生物油脂酯-酯交换催化剂研究新进展

本文扼要论述生物油脂酯-酯交换催化剂国内外的最新研究现状,并对酶催化剂的优缺点进行了论述,同时对均相和多相化学催化剂的优缺点进行了分析,指出了存在的问题及今后的研究方向.     

Ca／Al复合固体碱催化剂用于生物柴油的制备

生物柴油可以由菜籽油与甲醇在碱催化剂的作用下通过酯交换反应制得。为解决生物柴油酯交换过程中的产物与催化剂分离问题。制备了Ca／趾复合固体碱催化剂，研究了反应条件对反应的影响。结果表明，该体系催化剂是制备生物柴油的良好非均相催化剂。生物柴油的最佳制备奈件为：催化剂质量分数为原料油的100／6，醇油摩尔比12：1，反应时间9h。催化剂经简单处理后．可重复使用4次且催化活性没有明显降低。所得生物柴油品质良好，基本达到相关标准。     

漆酶在制浆造纸中的应用

漆酶是一种含铜多酚氧化酶,参与木素的降解或聚合,具有氧化木素的能力.该文主要论述了漆酶的催化氧化机理以及漆酶在制浆造纸方面的应用在纸浆生物漂白、生物制浆和机械浆预处理、废纸脱墨、纸浆增湿强作用和处理制浆废水方面等.     

微生物胺氧化酶研究进展

胺氧化酶是一类有特殊生物功能的蛋白质,它能将生物胺降解为乙醛、氨、过氧化氢,从而可以减缓生物胺在食品中的危害。该文主要针对微生物所产的胺氧化酶的分类进行综述,根据辅助因子的不同将其分为含铜胺氧化酶和含黄素胺氧化酶,并从食品质量安全角度出发介绍了胺氧化酶在食品领域中的应用,最后展望了微生物胺氧化酶研究的前景。对微生物胺氧化酶种类的了解提供了依据,并对胺氧化酶在食品工业中应用提供了借鉴。     

油脂加氢脱氧制备第二代生物柴油催化剂研究进展

第二代生物柴油作为一种重要的石化柴油替代燃料,具有较好的应用前景,催化剂是制约其发展的重要因素。综述了油脂加氢脱氧催化剂的研究新进展,重点论述了油脂加氢脱氧制备第二代生物柴油的反应机制以及催化剂的活性组分、助剂、载体等,分析了催化剂失活的原因,并指出了今后的发展方向。贵金属基催化剂价格昂贵,导致生物柴油生产工艺的成本高,限制了其大规模的工业化生产和技术发展;过渡金属基催化剂价格便宜,但存在催化效果较差、催化剂容易失活等问题;助剂和载体也极大地影响催化剂的活性、选择性和稳定性。综上,对非贵金属基催化剂改性、添加助剂或采用改性复合载体,开发新型、高效、稳定性好的油脂加氢脱氧催化剂是今后的发展方向。     

用米糠油制取生物柴油

论述了用米糠油为原较,甲醇作酯化剂,在催化剂的作用下制取生物柴油的方法。     

烟草中多酚氧化酶的特征分析及应用展望

烟草中多酚氧化酶(PPO)介导的褐交会影响烟叶和烟丝的色泽和内在质量，因此对其特性的研究，以及活性的控制成为多年来的研究热点。笔者从PPO生物发生模型，分子结构，生物化学和光谱学特征及其与植物抗病和机械损伤的关系，多酚氧化酶的抑制，多酚氧化酶的应用等方面，对近几年来烟草中PPO研究的最新成果进行了回顾和总结，对一些有争议的问题进行了探讨，并对未来PPO研究的方向和领域进行了展望。     

生物质快速热解生物油产率和组分的影响因素

生物质快速热解是能源转化中效率较高的一种。本文从物料特性(物料组成、粒径、含水率)和反应条件(升温速率、反应温度、滞留时间、压力和催化剂)两方面对影响生物油产率和组分进行论述,分析了影响生物油组分的主要因素:物料组成、反应温度和催化剂,对影响生物油产率的主要因素物料粒径、温度和气体停留时间进行阐述。     

生物炭基固体酸催化剂制备及其催化油酸酯化性能的研究

以去除半纤维素的玉米芯为原料，通过高温炭化、浓硫酸磺化制备了生物炭基固体酸催化剂，用于油酸酯化制备生物柴油，并对催化剂进行了表征。考察了炭化温度、炭化时间、磺化温度、磺化时间等制备条件对催化剂的影响，探究了反应温度、反应时间、醇油摩尔比、催化剂质量分数对油酸酯化反应的影响。结果表明，适宜的催化剂制备条件为300 ℃炭化3 h、25 ℃磺化4 h，在此条件下制备的生物炭基固体酸酸量为1.67 mmol/L；适宜的反应条件为反应温度65 ℃，反应时间5 h，甲醇与油酸的摩尔比12：1，催化剂质量分数4%，在此条件下，油酸转化率为98%。催化剂在使用4次后，催化剂活性下降至63%，经过重新磺化，油酸转化率可恢复至94%。     

