微生物合成PHA的研究进展

传统化石来源的塑料虽然给人类的生活带来了许多便利,但这些难降解塑料不断地堆积在环境中,导致了全球环境恶化、固体垃圾难处理等问题。因此,可生物降解塑料的研究与开发成为了近年来研究的重点。聚羟基脂肪酸酯(PHA)是一类微生物合成的高分子生物聚脂,具有良好的生物可降解性、生物相容性等特殊性质,可替代传统化石塑料成为新型生物材料,有很好的环境效应与应用前景,目前其作为心脏瓣膜材料的研究在动物实验中已取得了很好的结果。在本文中,作者结合国内外合成PHA的相关研究,对合成PHA微生物的种类及其发酵工艺进行了总结,并对其未来发展进行了展望。     

聚羟基脂肪酸酯生物合成的研究进展

聚羟基脂肪酸酯 (PHA)是原核微生物在碳、氮营养失衡的情况下 ,作为碳源和能源贮存而合成的一类热塑性聚酯。它除了具有与化学合成高分子相似的性质外 ,还具有一般化学合成高分子没有的性质 ,如生物可降解性、生物相容性、压电性、光学活性等特殊性质 ,因而具有广阔的应用前景。国内外已对PHA进行了大量的研究。本文主要综述了近二、三年来国内外对PHA生物合成的研究进展     

用活性污泥生物合成聚羟基烷酸酯的结构表征

聚β-羟基烷酸酯 ( PHA)是一类具有生物相容性、光学活性、热塑性和完全生物降解性的生物高分子 ,有巨大的应用前景 [1] .PHA的结构通式为 O CRH CH2 CO ,R为不同链长的饱和或不饱和的烷基 ,可通过微生物发酵进行合成 [2 ,3] .利用污水中的有机物和活性污泥中可积累 PHA的混合微生物群生物合成 PHA,能大大降低 PHA的成本 ,变废为宝 ,是近几年 PHA研究的新热点 [4 ,5] .用不同菌种和不同碳源合成的 PHA的结构有较大的差异 ,因污水成分复杂 ,所得 PHA是多种饱和与非饱和羟基烷酸酯的混杂共聚物 .本工作以某纺织厂活性污泥为混…     

从污水微生物合成聚羟基烷酸酯

聚羟基烷酸酯(PHA)是一类具有生物相容性、光学活性、热塑性和完全生物降解性等的生物高分子,具有巨大的应用前景.PHA是一些微生物在不平衡生长条件下胞内能量和碳源储藏物质,可通过微生物发酵合成[1,2].目前大幅度降低PHA的成本一直是国内外研究者关注的难题.通常处理有机废水的活性污泥中含有多种可积累PHA的天然微生物[3],故可以利用污水中的有机物和混合菌种群合成PHA,降低PHA的成本[4,5].本工作以某纺织厂的工业废水和城市生活污水为原料,采用微嗜气-好气过程驯化活性污泥,研究了供氧量、碳源调节物浓度、培养时间、温度等因素…     

我国聚羟基脂肪酸酯产业链的发展概况

聚羟基脂肪酸酯(PHA)是一类微生物合成的结构多样的高分子生物聚酯,具有生物可再生性、生物可降解性和良好的生物相容性,应用前景广阔.本文从PHA的材料学性质、发酵生产、提取工艺、应用前景以及我国PHA产业现状等多个方面,综述了基于PHA的产业链的相关生产和研究进展.     

聚琥珀酸丁二酯的辐射交联及其生物降解性

对聚琥珀酸丁二酯（PBS1）采用两步法辐照，比其它辐照法得到的凝胶含量高，这是由于在室温下预先辐射所形成的交联网络结构减少了聚合物的降解。交联后的PBS1有较高的耐热变形性。通过酶降解试验和土需求量法降解实验，PBS1有很高的生物降解性，即使它产生了很高的交联结构。在65℃时，酶的降解率最高。由于交联样品所含有的交联网络结构阻碍它的降解，交联PBS1的生物降解失重低于未交联样品。     

