Purification and characterization of hydroperoxide lyase from amaranth tricolor (Amaranthus mangostanus L.) leaves

Hydroperoxide lyase (HPL) was extracted from amaranth tricolor leaves using Triton X-100, and purified to electrophoretic homogeneity by ammonium sulfate precipitation, ion-exchange chromatography, hydrophobic interaction chromatography and hydroxyapatite chromatography. The purified HPL preparation consisted of a single band and spot with a molecular mass of about 55 kDa as shown in SDS–PAGE and 2-D PAGE, respectively; the isoelectric point was found to be about 5.4. The maximum activity of the enzyme was observed at pH 6.0 and 25 °C, respectively. The HPL showed higher activity against 13-hydroperoxy-linolenic acid compared to 13-hydroperoxy-linoleic acid. K _m value for 13-hydroperoxy-linolenic acid was 62.7 μM, and the corresponding V _max was 178.5 μM min⁻¹. The activity of HPL was significantly inhibited by nordihydroguaiaretic acid, HgCl₂ and 2(E)-hexenal but not by EDTA and hexanal.     

Purification of isocitrate lyase from Saccharomyces cerevisiae

Isocitrate lyase purified to homogeneity from Saccharomyces cerevisiae was composed of four identical subunits with a molecular mass of 75 kDa. The enzyme was most active at pH 7.0 in the presence of 5 mM-Mg2+. The Km value for threo-Ds-isocitrate was 1.4 mM. Isocitrate lyase was shown to be thermostable at 50 degrees C for 60 min at a high salt concentration, but rapidly lost activity at -20 degrees C or by dialysis.     

Efficient generation of 2E-hexenal by a hydroperoxide lyase from mung bean seedlings

2E-hexenal was generated with a high molar conversion rate by the incubation of a hydroperoxide lyase containing extract from mung bean seedlings and its substrate, 13-hydroperoxy-9Z, 11E, 15Z-octadecatrienoic acid (13-HPOT). Various parameters affected the yield of 2E-hexenal and the conversion rate: hydroperoxide lyase activity was especially, pronounced in seedlings older than 10 days. The cleavage of 13-HPOT by a solubilized enzyme extract proceeded best at pH 6.5. Time-course studies showed that the majority of flavour compounds was already generated during the first 10 min of the incubation period. Using optimized reaction conditions, a maximum yield of 1062 mg kg⁻¹ 2E-hexenal was obtained with 32.6 mmol kg⁻¹ (10.1 g kg⁻¹) 13-HPOT. However, the conversion rate was highest (maximum 86.3%) at a low substrate concentration, indicating a suicidal behaviour of the hydroperoxide lyase. Enzymatically hydrolyzed and dioxygenated linseed oil was a suitable alternative to pure linolenic acid.     

氢过氧化物裂解酶合成己烯醛反应的研究

以苋菜作为氢过氧化物裂解酶（HPL）的酶源,研究了氢过氧化物裂解酶合成己烯醛的反应,并通过顶空-气相联用法（HS-GC）对产物进行分析。该反应中HPL对产物具有较强的吸附作用,大大影响了产物测量的准确度。通过一个校正方法来减少误差,并在此基础上考察了该反应的反应时间、pH、温度、底物浓度、酶浓度、BHT浓度等因素对己烯醛产率的影响,其中当反应时间10min,pH7.5,温度20℃,40mmol/L底物,酶浓度为12U/mL,BHT浓度为1mmol/L时,己烯醛的产率达到985mg/L。     

Stability of hydroperoxide lyase activity from Amaranthus tricolor (Amaranthus mangostanus L.) leaves: influence of selected additives