固体超强酸SO^2- 4/Fe2O3催化制备生物柴油的研究

采用沉淀-浸渍法制备固体超强酸SO^2- 4/Fe2O3催化剂，并将该催化剂用于生物柴油的制备。研究了沉淀温度、焙烧温度对催化剂性能的影响，用FTIR对催化剂进行了表征。考察了催化剂用量、醇油摩尔比、反应温度、反应时间对生物柴油收率的影响。实验表明，SO^2- 4/Fe2O3固体超强酸对制备生物柴油具有较高催化活性，冰水浴中沉淀、500℃焙烧效果最佳。SO^2- 4/Fe2O3固体超强酸催化制备生物柴油的最佳工艺条件为：催化剂用量为原料油质量的2％，醇油摩尔比12：1，反应温度220℃，反应时间8h。在最佳条件下，生物柴油收率可达80％以上。催化剂重复使用5次（40h），生物柴油收率仍在70％以上。     

酶在反胶束体系中应用

该文介绍反胶束和反胶束酶体系结构,动力学模型,并着重介绍其应用范围,并对今后反胶束应用进行展望。     

反胶束体系下酶催化反应研究进展

反胶束体系是表面活性剂在非极性溶剂中自发形成与正常胶束结构相反含水聚集体。该 文综述含酶反胶束体系的制备、结构和在反胶束体系下酶的活性、稳定性及动力学特性,介绍反胶 束体系下酶催化反应类型、优点及其应用,并展望其发展前景。     

Biosynthesis and regulation of microbial polyunsaturated fatty acid production

Growing interest in polyunsaturated fatty acid (PUFA) applications in various fields coupled with their significance in health and dietary requirements has focused attention on the provision of suitable sources of these compounds. Isolation of highly efficient oleaginous microorganisms has led to the development of fermentation technologies as an alternative to agricultural and animal processes. Particularly active in PUFA synthesis are the Zygomycetes fungi and certain microalgae. Emphasis is placed on increasing the product value by employing new biotechnological strategies (e.g. mutation techniques, molecular engineering and biotransformations) which allow the regulation of microbial PUFA formation with satisfactory yield in order to be competitive with other sources. Comparative successes in fungal PUFA production demonstrate microbial potential to synthesize high-value oils and provide the main stimulus for their applications.     

生物酶在染整加工中的应用(一)

生物酶是一种天然的大分子量蛋白质,能有效催化化学反应的进程,具有作用条件温和以及操作安全的特点,被喻为“生物催化剂”。生物酶能完全生物降解,很小的用量就能发挥突出的效能,因而已越来越多地被应用于纺织染整加工中,如酶退浆、酶精练、酶漂白和酶整理等。酶制剂作为一种生物制剂,无毒无害,它的开发应用顺应了绿色生产加工和可持续发展的要求,具有广阔的应用前景。文章以棉织物为例,介绍生物酶在染整加工中的应用。     

Oxidative degradation and non-enzymatic browning due to the interaction between oxidised lipids and primary amine groups in different marine PL emulsions

Due to the beneficial health effects of marine phospholipids (PL) there is an increasing industrial interest in using them for nutritional applications including emulsified foods. This study was undertaken to investigate both oxidative and hydrolytic stability of marine PL emulsions in relation to the chemical composition of the marine PL used. Moreover, non-enzymatic browning reactions were also investigated. Emulsions were prepared by high pressure homogenizer using different concentrations and sources of marine PL. In some formulations, fish oil was added in order to study the effect of increasing levels of triglycerides in the emulsions. The oxidative and hydrolytic stability of emulsions was investigated through measurement of peroxide value, free fatty acids, and ³¹P NMR during storage at 2 °C for up to 32 days. The oxidative stability of marine PL emulsions during storage was further investigated through the measurement of secondary volatile compounds by solid-phase microextraction (SPME) and dynamic headspace (DHS) connected to gas chromatography (GC–MS). Non-enzymatic browning reactions were investigated through the measurement of Strecker derived volatiles, colour changes and pyrrole content. The results suggested that the oxidative stability of marine PL emulsions was significantly influenced by the chemical composition and the concentration of marine PL used to prepare them. Emulsions with good oxidative stability could be prepared from marine PL of high purity and high content of PL and antioxidant and low TAG content.     

Activated oxygen species and oxidation of food constituents.