利用微生物直接生产羟基丁酸单体

利用重组大肠杆菌E.coli HB101来进行直接生产羟基丁酸(HB)手性单体,研究了含pUCAB质粒的重组体E.coli HB101在各种条件下生长及积累HB单体的情况,研究了HB单体的积累随pH值变化的规律。结果表明,pH=6.8时,48 h内细菌可生产0.5 g/L以上的HB单体。     

聚羧基脂肪酸酯细菌合成的生长环境依赖性

聚羟基脂肪酸酯（Ｐｏｌｙｈｙｄｒｏｘｙａｌｋａｎｏａｔｅ,ＰＨＡ）是一类由许多细菌合成的、结构多变的能量和碳源的储藏物质,为了得到能合成新型ＰＨＡ的菌种,或得到能在便宜简单碳源上合成ＰＨＡ的菌种,以我们实验室开发的傅立叶红外（ＦＴ－ＩＲ）细胞无损检测技术和常规气相色谱（ＧＣ）法对全国各地的采集的不同样品中分离的菌种进行了筛选,往往在不同的地理环境中,筛选出的菌株所合成的ＰＨＡ的单体组成不同,有以含四个或五个碳原子的短链单体ＰＨＡ（Ｓｈｏｒｔ－ｃｈａｉｎ－ｌｅｎｇｔｈＰＨＡ,ｓｃｌＰＨＡ）为主,有的以含六个到十六个碳原子的中长链单体ＰＨＡ（Ｍｅｄｉｕｍ－ｃｈａｉｎ－ｌｅｎｇｔｈＰＨＡ,ｍｃｌ ＰＨＡ）为主,在我们以六种底物为碳源培养的３７１株形态不一的菌株中,有４０％的菌可以合成ＰＨＡ,而其中许多可以同时合成ＰＨ     

生物可降解性聚羟基脂肪酸酯的化学合成研究进展

聚羟基脂肪酸酯是一种新型合成的脂肪族聚酯,同聚乳酸相似,具有优异的生物相容性能、生物可降解性和优良的力学机械性能,可作为生物医用材料和生物可降解包装材料,是最具前景的环境友好型聚合材料之一。目前合成聚乳酸和聚羟基脂肪酸酯的化学方法主要有开环聚合法、直接缩聚法以及自身酯交换聚合法,不过后者研究得较少。本文对这3种方法的研究进展进行了叙述,重点讨论了开环聚合法和直接缩聚法,尤其对开环聚合中的配位插入聚合的新进展进行了较详细的论述。     

生物合成聚羟基烷基酸酯的研究与开发进展

聚羟基烷基酸酯(PHA)是近20年来迅速发展起来的一种生物高分子材料,是一种具有高分子的基本性质的可热塑加工成型的聚酯.PHA最突出性能是具有优良的生物相容性和可生物降解性,因此在医学、药物、工业、农业等领域具有其独特的应用.本文综述了PHA的研究开发历史、国外发展概况、我国目前研究开发现状和国内外生物合成聚羟基烷基酸酯的研究与开发的一些最新研究成果,着重介绍了发掘具有高合成效率的新菌种、利用基因工程技术获取重组菌株、使用低成本碳源、开发合适的提取工艺等方面的工作.     

Electrospinning nanofibers of microbial polyhydroxyalkanoates for applications in medical tissue engineering

Differently to most chemically synthesized medical materials, polyhydroxyalkanoates (PHAs) are intracellular carbon and energy storage granules, which is a family of natural bio-polymers synthesized by microorganism's materials. Due to excellent biocompatibility reasonable biodegradability and versatile material difference, PHAs are well medical biomaterials candidates for applications in tissue engineering and drug delivery, including commercial PHB, PHBV, PHBHHx, PHBVHHx, P34HB and few uncommercial PHAs. Electrospinning nanofibers with the size of 10–10,000 nm can improve the mechanical properties and decrease the crystallinity of PHA, meanwhile simulate the structure and function of native extracellular matrix of cells. Hence, PHAs electrospinning nanofibers as engineered scaffolds have been widely used for tissue engineering scaffolds in cardiovascular, vascular, nerve, bone, cartilage and skin; also, as carriers for application in drug delivery system. In this review, we highlight the extraction and properties of medical PHAs from natural or engineered microorganism, and microstructure, current manufacturing techniques and medical applications of electrospinning nanofibers of PHAs. Moreover, the current challenges and prospects of PHAs electrospinning nanofibers are discussed rationally, providing an insight into developing vibrant fields of PHAs electrospinning nanofibers-based biomedicine.     

