acids and ammonia in an aqueous medium

In the course of a study of possible mechanisms for chemical evolution in the primeval sea, we found the novel formation of alpha-amino acids and N-acylamino acids from alpha-oxo acids and ammonia in an aqueous medium. Glyoxylic acid reacted with ammonia to form N-oxalylglycine, which gave glycine in a 5-39% yield after hydrolysis with 6N HC1. Pyruvic acid and ammonia reacted to give N-acetylalanine, which formed alanine in a 3-7% overall yield upon hydrolysis. The pH optima in these reactions were between pH 3 and 4. These reactions were further extended to the formation of other amino acids. Glutamic acid, phenylalanine and alanine were formed from alpha-ketoglutaric acid, phenylpyruvic acid and oxaloacetic acid, respectively, under similar conditions. N-Succinylglutamic acid was obtained as an intermediate in glutamic acid synthesis. Phenylacetylphenylalanineamide was also isolated as an intermediate in phenylalanine synthesis. Alanine, rather than aspartic acid, was produced from oxaloacetic acid. These reactions provide a novel route for the prebiotic synthesis of amino acids. A mechanism for the reactions will be proposed.     

Optimization of H2SO4-catalyzed hydrothermal pretreatment of rapeseed straw for bioconversion to ethanol: Focusing on pretreatment at high solids content

A central composite design of response surface method was used to optimize H₂SO₄-catalyzed hydrothermal pretreatment of rapeseed straw, in respect to acid concentration (0.5–2%), treatment time (5–20 min) and solid content (10–20%) at 180 °C. Enzymatic hydrolysis and fermentation were also measured to evaluate the optimal pretreatment conditions for maximizing ethanol production. The results showed that acid concentration and treatment time were more significant than solid content for optimization of xylose release and cellulose recovery. Pretreatment with 1% sulfuric acid and 20% solid content for 10 min at 180 °C was found to be the most optimal condition for pretreatment of rapeseed straw for ethanol production. After pretreatment at the optimal condition and enzymatic hydrolysis, 75.12% total xylan and 63.17% total glucan were converted to xylose and glucose, respectively. Finally, 66.79% of theoretical ethanol yielded after fermentation.     

The preparation of matrix-bound proteases and their use in the hydrolysis of proteins

Four proteases, crude acid protease from Aspergillus, pronase, amino-peptidase M, and prolidase, have been covalently attached to activated agarose and to amino propyl glass beads. The matrix-bound enzymes have been tested as catalysts for the complete hydrolysis of protein substrates, with the primary goal to isolate unstable amino acid derivatives present in the substrate protein. Under conditions used in the present work, the total amino acid release from the protease-catalyzed hydrolysis of four substrate proteins (pancreatic ribonuclease, egg white lysozyme, yeast enolase, and bovine insulin) was 95–103% of that observed in standard acid hydrolysis. Recovery of individual amino acids showed greater deviation from the theoretical values, but cystine was the only amino acid recovered in low yields (42–77%) from all four proteins. Derivatized amino acids, such as methionine sulfoxide, O-(butylcarbamoyl)-serine, and N-glycosyl asparagine have been obtained from chemically modified proteins or from unmodified glycoprotein in good yield, and normal amino acid constituents of proteins which cannot be quantified after acid hydrolysis (tryptophan, asparagine, and glutamine) have also been determined either directly after proteolysis or after proteolysis in conjunction with acid hydrolysis.     

氨基酸分析仪测定饲料添加剂——叶酸的方法

用６ｍｏｌ／Ｌ盐酸于１１０℃条件下水解饲料添加剂——叶酸,使之游离出谷氨酸,用氢氧化钠中和调节ｐＨ到２,氨基酸分析仪测定谷氨酸含量,经与标准叶酸水解样品比较,计算出叶酸的纯度。该方法重现性好,变异系数ＣＶ＝０．０８％,平均回收率为９８．３４％,浓度与峰面积呈线性相关,相关系数ｒ＝０．９９８７,可随氨基酸分析同时进行,不需改变任何分析条件。     

Ultrasound‐assisted dilute acid hydrolysis of tea processing waste for production of fermentable sugar

Lignocellulosic materials that are the most abundant plant biomass in the world have the potential to become sustainable sources of the produced value added products. Tea processing waste (TPW) is a good lignocellulosic source to produce the value added products from fermentable sugars (FSs). Therefore, the present study is undertaken to produce FSs by using ultrasound‐assisted dilute acid (UADA) and dilute acid (DA) hydrolysis of TPW followed by enzymatic hydrolysis. UADA hydrolysis of TPW was optimized by response surface methodology (RSM) at maximum power (900 W) for 2 h. The optimum conditions were determined as 50°C, 1:6 (w/v) solid:liquid ratio, and 1% (w/v) DA concentration, which yielded 20.34 g/L FS concentration. Furthermore, its DA hydrolysis was also optimized by using RSM for comparison and the optimized conditions were found as 120°C, 1:8 solid:liquid ratio, and 1% acid concentration, which produced 25.3 g/L FS yield. Even though the produced sugars with UADA hydrolysis are slightly less, but it can provide significant cost saving due to the lower temperature requirement and less liquid consumption. Besides, enzymatic hydrolysis applied after pretreatments of TPW were very more economic than the conventional enzymatic hydrolysis in the literature due to shorter time requiring. In conclusion, ultrasound‐assisted is a promising technology that can be successfully applied for hydrolysis of biomass and can be an alternative to the other hydrolysis procedures and also TPW can be considered as suitable carbon source for the production of value‐added products like biofuels, organic acids, and polysaccharides. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:393–403, 2016     

Optimization of enzymatic hydrolysis of visceral waste proteins of Catla (Catla catla) for preparing protein hydrolysate using a commercial protease

Protein hydrolysate was prepared from visceral waste proteins of Catla (Catla catla), an Indian freshwater major carp. Hydrolysis conditions (viz., time, temperature, pH and enzyme to substrate level) for preparing protein hydrolysates from the fish visceral waste proteins were optimized by response surface methodology (RSM) using a factorial design. Model equation was proposed with regard to the effect of time, temperature, pH and enzyme to substrate level. An enzyme to substrate level of 1.5% (v/w), pH 8.5, temperature of 50 degrees C and a hydrolysis time of 135 min were found to be the optimum conditions to obtain a higher degree of hydrolysis close to 50% using alcalase. The amino acid composition of the protein hydrolysate prepared using the optimized conditions revealed that the protein hydrolysate was similar to FAO/WHO reference protein. The chemical scores computed indicated methionine to be the most limiting amino acid. The protein hydrolysate can well be used to meet the amino acid requirements of juvenile common carp and hence has the potential for application as an ingredient in balanced fish diets.