Activated oxygen species which may be important in initiating oxidative changes in foods include singlet oxygen, hydroxyl radical, ozone, superoxide anion (perhydroxyl radical at low pH), and hydrogen peroxide. Chemical and enzymic reactions known to occur in biological materials can generate singlet oxygen, hydroxyl radical, superoxide anion, and hydrogen peroxide. Ozone is primarily a product of photoreactions in polluted air. Reactions involving singlet oxygen, hydroxyl radical, and ozone with food constituents can ultimately yield peroxides which decompose to initiate oxidative chain reactions. Superoxide anion and hydrogen peroxide are relatively inert toward organic molecules but can decompose to produce the more reactive singlet oxygen and hydroxyl radical. Inhibition of reactions initiated by reactive oxygen species in foods should be very important in preserving the oxidative stability of foods. The generation, detection, measurement, reaction, and inhibition of reactions of active oxygen species are surveyed in this review.     

Activated oxygen species and oxidation of food constituents

Activated oxygen species which may be important in initiating oxidative changes in foods include singlet oxygen, hydroxyl radical, ozone, superoxide anion (perhydroxyl radical at low pH), and hydrogen peroxide. Chemical and enzymic reactions known to occur in biological materials can generate singlet oxygen, hydroxyl radical, superoxide anion, and hydrogen peroxide. Ozone is primarily a product of photoreactions in polluted air. Reactions involving singlet oxygen, hydroxyl radical, and ozone with food constituents can ultimately yield peroxides which decompose to initiate oxidative chain reactions. Superoxide anion and hydrogen peroxide are relatively inert toward organic molecules but can decompose to produce the more reactive singlet oxygen and hydroxyl radical. Inhibition of reactions initiated by reactive oxygen species in foods should be very important in preserving the oxidative stability of foods. The generation, detection, measurement, reaction, and inhibition of reactions of active oxygen species are surveyed in this review.     

DPPH Radical Scavenging and Allelopathic Activities of 6-Hydroxyharman Obtained from an Improved Biotransformation of Harman by Cunninghamella Blakesleeana

Continuing our work of using biotransformations reactions to produce hydroxylated compounds at inaccessible positions, 6-hydroxyharman was obtained from hydroxylation of harman by Cunninghamella blakesleeana. The yield of this biohydroxylation was seven times higher in the presence of the surfactant PEG-400. Both, reagent and product, had their activities evaluated in the 2,2-diphenyl-1-picrylhydrazyl radical scavenging capacity assay and in the allelopathic bioassay on radical and shoot growth of L. sativa (lettuce). 6-Hydroxyharman showed, in the first assay, very high radical scavenger activity, contrasting with harman, that was inactive. In the allelopathic bioassay, 6-hydroxyharman presented more inhibitory and stimulatory effect than harman, in analogous concentrations.     

Lipid and protein oxidation and sensory properties of vacuum-packaged dry-cured ham subjected to high hydrostatic pressure

The effect of HHP treatment (600 MPa) on the oxidative stability of lipids and proteins of vacuum-packaged Iberian dry-cured ham and the impact on the sensory characteristics of the product was investigated. In order to assess how different commercial presentations are affected by HHP treatment, three different presentations of vacuum-packaged Iberian dry-cured ham were considered, namely, (i) intact format (IF) corresponding to non-sliced vacuum-packaged dry-cured ham, (ii) conventional-sliced format (CSF) corresponding to dry-cured ham slices placed stretched out in the package and (iii) alternative-sliced format (ASF) corresponding to dry-cured ham slices piled up horizontally. The oxidation of dry-cured ham lipids and proteins was enhanced by HHP-treatment with the presentation being highly influential on these oxidative reactions. Pre-slicing dry-cured ham results in a more susceptible product to oxidative reactions during pressurisation and subsequent refrigerated storage. Possible mechanisms, by which HHP-induced oxidative reactions would affect particular sensory traits in vacuum-packaged Iberian dry-cured ham such as colour, texture and flavour attributes, are discussed.     

Transformation and removal of bisphenol A from aqueous phase via peroxidase mediated oxidative coupling reactions: efficacy, products, and pathways

A systematic investigation of the feasibility of and mechanisms for transformation and removal of bisphenol A (BPA) from aqueous phase via oxidative coupling mediated by horseradish peroxidase is described. It is demonstrated that BPA can be effectively transformed into precipitable solid products in HRP-mediated oxidative coupling reactions. A total of 13 reaction intermediates and products are identified using LC/MS and GC/MS techniques, and with the help of ab initio molecular modeling, detailed reaction pathways are proposed. It is postulated that two BPA radicals are coupled primarily by the interaction of an oxygen atom on one radical and propyl-substituted aromatic carbon atom on another, followed by elimination of an isopropylphenol carboncation. All intermediates or products detected can be interpreted as resulting from either coupling or substitution reactions between BPA and other intermediates or products. The efficacy of the reaction at low substrate concentrations is demonstrated using a sensitive analytical procedure involving solid-phase extractions. The results suggest that catalyzed oxidative coupling reactions may be important natural transformation pathways for estrogenic phenolic compounds and indicate their potential use as an efficient means for removal of estrogenicity from waters and wastewaters.