BACKGROUND: Hydroperoxide lyase (HPL) has potential value for the flavour additive industry. Currently, the production and application of HPL suffer from stability problems. The objective of this study was to investigate the stabilisation of HPL preparation from Amaranthus tricolor leaves by the addition of selected chemical additives. RESULTS: Amaranthus tricolor leaves were identified as a particularly rich source of 13‐HPL activity. The addition of 100 g L^?1 sucrose and trehalose to microsomal HPL prior to lyophilisation could retain nearly 100% enzymatic activity, compared to only 20% for the lyophilised control. The lyophilised microsomal HPL containing sucrose maintained full activity for even 40 days storage at ? 20 °C. For HPL solution, glycerol was effective for long‐term stability at ? 20 °C. Moreover, poyols (sucrose and trehalose) and amino acid (glycine) enhanced the thermostability of HPL, while KCl and polyol mannitol decreased the thermostability of HPL. CONCLUSION: The flavour‐producing enzyme HPL, found in the leaves of Amaranthus tricolor, was stabilised by the addition of chemical additives. Copyright © 2010 Society of Chemical Industry     

Production of (2E)-hexenal by a hydroperoxide lyase from Amaranthus tricolor and salt-adding steam distillation for the separation

(2E)-Hexenal is widely used in flavors and perfumes; however, it is mainly derived from chemical synthesis. In this study, hydroperoxide lyase (HPL) naturally originated from Amaranthus tricolor was used to catalyze the reaction to generate (2E)-hexenal from 13-hydroperoxy-9Z, 11E, 15 Z-octadecatrienoic acid (13-HPOT), and salt-adding steam distillation was used for the separation of (2E)-hexenal. A maximum yield of (2E)-hexenal that reached 1,156.4?mg?L^?1 was obtained with a high substrate concentration (40?mM 13-HPOT) under the following conditions: 10?min, pH 7.5, 20?°C, HPL 16 U?mL^?1, butylated hydroxytoluene (BHT) 1?mM, and dithiothreitol (DTT) 15?mM. Then the separation of (2E)-hexenal was conducted by salt-adding steam distillation. It was found that AlCl₃ had the greatest effect on the separation of (2E)-hexenal, followed by CaCl₂ and NaCl. The distillate yield with the addition of AlCl₃ was 93.2?%, while the distillate yield without the addition of salt was 81.2?%. The distillate concentration with AlCl₃ was 6,464.2?mg?L^?1, while the distillate concentration without the addition of salt was 4,490.3?mg?L^?1. The addition of salt improved the efficiency of the steam distillation. This study was greatly meaningful for providing a green method to the large-scale production of (2E)-hexenal.     

刺参多糖的提取纯化及其组分的分析

目的研究圈养刺参多糖的组成。方法以大连圈养刺参为研究对象,采用酶解醇沉法提取刺参的粗多糖,并通过DEAE-Sepharose Fast Flow阴离子交换树脂进行进一步纯化,并分别采用高效液相色谱法和红外光谱法对多糖的单糖组成及其含量和多糖的结构进行分析。结果提取的刺参粗多糖含量为62.30%,蛋白质含量为14.27%,纯度较好,经纯化后得到的三个组分峰(峰1、峰2和峰3),除甘露糖外,组分峰2和组分峰3中各单糖含量间均存在显著性差异(P0.05),且组分峰3多糖的质量比最高,为36.45%;刺参多糖中的单糖以岩藻糖、氨基半乳糖、葡萄糖醛酸为主,除葡萄糖外,组分峰3中的其他单糖含量均高于组分峰2;组分峰3的结构较复杂。结论本文为海参多糖的开发与利用提供了技术支撑。     

