In vitro synthesis of polyhydroxyalkanoate catalyzed by class II and III PHA synthases: a useful technique for surface coatings of a hydrophobic support with PHA

In vitro synthesis of polyhydroxyalkanoates (PHAs) on a hydrophobic support, i.e. highly oriented pyrolytic graphite (HOPG), was performed using class II PHA synthase (PhaC1_Pp) from Pseudomonas putida and class III PHA synthase (PhaEC_Av) from Allochromatium vinosum. Using PhaC1_Pp and 3‐hydroxyoctanoyl‐CoA, a poly(3‐hydroxyoctanoate) [P(3HO)] film was formed on the hydrophobic support with a thickness of a few nanometers, as revealed by atomic force microscopy (AFM). A poly(3‐hydroxybutyrate) [P(3HB)] film was also formed using PhaEC_Av and 3‐hydroxybutyryl‐CoA. AFM observations of the HOPG surface during P(3HB) film formation revealed that polymerized P(3HB) covered HOPG surface within the reaction time, resulting in the formation of a homogeneous ultra‐thin film. This method of ultra‐thin PHA film formation on a hydrophobic support may be applicable to the surface‐coating technique of materials with biodegradable, bioabsorbable, and biocompatible PHAs. Copyright © 2009 Society of Chemical Industry     

聚羟基烷酸酯共混改性研究进展

介绍了聚羟基烷酸酯(PHA)的性能特点以及不足,分别探讨了PHA与天然高分子材料、人工合成高分子材料以及纳米粒子的共混改性研究进展,例如淀粉、丁酸纤维素、聚己内酯、聚碳酸丙烯酯、有机蒙脱土、碳纳米管等。并就共混体系的相容性、结晶性、机械性以及热稳定性进行了总结和评述,展望了PHA的改性方向。     

聚羟基烷基酸酯及其改性研究

介绍了聚羟基烷基酸酯的化学结构,物理性质,详细论述了用天然高分子,化学合成高聚物及生物技术改性聚羟基烷基酸酯的研究进展。     

植物纤维增强聚羟基脂肪酸酯复合材料研究进展

综述了植物纤维与4种聚羟基脂肪酸酯（PHAs）可降解塑料——聚3羟基丁酸酯(PHB)、聚（3羟基丁酸酯3羟基戊酸酯）(PHBV)、聚（3羟基丁酸酯4羟基丁酸酯）［P(3,4)HB］和聚（3羟基丁酸酯3羟基己酸酯）(PHBHHx)制备生物复合材料的研究进展。重点阐述了植物纤维（木纤维、麻纤维和秸秆纤维等）的改性及界面处理方法对PHB和PHBV复合材料的力学、热稳定性和结晶行为等综合性能的影响。最后展望了植物纤维增强PHAs生物可降解复合材料的研究和应用前景。     

Food wastes and sewage sludge as feedstock for an urban biorefinery producing biofuels and added-value bioproducts

The updated Bioeconomy Strategy document “A sustainable bioeconomy for Europe: strengthening the connection between economy, society and the environment”, which was issued by the European Commission in October 2018, encourages the exploitation of organic wastes according to a pyramidal hierarchy in which the extraction of valuable biomolecules, which will be used as they are or as precursors of high-added-value compounds, is a priority in biofuel production. This review considers a biorefinery platform in which food waste and sewage sludge are adopted to produce volatile fatty acids (VFAs) through a dark fermentation process. VFA fermentation is optimized by slightly acid pH (6–7), short hydraulic retention time (1–7 days) and high organic load rate (more than 10 gTS L⁻¹ d⁻¹). Attention has been focused on VFA exploitation for polyhydroxyalkanoate (PHA) production via a ‘feast and famine’ strategy performed in sequencing batch reactors. The obtained PHA yields are around 0.4–0.5 gPHA gCOD⁻¹. Moreover, VFAs allow for the production of biofuels, such as hydrogen and methane, through single- or double-staged anaerobic digestion. Innovative bioelectrochemical upgrade strategies for biogas helps producers to obtain biomethane for the automotive sector. Moreover, biogas has recently been tested for the production of polyhydroxybutyrate, a biodegradable and biocompatible thermoplastic made by microorganisms from C1 carbon sources (CO₂ and CH₄). Digestates from anaerobic bioreactors are still rich in nitrogen and phosphorus compounds. These latter compounds have been identified as critical raw materials due to their low availability in the European Union and to increasing demand from the growing global population. Thus, nutrient recovery from digestate allows users to close the loop of the ‘circular economy’ approach. © 2019 Society of Chemical Industry     

