活性污泥合成PHAs单体组分的调控方法

聚羟基烷酸酯（PHAs）是一类生物合成的环境友好高分子塑料，具有广泛应用前景。活性污泥合成PHAs可降低PHAs生产成本，实现废物资源化。PHAs的物化性质取决于其单体组分的结构和含量。基于优化PHAs产量的工艺研究，总结了调控活性污泥合成的聚羟基丁酸 羟基戊酸（PHBV）中羟基戊酰含量的工艺措施和生化原理。已有研究表明，好氧时，碳源类型决定PHBV中的单体组分;一般地，溶解氧浓度（DO）降低，PHBV中HV含量会增加;污泥来源、pH值以及碳源与氮磷浓度比的变化都会影响HV含量;各参数对PHAs组分的影响存在关联性。展望了调控活性污泥合成PHAs中单体组分的进一步研究方向。     

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。     

可生物降解塑料聚-β=羟基丁酸酯（PHB）

聚羟基链烷酯(Polyhydroxyalkanoate，PHAs)是一类微生物聚酯的简称，由于PHAs不仅具有化学合成塑料的特性，还具有一些特殊性能，如生物可降解性、生物相容性、光学活性以及在生物合成过程中可利用再生原料等，因而在医学、农业、电子和食品等工业领域具有广阔的应用前景，可望成为一种替代传统塑料的新型高分子材料，为解决“白色污染”带来希望。目前已鉴定的PHAs约有40种，其中PHB是PHAs的典型代表。它存在于多种微生物中，具有广泛的应用前景。     

生物基热固性树脂研究获系列进展

<正>随着人们对生物基高分子材料研究的日益广泛和深入,生物基热固性树脂作为生物基高分子材料的一个重要品类也逐步为大家所接受和重视。但是,如何通过生物基平台化合物的选择、分子结构设计和调控实现其高性能化、功能化和适用化一直是一个难点问题。中国科学院宁波材料技术与工程研究所生物基高分子材料研究团队在国内率先布局和开展了生物基热固性树脂的研究方向,近几年来,在基于     

纤维的超分子结构与力学性质

<正> 众所周知,材料的性能取决于结构,换言之,结构是内在本质,性能则是外部现象。对高分子材料而言,超分子结构(即分子聚集态)对物理机械性能具有决定性的影响,因此,研究纤维的超分子结构对于研究新品种纤维或纤维改性有着重要意义。人们为阐明高聚物结构和性能之间的关系,曾做了大量的工作,所谓“高分子设计’就是这些工作进展的反映。现代化测试仪器的发展又为纤维结构的研究提供了有利条件。     

高分子科学 名词解释

正自增强高分子[self-reinforcing polymer]能以大分子结构或超分子结构的尺度形成增强体的高分子材料。由于它与基体的化学结构完全相同,则称这种增强方式为分子自增强。目前高分子自增强材料有两类:(1)采用棒状刚性链构造而成的自增强材料,其典型代表是主链液晶高分子;(2)     

意可曼投建完全可降解生物材料项目投产

<正>中国山东消息,山东省邹城市一大型可完全生物降解材料项目将于近期投入运营。该项目由深圳意可曼生物科技有限公司投资,专门从事可完全生物降解高分子材料聚羟基烷酸(PHAs)产品的研发、生产     

活性污泥合成聚羟基烷酸酯中单体组分的调控

聚羟基烷酸酯(PHAs)是一类生物合成的环境友好高分子塑料,具有广泛应用前景.活性污泥合成PHAs可降低PHAs生产成本,实现废物资源化.PHAs的物化性质取决于其单体组分的结构和含量.基于优化PHAs产量的工艺研究,总结了调控活性污泥合成的聚羟基丁酸-羟基戊酸(PHBV)中羟基戊酰含量的工艺措施和生化原理.已有研究表明,好氧时,碳源类型决定PHBV中的单体组分;一般地,溶解氧浓度(DO)降低,PHBV中HV含量会增加;污泥来源、pH值以及碳源与氮磷浓度比的变化都会影响HV含量;各参数对PHAs组分的影响存在关联性.展望了调控活性污泥合成PHAs中单体组分的进一步研究方向.     