河北省设施黄瓜农药残留风险评估

目的 明确河北省设施黄瓜农药残留状况和居民的膳食摄入风险情况。方法 对采自主产区的90份设施黄瓜样品进行农药残留检测,分别通过%ADI 和%ARfD 进行农药残留慢性膳食摄入风险评估和急性膳食摄入风险评估,借鉴英国兽药残留委员会兽药残留风险排序矩阵进行风险排序。结果 检测的87种农药中有26 种农药检出残留,检测的90份样品的阳性样品比率为100.0%。不同人群慢性膳食摄入风险(ADI%)在0.00%～17.58%之间,急性膳食摄入风险(%ARfD)在0.06%～54.29%之间。根据残留风险得分,高风险农药有3种,即阿维菌素、联苯菊酯和毒死蜱。结论 河北省设施黄瓜农药残留检出率较高,仅有1个样品农药残留超标。农药残留对居民的膳食摄入风险均很低,没有健康风险。建议优先登记盐酸吗啉胍等抗病毒药物在黄瓜上的使用,并制定盐酸吗啉在黄瓜上的MRL值。     

乳酸黄瓜的腌制

本文对乳酸黄瓜的腌制方法进行了研究和探讨，利用多菌株乳酸菌菌液腌制黄瓜，不仅使酸黄瓜的酸味更加纯正，而且提高营养价值，本方法适合于酸黄瓜等生产企业技术升级和产品内在质量的提高。     

硅胶吸附脱除注射用大豆油氢过氧化物的研究

开展了硅胶吸附脱除注射用大豆油氢过氧化物的研究。以过氧化值为评价指标,筛选硅胶种类,优化吸附工艺参数,并对吸附脱除氢过氧化物后的注射用大豆油的其他质量指标进行评价。结果表明,最佳吸附工艺条件为:选用粒度为70~200μm的进口硅胶,硅胶添加量11%,反应温度60℃,反应时间1. 0 h。在最佳工艺条件下,注射用大豆油的过氧化值、酸价、皂化值、碱性杂质、不皂化物等指标均符合注射用大豆油国家标准。     

3种低值海参中海参多糖的提取分离及化学组成研究

海参是我国重要的经济水产品,具有多种营养及生理调节功能。海参多糖是海参的主要功效成分之一。文中以3种低值海参-黄玉参(Stichopus naso)、沙参(Holothuria floridana)及土耳其参(Holothuria tubulosa)为实验原料,在利用分子生物学方法确认其种属的基础上,提取其中的海参多糖,并利用阴离子交换层析分离纯化出海参硫酸软骨素及海参岩藻聚糖硫酸酯2种组分。分别采用柱前衍生-HPLC法、离子色谱法及高效凝胶排阻色谱法分析各样品的单糖组成、硫酸根含量及分子质量。结果表明:海参多糖及其组分的化学组成随海参来源的不同而存在差异。     

Molecular cloning,expression, and enzymatic characterization of <Emphasis Type="Italic">Solanum tuberosum</Emphasis> hydroperoxide lyase

A cDNA encoding hydroperoxide lyase (HPL) was isolated from Solanum tuberosum, cloned into pQE-30 vector, and expressed in E. coli. The recombinant protein was purified by nickel affinity chromatography and showed an approximate molecular weight of 54 kDa by SDS–PAGE analysis, which was similar to the predicted value based on the putative amino acid sequences (53.9 kDa). 13-Hydroperoxy-linolenic acid (13-HPOT) was the preferred substrate for the enzyme compared with 13-hydroperoxy-linoleic acid (13-HPOD). The corresponding volatile products were 2(E)-hexenal and n-hexanal tested by headspace-gas chromatography, respectively. The enzyme was optimally active at 25 °C and pH 6.5. The K _m, V _max, and the catalytic efficiency (V _max/K _m) for 13-HPOT were 56.6 μM, 71.3 units/mg, and 1.26 units/mg · μM, respectively. Activity of the recombinant potato HPL increased when Triton X-100, sodium chloride, or potassium chloride was added in the reaction mixture, while calcium chloride decreased activity of the recombinant enzyme.     

Report of illnesses caused by aldicarb-contaminated cucumbers

During May and June of 1985 the Health Protection Branch and several other agencies were involved in the investigation of over 300 reports of illness reported in the Vancouver area of British Columbia, Canada. Symptoms reported included nausea, vomiting, dizziness, muscle fasciculation and blurred vision. A review of the onset of symptoms and food consumed suggested that at least 140 people had become ill from eating cucumbers adulterated with a carbamate pesticide. The presence of residues of aldicarb in cucumbers from one particular producer was confirmed by laboratory analysis.     