Pseudomonas stutzeri 1317合成中长链聚羟基脂肪酸酯的组成分析模型

Pseudomonasstutzeri 1317可以在不同碳源上生长,合成不同共聚单体单元组成的中长链聚羟基脂肪酸酯(mclPHAs).本文在已知的代谢途径的基础上,提出了关于mclPHAs组成的数学模型,结果表明,mclPHAs的共聚单体单元组成主要取决于前体生成途径,以及该途径和聚合途径酶对不同碳原子数前体的选择性.实验结果与文献报道结果均验证了该模型.代谢控制分析的结果表明,碳数为8～10的前体的聚合效率最高.通过调制前体生成途径,可以有效调节PHA的单体单元组成.     

Accelerated Microbial Degradation of Poly(L-lactide)

Acceleration of the biodegradation of poly(L -lactide) (PLA) was studied. We found that the degradation rate of high molecular weight (1.3×10⁵) PLA film was greatly increased by the addition of gelatin into the culture medium of the microorganisms. 100 mg of PLA film was almost completely degraded by the fungus, Tritirachium album (eukaryotic microorganisms), and by an actinomycete, Saccharothrix waywayandensis (prokaryotic microorganisms). In addition to gelatin, various insoluble proteins, peptides and amino acids also accelerate the biodegradation of PLA. Silk fibroin was the best inducer for the production of PLA-degrading enzymes of an actinomycete, Amycolatopsis orientalis.     

Biosynthesis of Polyhydroxyalkanoates (PHAs) by the Valorization of Biomass and Synthetic Waste

Synthetic pollutants are a looming threat to the entire ecosystem, including wildlife, the environment, and human health. Polyhydroxyalkanoates (PHAs) are natural biodegradable microbial polymers with a promising potential to replace synthetic plastics. This research is focused on devising a sustainable approach to produce PHAs by a new microbial strain using untreated synthetic plastics and lignocellulosic biomass. For experiments, 47 soil samples and 18 effluent samples were collected from various areas of Punjab, Pakistan. The samples were primarily screened for PHA detection on agar medium containing Nile blue A stain. The PHA positive bacterial isolates showed prominent orange–yellow fluorescence on irradiation with UV light. They were further screened for PHA estimation by submerged fermentation in the culture broth. Bacterial isolate 16a produced maximum PHA and was identified by 16S rRNA sequencing. It was identified as Stenotrophomonas maltophilia HA-16 ({"type":"entrez-nucleotide","attrs":{"text":"MN240936","term_id":"1712425297","term_text":"MN240936"}}MN240936), reported first time for PHA production. Basic fermentation parameters, such as incubation time, temperature, and pH were optimized for PHA production. Wood chips, cardboard cutouts, plastic bottle cutouts, shredded polystyrene cups, and plastic bags were optimized as alternative sustainable carbon sources for the production of PHAs. A vital finding of this study was the yield obtained by using plastic bags, i.e., 68.24 ± 0.27%. The effective use of plastic and lignocellulosic waste in the cultivation medium for the microbial production of PHA by a novel bacterial strain is discussed in the current study.     

Factorial design in optimization of PHAs processing

Poly(hydroxyalkanoate)s (PHA)s, as all melt-processed polymers, may undergo thermal degradation at temperatures close to the melting point. The primary purpose of the present study is to screen out process variables on the basis of a factorial design for two variables at two levels. The investigated parameters for PHA polymer samples processed in a torque rheometer were structure of PHA, processing temperature, and rotor speed. For polymers processed by compression molding, only the first two variables were considered and purification. The main effects and possible interactions were verified by the changes of molecular weight and thermal properties, as detected by DSC and TGA. It was observed that molecular weight decreased up to about 50% while the thermal properties did not appreciably change.     

