新型生物材料PHAs用于污水固相脱氮处理

介绍了生物可降解聚合体PHAs（聚羟基脂肪酸酯）的特点及其在污水反硝化脱氯中的应用。与传统液相有机基质脱氮相比，PHAs固相基质脱氮具有很多优点：为脱氮过程提供了连续的资源；有利于生物膜的培养和生成；PHAs释放的不溶有机碳不会对水质产生潜在的危害。PHAs固相基质脱氮技术已显现出了良好的应用前景。     

Extruded Biodegradable Cast Films from Polyhydroxyalkanoate and Thermoplastic Starch Blends: Fabrication and Characterization

PHA‐based extruded films were developed by blending PHAs with thermoplastic starch using extensive process engineering based on structure‐property correlations. Starch was destructurized and plasticized followed by melt‐blending with PHA and PBAT. Dynamic mechanical analysis coupled with Gibbs free energy values indicated that the starch plastic was performing the role of a dual compatibilizer in between the PHA and the PBAT phases in the blend. Aging, an inherent problem with starch‐based materials and PHA‐based materials, was effectively reduced by limiting the moisture uptake of the starch component, hindering the leaching of glycerol and inhibiting the secondary crystallization of the PHA component in the films.

     

嗜盐微生物底盘细胞：应用和前景

嗜盐微生物是一种耐高盐的微生物,有细菌、古菌、藻类等。其中的中度嗜盐菌耐受30~150g/L的氯化钠,有很高的研究价值和应用前景。嗜盐微生物可以在海水中生长,有的同时嗜碱,尤其不少嗜盐细菌在矿物培养基中生长迅速,具有作为底盘细胞的优势。随着近年来对嗜盐微生物分子操作工具的不断开发,嗜盐细菌的改造工作得到了迅猛发展。工程化的嗜盐微生物已经可以用于合成数种聚羟基脂肪酸酯（PHA）,也用于大规模生产多种聚合物、蛋白质、小分子化合物、氨基酸和化妆品原料。合成生物学技术的使用也使嗜盐微生物实现了可控形变, 有利于更多的胞内产物的合成和下游的细胞分离。根据嗜盐微生物,特别是嗜盐细菌的特点和研究进展,本文提出了以嗜盐微生物作为底盘细胞的“下一代工业生物技术”,使发酵工业实现开放式的节能、节水、连续、全自动的过程,减少微生物大规模培养的复杂程度和对设备的高要求,同时能联产生产多种产品,大幅度降低工业生物技术的制造成本,提高产品的竞争性。     

嗜水气单胞菌胞内聚3-羟基丁酸-3-羟基己酸酯（PHBHHx）提取方法的研究

以嗜水气单胞菌利用月桂酸发酵生产PHBHHx,比较多种溶剂对提取率和产品质量的影响,建立了嗜水气单胞菌胞内提取PHBHHx的新方法。本方法使用湿细胞提取,节省干燥细胞的能耗,仲丁醇无异味、毒性小、价格低廉,而且可以循环多次利用、对相对分子质量影响小,解决了工业生产上能耗高,生产成本高,溶剂回收难,安全隐患多,提取率不高、产品质量低等问题。用仲丁醇作溶剂,预处理细胞提取率提高13％,相对分子质量达83万,提取率达78％,产品纯度达99％以上。     

Production and characterization of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) co‐polymer by a N2‐fixing cyanobacterium,Nostoc muscorum Agardh

BACKGROUND: Poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) [P(3HB‐co‐3HV)] co‐polymer has immense potential in the field of environmental and biomedical sciences as biodegradable and biocompatible material. The present study examines a filamentous N₂‐fixing cyanobacterium, Nostoc muscorum Agardh as a potent feedstock for P(3HB‐co‐3HV) co‐polymer production and characterization of co‐polymer film for commercial applications. RESULTS: Under photoautotrophic growth conditions, N. muscorum Agardh accumulated the homopolymer of poly‐β‐hydroxybutyrate (PHB), whereas synthesis of P(3HB‐co‐3HV) co‐polymer was detected under propionate‐ and valerate‐supplemented conditions. Exogenous carbons such as acetate, fructose and glucose supplementation with propionate/valerate was found highly stimulatory for the co‐polymer accumulation; the content reached 58–60% of dry cell weight (dcw) under P‐/N‐deficiencies with 0.4% acetate + 0.4% valerate supplementation, the highest value reported so far for P(3HB‐co‐3HV) co‐polymer‐producing cyanobacterial species. The material properties of the films were studied by mechanical tests, surface analysis and differential scanning calorimetry (DSC). CONCLUSION: N. muscorum Agardh, a photoautotrophic N₂‐fixing cyanobacterium, emerged as a potent host for production of P(3HB‐co‐3HV) co‐polymer with polymer content 60% of dry cell weight. The material properties of the films were found to be comparable with that of the commercial polymer, thus advocating its potential applications in various fields. Copyright © 2012 Society of Chemical Industry     

