聚羟基脂肪酸酯的合成和应用

介绍了聚羟基脂肪酸酯(PHA)的合成方法,重点讨论了微生物合成法的菌种、碳源、分离提取及降低PHA生产成本的方法,叙述了作为PHA中的一种-PHB的性能及其改性研究,并论述了PHA在生物医学、农业、电子、食品包装等领域的应用。     

Thermal stability of P(HB‐co‐HV) and its blends with polyalcohols

The thermal stability of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) [P(HB‐co‐HV)] and its blends with poly(propylene glycol)s (PPGs) and castor oil (CO) is reported. The study includes the determination of the degradation kinetics of these materials and the analysis of the effects of the degradation on the mechanical properties and crystallization behavior. Spectroscopy (¹H‐NMR, FTIR), differential scanning calorimetry (DSC), thermogravimetry, and tensile testing techniques are used for the experimental analysis. A chain‐scission degradation mechanism is confirmed by the formation of vinyl groups. Two temperature ranges are investigated. In the range closest to the melting point, 100–200°C, where the blend does not exhibit weight reduction, a fast and sensible loss of molecular weight and tensile strength was detected. The second temperature range, 200–400°C, is characterized by mass loss by pyrolysis. In this range, different kinetic models of the degradation process are proposed. Polyalcohol addition produces opposite effects, while the addition of PPG enhances the degradation of P(HB‐co‐HV). When CO is added, the thermal stability of the blend increases. Mechanical properties of the blends before and after degradation were determined. The tensile modulus increases at the first step of degradation and decreases with the degradation time. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2889–2900, 2000     

微生物法合成生物高分子——聚羟基脂肪酸(酯)进展

生物高分子不但具有重要的生理作用,而且以其卓越的结构特性广泛应用于工业领域。微生物法合成生物高分子具有原料来源丰富、反应条件温和、易规模化生产等优点,正在逐渐成为生产天然高分子聚合物的重要方法。文中系统阐述了聚羟基脂肪酸(酯)天然高分子聚合物的微生物法合成途径、高产菌株筛选、发酵过程优化策略、产物提取及工业化生产前景和应用领域,以期为天然生物高分子聚合物的深入研究和广泛应用提供借鉴。     

Miscibility of natural polyhydroxyalkanoate blend with controllable material properties

Polyhydroxyalkanoate (PHA) copolyesters were synthesized by Cupriavidus necator cells in continuous feeding of cosubstrates. During the PHA accumulation phase, the composition of 3‐hydroxybutyrate (3HB), 3‐hydroxyvalerate (3HV), and 4‐hydroxyvalerate (4HV) of the copolyesters changed with time, resulting in a change in their miscibility. The as‐produced PHA finally became a miscible blend of copolymers with a broad chemical composition distribution. The good miscibility and low crystallinity of the natural P(3HB‐co‐3HV‐co‐4HV) blend lead to a remarkable increase in ductility and elongation at break. It indicates that the material properties of copolyesters can be tailored via feeding control of cosubstrates. It was also found that the fractions of natural PHA blend exhibited distinctive thermal behavior and the overall behavior of the as‐produced PHA blend was primarily dependent on a fraction of high 3HB content. The material properties of a PHA blend are therefore not determined by its overall chemical composition but more likely by the combined effect of individual copolyesters or fractions. Moreover, the degree of X‐ray crystallinity of random P(3HB‐co‐3HV‐co‐4HV) blend declined significantly with the increase of 3HV and 4HV content, in contrast to the high crystallinity of well‐known P(3HB‐co‐3HV) copolyesters. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Revealing the Phenotypic and Genomic Background for PHA Production from Rapeseed-Biodiesel Crude Glycerol Using Photobacterium ganghwense C2.2

Polyhydroxyalkanoates (PHA) are promising biodegradable and biocompatible bioplastics, and extensive knowledge of the employed bacterial strain’s metabolic capabilities is necessary in choosing economically feasible production conditions. This study aimed to create an in-depth view of the utilization of Photobacterium ganghwense C2.2 for PHA production by linking a wide array of characterization methods: metabolic pathway annotation from the strain’s complete genome, high-throughput phenotypic tests, and biomass analyses through plate-based assays and flask and bioreactor cultivations. We confirmed, in PHA production conditions, urea catabolization, fatty acid degradation and synthesis, and high pH variation and osmotic stress tolerance. With urea as a nitrogen source, pure and rapeseed-biodiesel crude glycerol were analyzed comparatively as carbon sources for fermentation at 20 °C. Flask cultivations yielded 2.2 g/L and 2 g/L PHA at 120 h, respectively, with molecular weights of 428,629 g/mol and 81,515 g/mol. Bioreactor batch cultivation doubled biomass accumulation (10 g/L and 13.2 g/L) in 48 h, with a PHA productivity of 0.133 g/(L·h) and 0.05 g/(L·h). Thus, phenotypic and genomic analyses determined the successful use of Photobacterium ganghwense C2.2 for PHA production using urea and crude glycerol and 20 g/L NaCl, without pH adjustment, providing the basis for a viable fermentation process.     

