Environmental degradation and biofouling of ‘green’ plastics including short and medium chain length polyhydroxyalkanoates

Biopolymers derived from natural resources are potential alternatives to recalcitrant synthetic plastics; however, studies investigating the degradability of these biopolymers in natural environments are relatively few. This study compares the environmental degradation of polymers described as ‘green plastics’ in garden soil in terms of weight loss, topographical changes and biofilm attachment. Poly(3‐hydroxybutyrate) (PHB) and poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyvalerate)] (P(HB‐co‐8HV)), (copolymer containing 8 mol% HV) films degraded rapidly, losing 50% of their initial weight in 50 days. In contrast, after burial for 380 days, the medium chain length polyhydroxyoctanoate (PHO) lost 60% of its weight, poly(D ,L ‐lactide) (PDLL) 18% and poly[(D ,L ‐lactide)‐co‐glycolide] (PDLLG) 35%. Polystyrene (PS) and ethyl cellulose (EC) showed no significant degradation. Both weight loss and biofouling occurred in the following sequence: P(HB‐co‐8HV) = PHB > PHO > PDLLG > PDLL > PS = EC. The surface rugosity and surface areas of PHB and P(HB‐co‐8HV) increased three‐ and twofold, respectively, during degradation, indicating surface erosion. The surface rugosity of PHO increased twofold and the surface area increased by 25%. This in situ study demonstrates a quantifiable relationship between biofilm attachment, surface rugosity and polymer degradation. PHB and P(HB‐co‐8HV) showed greater biofouling and increased surface rugosity, and degraded significantly faster than the other polymers studied. Copyright © 2009 Society of Chemical Industry     

Quick and efficient method for genetic transformation of biopolymer‐producing bacteria

In order to genetically modify microorganisms capable of producing polyhydroxyalkanoate (PHA) biopolymers, a simple and rapid method to prepare freshly plated Pseudomonas cells for transformation via electroporation was developed. This method can be used to transfer both replicative plasmids and linear DNA to knock out genes into the cells. The transformation efficiencies were in the range of ≥10⁷ transformants µg^?1 DNA for replicative plasmids and ≥10⁶ transformants µg^?1 DNA for linear DNA, which are comparable with commercially available competent cells. Furthermore, this transformation procedure can be performed in less than 10 min, saving a great deal of time compared with traditional methods. Knockout mutants of several Pseudomonas species were generated by transformation of linear DNA and these mutations were verified by PCR and analysis of PHA content. Copyright © 2009 Society of Chemical Industry     

聚羟基脂肪酸酯成纤技术的研究进展

简述了聚羟基脂肪酸酯(PHA)的结构、结晶性能、生物降解性能及流变性能;详述了PHA及其改性聚合物静电纺丝和熔融纺丝技术的研究进展;阐述了PHA改性及纤维成形;分析指出PHA纤维成形存在的主要问题是PHA热稳定性差、结晶度高、后结晶现象严重,导致纺丝困难,纤维强度低;提出可通过添加扩链剂、增塑剂、成核剂改性PHA及使用专用油剂来提高其纺丝性能。     

一种通过重组大肠杆菌和重组恶臭假单胞菌生产3-羟基癸酸的新方法

3-hydroxydecanoic acid (3HD) is an interesting intermediate for chemical synthesis of many valuable compounds. A novel method to produce 3HD by recombinant bacteria was constructed in Escherichia coli HB101 and Pseudomonas putida GPp104, respectively. Simultaneous expression of both phaG encoding (R)-3-hydroxydecanoyl-ACP:CoA transacylase and tesB encoding thioesterase Ⅱ in E. coli HB101 increased 3HD production approximate 1.7-folds compared with the expression of phaG gene alone under identical conditions. In addition, when the tesB gene was introduced into the strain, the polyhydroxyalkanoate synthase negative strain P. putida GPpl04 produced extracellular 3HD. Thus, a novel pathway to produce 3HD by recombinant Pseudomonas was constructed. It was also found that the ratio of carbon source to nitrogen source affected the production of 3HD by recombinant P.putida harboring tesB gene. Nitrogen limitation seemed to promote the extracellular 3HD production.     

Increased sedimentation of a Pseudomonas–Saccharomyces microbial consortium producing medium chain length polyhydroxyalkanoates

Concerns about feasibility,separability,settleability,efficiency once hampered studies on polyhydroxyalkanoates(PHAs) production,which mainly focused on single strain microorganism or activated sludge rather than artificial microbial consortia.Here,a medium chain length PHAs(mcl-PHAs) producing Pseudomonas-Saccharomyces consortium with xylose as the main substrate was studied.Mcl-PHAs accumulation increased from 12.69 mg·L~(-1) to 152.3 mg·L~(-1) without any optimization method.The presence of Saccharomyces cerevisiae,though in a relatively low concentration,improved the sedimentation of cell mass of the mixed culture by 60%.Reasons for better sedimentation of the consortium were complex:first,the length of Pseudomonas putida increased two to three times in the consortium;second,the positive surface charge of P.putida was neutralized by S.cerevisiae;third,the adhesion proteins on the surface of S.cerevisiae interacted with the P.putida.     