Production of Polyhydroxyalkanoates (PHAs) by Vibrio alginolyticus Strains Isolated from Salt Fields

Vibrio alginolyticus is a halophilic organism usually found in marine environments. It has attracted attention as an opportunistic pathogen of aquatic animals and humans, but there are very few reports on polyhydroxyalkanoate (PHA) production using V. alginolyticus as the host. In this study, two V. alginolyticus strains, LHF01 and LHF02, isolated from water samples collected from salt fields were found to produce poly(3-hydroxybutyrate) (PHB) from a variety of sugars and organic acids. Glycerol was the best carbon source and yielded the highest PHB titer in both strains. Further optimization of the NaCl concentration and culture temperature improved the PHB titer from 1.87 to 5.08 g/L in V. alginolyticus LHF01. In addition, the use of propionate as a secondary carbon source resulted in the production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). V. alginolyticus LHF01 may be a promising host for PHA production using cheap waste glycerol from biodiesel refining.     

Construction of recombinant Bacillus subtilis for production of polyhydroxyalkanoates

Polyhydroxyalkanoates (PHAs) are polyesters of hydroxyalkanoates synthesized by numerous bacteria as intracellular carbon and energy storage compounds and accumulated as granules in the cytoplasm of cells. In this work, we constructed two recombinant plasmids, pBE2C1, and pBE2C1AB, containing one or two PHA synthse, genes, respectively. The two plasmids were inserted into Bacillus subtilis DB104 to generate modified strains, B. subtilis/pBE2C1 and B. subtilis/pBE2C1AB. The two recombinants strains were subjected to fermentation and showed PHA accumulation, the first reported example of mcl-PHA production in B. subtilis. Gas Chromatography analysis identified the compound produced by B. subtilis/pBE2C1 to be a hydroxydecanoate-co-hydroxydodecanoate (HD-co-HDD) polymer whereas that produced by B. subtilis/pBE2C1AB was a hydroxybutyrate-co-hydroxyde-canoate-co-hydroxydodecanoate (HB-HD-HDD) polymer.     

The oil-absorbing property of polyhydroxyalkanoate films and its practical application: a refreshing new outlook for an old degrading material

Polyhydroxyalkanoates (PHAs) have attracted the attention of academia and industry because of their plastic-like properties and biodegradability. However, practical applications as a commodity material have not materialized because of their high production cost and unsatisfactory mechanical properties. PHAs are also believed to have high-value applications as an absorbable biomaterial for tissue engineering and drug-delivery devices because of their biocompatibility. However, research in these areas is still in its very early stages. The main problem faced by proponents of PHAs is the lack of a niche area where PHAs will be the most desired material in terms of its function during use rather than because of its eco-friendly virtues after use. Here, we report on the oil-absorbing property of PHA films and its potential applications. By comparing with some of the existing commercial products, the potential application of PHAs as cosmetic oil-blotting films is revealed for the first time. Besides having the ability to rapidly absorb and retain oil, PHA films also have a natural oil-indicator property, showing obvious changes in opacity following oil absorption. Surface analysis revealed that the surface structures such as porosity and smoothness exert great influence on the rapid oil-absorption properties of the PHA films. These newly discovered properties could be exploited to create a niche area for the practical applications of PHAs.     

An expeditious synthesis of quinoxalines by using biodegradable cellulose sulfuric acid as a solid acid catalyst

A simple, efficient and environmentally friendly process for the solid state synthesis of quinoxaline derivatives by the condensation reaction of the benzo[c][1,2,5]thiadiazole-4,5-diamine and 3-(ω-bromoacetyl)-coumarins in the presence of cellulose sulfuric acid by simple physical grinding of reactants using a mortar and pestle at room temperature in good to excellent yields with high purity. The catalyst is recyclable and reusable.     

利用微生物本身的PHAs解聚酶生产羟基丁酸单体

金黄芽孢杆菌Bacillus aureus JMα5先在糖蜜上发酵积累聚羟基丁酸酯（PHB）,然后在限氧条件下降解生成手性羟基丁酸（HB）分子。研究各种培养条件如pH值、温度、时间等对该菌降解生产手性HB分子的影响。结果表明,37℃下,当pH=6时,10h内,HB单体的产量可达3．04g/L,降解率为75％,说明采用酶降解法生产HB单体具有一定的实际应用价值。在各种影响因素（包括降解体系的pH值、降解的温度和降解时间等）中,pH值对降解率的影响最大。