pH对嗜盐混合菌发酵挥发性有机酸混合物合成PHA的影响

嗜盐混合菌发酵生产聚羟基脂肪酸酯（polyhydroxyalkanoate,PHA）具有免灭菌程序、产量高、易提取等优势而被广泛关注。集中考察了pH对嗜盐混合菌（MMCs）发酵混合挥发性有机酸（VFA）生产PHA的影响。研究结果表明,在6.5～8.2范围内pH对PHA合成没有明显影响,过高或者过低的pH都会降低PHA合成速率和VFA的吸收速率。发酵体系的pH影响了嗜盐MMC的PHA产量,但是在酸性和碱性条件下却存在不同的影响机制。碱性环境增大了VFA的解离程度,导致MMC对底物的吸收耗费大量的能量,造成VFA吸收速率的下降。这一作用在pH升高至9.2以上时表现显著。酸性环境下,分子态VFA进入细胞后改变了胞内的pH,降低了相关酶和蛋白质的活性,从而影响了底物的利用。当pH=5.2时微生物代谢及底物利用能耗量降低,导致PHA胞内降解利用率降低,刺激了PHA合成量的提高。PHA组分受pH影响不大,初始pH=5.2～10.2时羟基脂肪酸戊酯（hydroxyvalerate,HV）所占比例维持在34.9%～38.3%范围内。本研究对于进一步利用嗜盐MMC发酵含有混合VFA的废弃物生产PHA具有重要的指导意义。     

Mechanism of enhancement effect of dendrimer on transdermal drug permeation through polyhydroxyalkanoate matrix

The possible application of polyhydroxyalkanoate (PHA) in transdermal drug delivery systems (TDDSs) for tamsulosin was previously reported. PHAs containing the drugs, ketoprofen, clonidine and tamsulosin showed good adhesiveness to the skin model used, that is, shed snake skin, and dispersed well all model drugs tested. The model drugs hardly permeated through snake skin in solution form. However, these drugs permeated well through snake skin from the PHA matrix. It was previously reported that the addition of a dendrimer, a polymeric permeation enhancer, is effective for the TDDS for tamsulosin to establish an effective clinical TDDS. The effect of dendrimer addition was examined in TDDSs for ketoprofen and clonidine. The dendrimer added did not show an enhancement effect on the TDDSs for the two drugs. To investigate the mechanism of the enhancement effect of a dendrimer on the tamsulosin TDDS, X-ray analyses were performed. With dendrimer addition, drug crystallization in PHA was promoted. The crystal in PHA had highly ordered and changed its space group. These findings are very important for exploiting high-performance PHA-based TDDSs.     

复合菌群利用模拟APG协同FNA预处理剩余污泥水解液合成PHA

为探究亚硝酸（FNA）预处理协同烷基糖苷（APG）处理剩余污泥水解液合成聚羟基烷酸酯（PHA）的可行性,本文启动接种两种不同污泥的序批式反应器（SBR）富集PHA产生菌,研究活性污泥复合菌群以模拟APG协同FNA预处理剩余污泥的水解液为底物的PHA合成效果;并采用批次合成实验,考察pH、C/N和C/P对PHA合成量的影响。结果表明：与接种污水厂二沉池污泥的反应器（SBR^#1）相比,接种以葡萄糖为底物驯化成熟的产PHA混合菌的反应器（SBR^#2）在30天时得到的PHA合成量较高;随着富集时间的推移,到117天时,接种污水厂二沉池污泥得到的PHA产生菌性能更优。PHA合成的最佳条件为：pH=8,C/P=100∶0.03,C/N=125∶1。在此条件下,PHA合成量最大,为57.34%。以实际FNA预处理协同APG处理剩余污泥水解液为底物时,PHA的累积合成量为24.43%。该研究结果可丰富污泥合成PHA技术方法,为污泥的处理和资源化利用提供技术支持。