液晶高分子的分子设计

简单介绍了液晶高分子的结构特点，分类及其应用状况，详细介绍了主链型和侧链型液晶高分子设计的新进展，根据溶臻主链型液晶高分子和热臻主链型液晶高分子分子结构的不同，提出今后设计主链液晶高分子的主要任务，从主链结构，液晶基元类型和柔性间隔出发介绍了侧链液晶高分子分子设计的关键，最后介绍了液晶高分子分子设计的发展趋势。     

高分子设计

高分子设计焦书科（北京化工大学高分子材料系，１０００２９）１高分子设计学科的建立与发展高分子设计的全称是高相对分子质量化合物（聚合物）的分子设计，广义上它也包括以聚合物作基料的高分子材料的分子设计。高分子材料的性能是由复杂的物料、结构体系和加工技术所...     

Polyhydroxyalkanoates: Recent Advances in Their Synthesis and Applications

Polyhydroxyalkanoates (PHAs) are microbial biopolymers (polyesters) that have a wide range of functions and applications. They serve in nature mainly as carbon and energy storage materials for a variety of microorganisms. In past decades, their utilization has attracted much attention, from commodities and degradable plastics to specialty performance materials in medicine. PHA biosynthesis has been well understood, and it is now possible to design bacterial strands to produce PHAs with desired properties. The substrates for the fermentative production of PHAs are very manifold: some are derived from food‐based carbon sources (e.g., fats and oils (triglycerids)), thus raising concerns with regard to the sustainability of their productions in terms of crop area and food. In addition, hemicellulose hydrolysates, crude glycerol, and methanol are very promising carbon sources for the sustainable production of PHAs. The integration of PHA production within a modern biorefinery is an important issue and can result in a simultaneous production of biofuels and bioplastics. Furthermore, many chemical‐synthetic procedures by means of efficient catalysts can give access to a variety of PHAs. This article summarizes recent developments in these fields and emphasizes the importance of a sustainable PHA‐based industry. Practical Applications: Practical applications of the microbial polyesters PHAs are, for example, a variety of sustainably produced commodities as well as special applications in (bio)medicine, for example, tissue engineering.     

Polyhydroxyalkanoates,a family of natural polymers,and their applications in drug delivery

Polyhydroxyalkanoates (PHAs) are natural biopolymers produced by various microorganisms as a reserve of carbon and energy. PHA synthesis generally occurs during fermentation under nutrient limiting conditions with excess carbon. There are two main types of PHAs, short chain length PHAs (scl‐PHAs) and medium chain length PHAs (mcl‐PHAs). The mechanical and thermal properties of PHAs depend mainly on the number of carbons in the monomer unit and its molecular weight. PHAs are promising materials for biomedical applications because they are biodegradable, non‐toxic and biocompatible. The large range of PHAs, along with their varying physical properties and high biocompatibility, make them highly attractive biomaterials for use in drug delivery. They can be used to produce tablets, micro‐ and nanoparticles as well as drug eluting scaffolds. A large range of different PHAs have been explored and the results obtained suggest that PHAs are excellent candidates for controlled and targeted drug delivery systems. © 2015 Society of Chemical Industry     

Integrated Biorefinery Design with Techno-Economic and Life Cycle Assessment Tools in Polyhydroxyalkanoates Processing

To support and move toward a sustainable bioeconomy, the production of polyhydroxyalkanoates (PHAs) using renewable biomass has acquired more attention. However, expensive biomass pretreatment and low yield of PHAs pose significant disadvantages in its large-scale production. To overcome such limitations, the most recent advances in metabolic engineering strategies used to develop high-performance strains that are leading to a new manufacturing concept converting biomass to PHAs with co-products such as amino acids, proteins, biohydrogen, biosurfactants, and various fine chemicals are critically summarized. This review article presents a comprehensive roadmap that highlights the integrated biorefinery strategies, lifecycle analysis, and techno-economic assessment for sustainable and economic PHAs production. Finally, current and future challenges that must be addressed to transfer this technology to real-world applications are reviewed.     