厌氧HRT对A/O除磷工艺的影响

为系统考察厌氧水力停留时间（AHRT）对生物除磷效果的影响,本文以实际生活污水作为进水,在实验室连续流厌氧／好氧（A／O）除磷系统稳定运行的基础上,统计了不同AHRT下系统除磷效果及胞内贮存物的变化。设计批式实验,考察了AHRT较长情况下生物增强除磷代谢过程,针对实验过程中出现的厌氧聚羟基链烷酸酯（PHAs）分解和厌氧糖原合成现象,提出聚磷不足情况下聚磷菌代谢的假想模式。最后根据实验结果指出A／O除磷工艺AHRT的确定应以PHAs的合成量最大作为控制目标。     

Vimentin Cytoskeleton Architecture Analysis on Polylactide and Polyhydroxyoctanoate Substrates for Cell Culturing

Polylactide (PLA), widely used in bioengineering and medicine, gained popularity due to its biocompatibility and biodegradability. Natural origin and eco-friendly background encourage the search of novel materials with such features, such as polyhydroxyoctanoate (P(3HO)), a polyester of bacterial origin. Physicochemical features of both P(3HO) and PLA have an impact on cellular response 32, i.e., adhesion, migration, and cell morphology, based on the signaling and changes in the architecture of the three cytoskeletal networks: microfilaments (F-actin), microtubules, and intermediate filaments (IF). To investigate the role of IF in the cellular response to the substrate, we focused on vimentin intermediate filaments (VIFs), present in mouse embryonic fibroblast cells (MEF). VIFs maintain cell integrity and protect it from external mechanical stress, and also take part in the transmission of signals from the exterior of the cell to its inner organelles, which is under constant investigation. Physiochemical properties of a substrate have an impact on cells’ morphology, and thus on cytoskeleton network signaling and assembly. In this work, we show how PLA and P(3HO) crystallinity and hydrophilicity influence VIFs, and we identify that two different types of vimentin cytoskeleton architecture: network “classic” and “nutshell-like” are expressed by MEFs in different numbers of cells depending on substrate features.     

Metabolic improvements and use of inexpensive carbon sources in microbial production of polyhydroxyalkanoates

This paper deals with the microbial production of polyhydroxyalkanoates (PHAs), biodegradable thermoplastics which perform excellently as a material, from inexpensive renewable carbon sources. To date, with the help of genetic engineering techniques, it has become possible to design several types of PHAs with different compositions and to enhance the productivities of PHAs. In addition, molecular breeding of PHA biosynthesis enzymes has been demonstrated to improve polymer production. Mutant PHA synthases generated by an in vitro evolution technique have allowed the enhanced production and quality alteration of PHAs. Furthermore, use of inexpensive renewable carbon sources, such as plant oils, waste materials, and carbon dioxide, would be a key for a reduction in PHA production cost.     

聚羟基烷酸酯的研究进展

微生物发酵合成的聚羟基烷酸酯(PHAs)作为最具有发展潜力的新型生物高分子材料之一,备受关注。本文介绍了近几年来有关PHAs的生物合成、分离纯化、性能改进、生产与应用现状等方面研究的最新进展,探讨了这一领域未来可能的发展热点和动向。     

聚羟基烷酸酯降解包装材料的生物合成及进展

目的综述聚羟基烷酸酯(Polyhydroxyalkanoates,PHAs)的生物合成工艺、影响因素及其在包装工业领域的应用研究进展,以期优化其生产工艺、降低生产成本、提高PHAs的产量。方法通过对近年来国内外研究现状和研究成果的分析和总结,介绍PHAs的生物合成工艺、影响PHAs产量的主要因素及在包装方面的应用。结论好氧瞬时供料法合成的PHAs产量高于微好氧-好氧工艺;底物种类、C/N值、pH值、溶解氧浓度和合成温度对生物合成PHAs的产量和成分比例都有很大影响;PHAs作为可降解材料在包装领域具有广阔的应用前景,未来的重点研究方向是优化PHAs的合成工艺和影响因素,降低其生产成本,提高产量和产品性能。