The Influence of Novel,Biocompatible, and Bioresorbable Poly(3-hydroxyoctanoate) Dressings on Wound Healing in Mice

The human body’s natural protective barrier, the skin, is exposed daily to minor or major mechanical trauma, which can compromise its integrity. Therefore, the search for new dressing materials that can offer new functionalisation is fully justified. In this work, the development of two new types of dressings based on poly(3-hydroxyoctanoate) (P(3HO)) is presented. One of the groups was supplemented with conjugates of an anti-inflammatory substance (diclofenac) that was covalently linked to oligomers of hydroxycarboxylic acids (Oli-dicP(3HO)). The novel dressings were prepared using the solvent casting/particulate leaching technique. To our knowledge, this is the first paper in which P(3HO)-based dressings were used in mice wound treatment. The results of our research confirm that dressings based on P(3HO) are safe, do not induce an inflammatory response, reduce the expression of pro-inflammatory cytokines, provide adequate wound moisture, support angiogenesis, and, thanks to their hydrophobic characteristics, provide an ideal protective barrier. Newly designed dressings containing Oli-dicP(3HO) can promote tissue regeneration by partially reducing the inflammation at the injury site. To conclude, the presented materials might be potential candidates as excellent dressings for wound treatment.     

Production of butanol and polyhydroxyalkanoate from industrial waste by Clostridium beijerinckii ASU10

This study demonstrated a biotechnological approach for simultaneous production of low‐cost H₂, liquid biofuels, and polyhydroxyalkanoates (PHAs) by solventogenic bacterium (Clostridium beijerinckii) from renewable industrial wastes such as molasses and crude glycerol. C beijerinckii ASU10 (KF372577) exhibited considerable performance for hydrogen production of 5.1 ± 0.84 and 11 ± 0.44 mL H₂ h^?1 on glycerol and sugarcane molasses, respectively. The total acetone‐butanol‐ethanol (ABE) generation from glycerol and molasses was 9.334 ± 2.98 and 10.831 ± 4.1 g L^?1, respectively. ABE productivity (g L^?1 h^?1) was 0.0486 and 0.0564 with a yield rate (g g^?1) up to 0.508 and 0.493 from glycerol and molasses fermentation, respectively. The PHA yields from glycerol and sugarcane molasses were 84.37% and 37.97% of the dried bacterial biomass, respectively. Additionally, the ultrathin section of C beijerinckii ASU10 showed that PHA granules were accumulated more densely on glycerol than molasses. Gas chromatography–mass spectrometry (GC‐MS) analysis confirmed that the PHAs obtained from molasses fermentation included 3‐hydroxybutyrate (47.3%) and 3‐hydroxyoctanoate (52.7%) as the main constituents. Meanwhile, 3‐hydroxybutyrate represented the sole monomer of PHA produced from glycerol fermentation. This study demonstrated that C beijerinckii ASU10 (KF372577) is a potent strain for low‐cost PHA production depending on its high potential to produce high‐energy biofuel and other valuable compounds from utilization of organic waste materials.     

Novel spray-dried PHA microparticles for antitumor drug release

The production of poly-3-hydroxybutyrate (P3HB) and poly-3-hydroxybutyrate/polyethylene glycol (PEG)-based microparticles, loaded with antitumor drugs paclitaxel (PTX) and 5-Fluorouracil (5-FU) by spray-drying technique, was investigated. The average diameter of microparticles was found to be 3.4?±?0.5?µm and zeta potential was about ?44?mV. The addition of surfactant PEG did not show any effect on the morphological characteristics of the particles. But the chemical structure of drug influenced on the properties. Microparticles had heterogeneous pores on the surface when the hydrophobic PTX was encapsulated. It was established that the addition of surfactant positively influenced on the properties of particles and led to the loading of 5-FU directly into the matrix. This is confirmed by the results of electron microscopy and dynamics of drug release in vitro. As a whole, the release profiles of PTX and 5-FU from composite P3HB/PEG microparticles were less than from P3HB microparticles. The results of the morphological evaluation of Hela cells demonstrated that the use of cytostatic drugs loaded in P3HB microparticles induces morphological changes associated with apoptosis (chromatin condensation, core fragmentation, margination of nucleus). Thus, the obtained results can serve as the basis for the development of new antitumor drugs of prolonged action, intended for various modes of administration.     

Pseudomonas putida KT2442制备中长链聚羟基烷酸酯

初步探讨了利用PseudomonasputidaKT2442制备中长链聚羟基烷酸酯(MCL PHAs)的工艺,考察了不同碳源对菌体生长和产物合成的影响。在2.5L发酵罐上采用高密度细胞培养制备:以油酸为碳源,细胞干重达120g L,MCL PHAs质量浓度达40g L,产物质量分数为34%,生产速率为0.965g·L-1·h-1;以玉米油水解物为碳源,细胞干重达105g L,MCL PHAs达28g L,产物质量分数为26.5%,生产速率为0.667g·L-1·h-1。以玉米油水解物为碳源所得细胞浓度、产物浓度与以油酸为碳源所得结果比较接近,有利于降低生产成本。     

动胶菌发酵生产可降解塑料PHAs

选育能高产聚羟基烷酸的优良菌株,采用最佳的发酵条件是实现细菌发酵法生产可降解塑料工业化应用的关键因素之一。因此对分离自活性污泥中的菌株Zoogloeasp.GY3进行了3L发酵罐的发酵条件研究。结果表明,罐的通气量、转速是影响最终发酵结果的主要因素,其最佳条件为在装液量为1800mL的条件下,通气量为1L/(L.min),20h之前的最佳搅拌速度为350r/min,20h之后的最佳搅拌速度为500r/min。流加控制发酵液糖浓度维持在2.5%,发酵结束后细胞生物量高达53.74g/L,PHAs质量浓度为45.9g/L,PHAs含量提高到85.4%。