动胶菌发酵生产聚羟基烷酸的动力学模型

引言 聚羟基烷酸(PHAs)是许多细菌细胞内积累的一种碳源和能源贮藏物质[1-2],仅由C、H和O元素组成[3],是一类可完全生物降解、具有良好加工性能和广阔应用前景的新型热塑性材料[4-6].为实现PHAs发酵的优化控制,必须对发酵过程的菌体生长和产物形成的动力学有充分的研究和了解,以降低生产成本,为最终实现工业化生产打下基础.因此,动力学模型的建立,对优化控制发酵条件,实现规模生产是必不可少的.目前,国内外的研究主要集中利用Wautersia eutropha及工程菌株生产PHAs,关于以Wautersia eutropha生产PHB的发酵动力学模型报道很多[7-9],但是由于Wautersia eutropha产PHAs的培养条件较为严格,对微量元素和碳氮源浓度都有要求[9],故此生产成本较高.     

Lignocellulosic and marine biomass as resource for production of polyhydroxyalkanoates

Polyhydroxyalkanoates (PHAs) are considered as sustainable ‘green/bio plastics’ because they have potential to replace their depleting petroleum-based competitors in the recent future. To reach this goal, PHAs must be able to compete with the established petroleum-based plastics in both technical and economic aspects. The current PHA production is based on high-priced substrates of high nutritional value and simple carbon sources such as glucose, sucrose, starch, or vegetable oils. Non-food based carbon-rich complex polysaccharides of lignocellulosic and marine biomass can be used as alternative and suitable feedstock through consolidated bioprocessing (CBP). CBP is a promising strategy that involves the production of lytic enzymes, hydrolysis of biomass, and fermentation of resulting sugars to desired products in a single process step. CBP offers very large cost reductions if microorganisms possessing the abilities are found or microbial processes are developed to utilize substrate and simultaneously produce products. This review focuses on possible available complex polysaccharides of lignocellulosic and marine biomass that can be used as resources to produce PHAs in biorefineries, including CBP.     

Production of polyhydroxyalkanoates: the future green materials of choice

Polyhydroxyalkanoates (PHAs) have recently been the focus of attention as a biodegradable and biocompatible substitute for conventional non degradable plastics. The cost of large‐scale production of these polymers has inhibited its widespread use. Thus, economical, large‐scale production of PHAs is currently being studied intensively. Various bacterial strains, either wild‐type or recombinant have been utilized with a wide spectrum of utilizable carbon sources. New fermentation strategies have been developed for the efficient production of PHAs at high concentration and productivity. With the current advances, PHAs can now be produced to a concentration of 80 g L^?1 with productivities greater than 4 g PHA L^?1 h^?1. These advances will further lower the production cost of PHAs and allow this family of polymers to become a leading biodegradable polymer in the near future. This review describes the properties of PHAs, their uses, the various attempts towards the production of PHAs, focusing on the utilization of cheap substrates and the development of different fermentation strategies for the production of these polymers, an essential step forward towards their widespread use. Copyright © 2010 Society of Chemical Industry     

RETRACTED ARTICLE: Towards understanding polyhydroxyalkanoates and their use

It is fact that Polymers and their products have changed the face of the world in all the field of the technology. They are the future of the coming up generation of the research of the world. But this is also fact that these synthetic non biodegradable polymers have created a tough situation for the living being for a healthy life. Polyhydroxyalkanoates are polyesters produced by bacteria as intracellular storage materials in response to a variety of nutritional and environmental conditions, such as nitrogen limitation Polyhydroxyalkanoates (PHAs) are gaining increasing attention in the biodegradable polymer market due to their promising properties such as high biodegradability in different environments, not just in composting plants, and processing versatility. Indeed among biopolymers, these biogenic polyesters represent a potential sustainable replacement for fossil fuel-based thermoplastics. Most commercially available PHAs are obtained with pure microbial cultures grown on renewable feedstocks (i.e.glucose) under sterile conditions but recent research studies focus on the use of wastes as growth media.PHA can be extracted from the bacteria cell and then formulated and processed by extrusion for production of rigid and flexible plastic suitable not just for the most assessed medical applications but also considered for applications including packaging, moulded goods, paper coatings, non-oven fabrics, adhesives, films and performance additives. The present paper reviews the PHAs, their main properties, processing aspects, commercially available ones, as well as limitations and related improvements being researched,with specific focus on potential applications of PHAs in packaging.     