生物降解包装材料聚羟基脂肪酸酯的工艺研究进展

目的 高昂的生产成本制约着绿色包装材料聚羟基脂肪酸酯（Polyhydroxyalkanoates, PHAs）的发展,通过对其生物合成过程中的碳源底物、影响因素的研究,实现其低成本、高效率合成以及规模化应用。方法 归纳分析现阶段国内外PHAs的研究现状和成果,介绍合成PHAs的碳源底物、微生物培养方式以及在合成阶段溶解氧（DO）、pH值、碳氮比等因素对PHAs合成效率的影响。结论 廉价的生物质资源、合理的碳氮比、多批次好氧/厌氧培养、较低的溶解氧浓度、中性或碱性培养环境已经成为提高PHAs产量、降低PHAs生产成本的重要手段。随着生产工艺的不断优化,绿色生物塑料PHAs的规模化生产及其广泛应用必将推动包装材料向绿色化、安全化方向发展。     

微生物塑料的研究现状及应用前景

综述了近几年来国内外聚羟基脂肪酸酯(PHAs)微生物合成的研究进展,同时对PHAs的应用前景进行了展望。     

Additive Manufacturing of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/Poly(D,L-lactide-co-glycolide) Biphasic Scaffolds for Bone Tissue Regeneration

Polyhydroxyalkanoates are biopolyesters whose biocompatibility, biodegradability, environmental sustainability, processing versatility, and mechanical properties make them unique scaffolding polymer candidates for tissue engineering. The development of innovative biomaterials suitable for advanced Additive Manufacturing (AM) offers new opportunities for the fabrication of customizable tissue engineering scaffolds. In particular, the blending of polymers represents a useful strategy to develop AM scaffolding materials tailored to bone tissue engineering. In this study, scaffolds from polymeric blends consisting of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly(D,L-lactide-co-glycolide) (PLGA) were fabricated employing a solution-extrusion AM technique, referred to as Computer-Aided Wet-Spinning (CAWS). The scaffold fibers were constituted by a biphasic system composed of a continuous PHBV matrix and a dispersed PLGA phase which established a microfibrillar morphology. The influence of the blend composition on the scaffold morphological, physicochemical, and biological properties was demonstrated by means of different characterization techniques. In particular, increasing the content of PLGA in the starting solution resulted in an increase in the pore size, the wettability, and the thermal stability of the scaffolds. Overall, in vitro biological experiments indicated the suitability of the scaffolds to support murine preosteoblast cell colonization and differentiation towards an osteoblastic phenotype, highlighting higher proliferation for scaffolds richer in PLGA.     

木质素生物合成可降解包装材料聚羟基脂肪酸酯的研究进展

目的 通过对木质素生物合成聚羟基脂肪酸酯(PHAs)的研究,实现PHAs的低成本、规模化生产和木质素的高值化利用。方法 归纳分析现阶段国内外木质素降解菌及生物合成PHAs的主要菌种和目前存在的问题,介绍生物合成PHAs的木质素底物种类、合成过程中工艺优化策略的相关研究进展,同时总结PHAs在包装领域的相关应用。结果 木质素生物合成PHAs过程中,通过筛选木质素降解菌、培养PHAs合成菌、优化PHAs的合成工艺及影响因素,可有效提高木质素底物的转化率和PHAs的产量,从而降低生产成本。结论 木质素转化为PHAs的过程虽然面临着一些挑战,但随着技术的不断创新和生产工艺的优化,木质素为底物合成的绿色生物塑料PHAs在包装领域会有广阔的应用前景和发展空间,必将推动包装材料向绿色化、安全化方面发展。     

生物可降解塑料——聚羟基脂肪酸酯（PHA）的生产技术研究

清华大学和中国科学院微生物研究所合作超额完成了可生物降解塑料专题的攻关任务,该专题包括用废糖蜜为原料生产可生物降解塑料聚羟基丁酸酯(PHB)、基因工程菌生产可生物降解塑料PHB、用水解淀粉为原料生产可生物降解塑料PHB及其共聚物PH-BV、可生物降解塑料PHB的改性和应用研究等4个子专题。并在此基础上实现了世界上首次规模化生产第三代PHA——羟基丁酸共聚羟基己酸酯(PHBHHx),为我国的生物可降解塑料工业化研究开辟了广阔的前景。