海参加工产品开发现状及研究进展

海参具有抗肿瘤、抗凝血、抗氧化和调节免疫力等多种生理功能,有很高的食用和药用价值,在营养保健方面备受重视。国内外对海参内脏的开发利用研究较少,对海参内脏的活性成分缺乏认识,并且海参内脏往往作为加工副产物而被随意丢弃,得不到充分利用。目前,海参内脏的利用主要集中于活性成分的鉴定和产品的脱腥,对产品的开发研究较少。本文以海参内脏的营养物质及活性成分为导向,从论文、授权专利和保健食品三个方面,阐述了海参肠、卵、精、生殖腺和海参内脏的加工利用、脱腥方法的建立以及潜在的产品开发方向。总体而言,目前普遍存在海参内脏活性成分加工方式不统一,保健食品效用成分不明确等缺点。随着加工技术的发展,运用酶解、提取等手段对海参内脏进行综合利用将成为重要方向。     

Chemical composition and nutritional quality of sea cucumbers

BACKGROUND: The dried form of sea cucumbers has been a seafood and medicinal cure for Asians over many centuries. In this study the chemical composition and nutritional quality of eight common sea cucumbers (Stichopus herrmanni, Thelenota ananas, Thelenota anax, Holothuria fuscogilva, Holothuria fuscopunctata, Actinopyga mauritiana, Actinopyga caerulea and Bohadschia argus) were determined. RESULTS: All species except T. anax and A. caerulea had higher protein and lower fat levels. A. mauritiana and B. argus had less ash content. Glycine was the dominant amino acid found in all species, and content ranged from 126 to 216 mg g^?1 of crude protein. All species exhibited low lysine:arginine ratio and higher essential amino acid scores were obtained by threonine and phenylalanine + tyrosine. A. mauritiana had proportionally less saturated fatty acids (31.23%), and more monounsaturated fatty acids (45.64%) and polyunsaturated fatty acids (PUFA, 23.13%) than other species. Arachidonic acid (C20:4n‐6) was the major PUFA in all species. T. ananas, A. mauritiana and A. caerulea contained more n‐3 PUFA. The n‐3/n‐6 ratios of eight sea cucumbers species ranged from 0.25 to 0.61. CONCLUSION: Sea cucumbers are a seafood with high protein and low fat levels. The amino acid contents were similar but fatty acid profiles were different among species. The comparison showed that T. ananas, A. mauritiana and B. argus possessed higher nutritional values than other sea cucumber species. Copyright © 2010 Society of Chemical Industry     

不同品种黄瓜中脂肪酸的研究

采用索氏提取法对不同品种黄瓜中脂肪酸进行了提取,以气相色谱-质谱联用仪进行了分析,由水黄瓜﹑旱黄瓜和水果黄瓜中分别分离鉴定出11种﹑5种和11种脂肪酸,并对其主要成分进行了鉴定,主要化学成分均为:9,12-十八碳二烯酸和9,12,15-十八碳三烯酸。     

钙制剂涂膜黄瓜保鲜的研究

以钙制剂对黄瓜进行涂膜处理,于室温下贮藏,测定了在贮藏过程中黄瓜的失重率、叶绿素、Vc、呼吸强度以及硬度的变化。实验结果表明,以6倍稀释液浓度涂膜黄瓜,其保鲜效果较好,可以有效延长黄瓜的货架期。     

壳聚糖涂膜处理黄瓜保鲜作用的研究

本文旨在筛选不同浓度的壳聚糖用于黄瓜的涂膜保鲜。通过本次实验结果表明，采用1．0％和1．5％浓度的壳聚糖并辅之低温处理黄瓜的贮藏保鲜期内，实验果蔬能很好保持其质地、外观和营养成分。