Storage of biodegradable polymers by an enriched microbial community in a sequencing batch reactor operated at high organic load rate

The production of polyhydroxyalkanoates (PHAs) from organic acids by mixed bacterial cultures using a process based on aerobic enrichment of activated sludge, that selects for mixed microbial cultures able to store PHAs at high rates and yields, is described. Enrichment resulted from the selective pressure established by periodic feeding the carbon source in a sequencing batch reactor (SBR); a mixture of acetic, lactic and propionic acids was fed at high frequency (2 hourly), high dilution rate (1 d⁻¹), and at high organic load rate (12.75 g chemical oxygen demand (COD) L⁻¹ d⁻¹). The performance of the SBR was assessed by microbial biomass and PHA production as well as the composition and polymer content of the biomass. A final batch stage was used to increase the polymer concentration of the excess sludge produced in the SBR and in which the behaviour of the biomass was investigated by determining PHA production rates and yields. The microbial biomass selected in the SBR produced PHAs at high rate [278 mg PHAs (as COD) g biomass (as COD)⁻¹ h⁻¹, with a yield of 0.39 mg PHAs (as COD) mg removed substrates (as COD)⁻¹], reaching a polymer content higher than 50% (on a COD basis). The stored polymer was the copolymer poly(3‐hydroxybutyrate/3‐hydroxyvalerate) [P(HB/HV)], with an HV fraction of 18% mol mol⁻¹. The microbial community selected in the SBR was analysed by DGGE (denaturing gradient gel electrophoresis). The operating conditions of the SBR were shown to select for a restricted microbial population which appeared quite different in terms of composition with respect to the initial microbial cenosis in the activated sludge used as inoculum. On the basis of the sequencing of the major bands in the DGGE profiles, four main genera were identified: a Methylobacteriaceae bacterium, Flavobacterium sp, Candidatus Meganema perideroedes, and Thauera sp. The effects of nitrogen depletion (ie absence of growth) and pH variation were also investigated in the batch stage and compared with the SBR operative mode. Absence of growth did not stimulate higher PHA production, so indicating that the periodic feed regime fully exploited the storage potential of the enriched culture. Polymer production rates remained high between pH 6.5 and 9.5, whereas the HV content in the stored polymer strongly increased as the pH value increased. This study shows that polymer composition in the final batch stage can readily be controlled independently from the feed composition in the SBR. Copyright © 2005 Society of Chemical Industry     

Chemical characterization of medium‐chain‐length polyhydroxyalkanoates (PHAs) recovered by enzymatic treatment and ultrafiltration

BACKGROUND: Medium‐chain‐length polyhydroxyalkanoates (PHAs) are biodegradable polyesters accumulated intracellularly as energy resources by bacterial species such as Pseudomonas putida. The most popular method for PHA recovery is solvent extraction using trichloromethane (chloroform) and methyl alcohol (methanol). An alternative method is enzymatic treatment, which eliminates usage of these hazardous solvents. This research focuses on the characterization of PHAs recovered by enzymatic treatments and ultrafiltration. Comparisons are made with conventional solvent extracted PHA. RESULTS: The purity of PHA in water suspension recovered by enzymatic treatments as analyzed by gas chromatography was 92.6%. Enzymatically recovered PHA was comparable to conventional solvent‐extracted PHA, which had a purity of 95.5%. PHA was further characterized for functional group analysis, structural composition analysis and molecular weight determination. It was found that the molecular weight of the PHA recovered by enzymatic treatment was less than solvent‐extracted PHA, probably due to degradation of the lipopolysaccharide layer. However, functional group and structural composition analyses showed similar results for PHA recovered by both methods. CONCLUSION: PHAs recovered through enzymatic digestion treatment have good comparability with solvent‐extracted PHAs. Thus enzymatic digestion has great potential as an alternative recovery method. Copyright © 2007 Society of Chemical Industry