Attenborough Edward, Yazdan Parast Farin, Nosrati Reza, Banaszak Holl Mark M, van 't Hag Leonie
Department of Chemical and Biological Engineering, Monash University, Clayton, VIC, 3800, Australia.
Department of Mechanical and Aerospace Engineering, Monash University, Clayton, VIC, 3800, Australia.
Microb Cell Fact. 2025 Sep 16;24(1):204. doi: 10.1186/s12934-025-02833-7.
The bacterial production of polyhydroxyalkanoates (PHAs), a class of non-toxic, biodegradable, and bio-based polymers, has gained increasing attention as a sustainable alternative to petrochemical plastics. Among PHA producers, Cupriavidus necator H16 and Pseudomonas putida KT2440 are used for their ability to synthesise short- and medium-chain-length PHAs, respectively. While PHAs have been produced from simple hexoses like glucose and fructose, there remains a lack of systematic and integrated analysis linking carbon source, strain selection, monomer composition, and polymer crystallinity to blend behavior in ultrathin films.
PHB and mcl-PHA production using Cupriavidus necator H16 and Pseudomonas putida KT2440 on glucose and fructose were compared herein. C. necator accumulated PHB up to 60 wt% on fructose and 45 wt% on glucose, with high molecular weight (0.7-1.3 MDa), while P. putida produced mcl-PHA up to 22 wt% on fructose and 18 wt% on glucose, with lower molecular weight (46-47 kDa) and a C6 - C12 monomer profile. Notably, C. necator exhibited extreme cell elongation (up to 30 μm) during PHB accumulation on fructose. Extracted polymers were systematically solvent-blended at defined ratios (100:0, 80:20, 60:40, 40:60, and 20:80 PHB:mcl-PHA) and cast into ultrathin films (~ 20 μm) with varying composition. Crystallinity was modelled using a Gaussian fitting approach on FTIR spectra via custom MATLAB code, enabling localised phase analysis and offering a rapid alternative to DSC for thin film crystallinity estimation. While film blends exhibited tunable crystallinity and multiple melting transitions, elongation at break was consistent across compositions, with increases observed at higher mcl-PHA content.
This study provides a systematic comparison of PHAs from C. necator H16 and P. putida KT2440 grown on common hexoses, with full characterisation of monomer composition, molecular weight, and thermal behaviour to guide thin film bioplastic design. Blending PHB and mcl-PHA in ultrathin films revealed reduced melting points and crystallinity, likely due to reduced crystal size from film thickness constraints. This work offers a comparative reference for microbial PHA production and presents a strategy to design bioplastics with tunable properties for temperature-responsive packaging and drug delivery applications.
聚羟基脂肪酸酯（PHA）是一类无毒、可生物降解的生物基聚合物，其细菌生产作为石化塑料的可持续替代品受到越来越多的关注。在PHA生产者中，食酸戴尔福特菌H16和恶臭假单胞菌KT2440分别因其合成短链和中链长度PHA的能力而被使用。虽然PHA已由葡萄糖和果糖等简单己糖生产，但仍缺乏将碳源、菌株选择、单体组成和聚合物结晶度与超薄膜中的共混行为联系起来的系统综合分析。
本文比较了食酸戴尔福特菌H16和恶臭假单胞菌KT2440在葡萄糖和果糖上生产聚（3-羟基丁酸酯）（PHB）和中链长度PHA的情况。食酸戴尔福特菌在果糖上积累的PHB高达60 wt%，在葡萄糖上高达45 wt%，分子量较高（0.7-1.3 MDa），而恶臭假单胞菌在果糖上生产的中链长度PHA高达22 wt%，在葡萄糖上高达18 wt%，分子量较低（46-47 kDa），且具有C6 - C12单体分布。值得注意的是，食酸戴尔福特菌在果糖上积累PHB期间表现出极端的细胞伸长（长达30μm）。将提取的聚合物以规定比例（100:0、80:20、60:40、40:60和20:80的PHB:中链长度PHA）进行系统的溶剂共混，并浇铸成具有不同组成的超薄膜（约20μm）。通过自定义MATLAB代码在傅里叶变换红外光谱上使用高斯拟合方法对结晶度进行建模，能够进行局部相分析，并为薄膜结晶度估计提供了一种快速替代差示扫描量热法的方法。虽然薄膜共混物表现出可调节的结晶度和多个熔融转变，但断裂伸长率在不同组成中是一致的，在较高的中链长度PHA含量下有所增加。
本研究对食酸戴尔福特菌H16和恶臭假单胞菌KT2440在常见己糖上生长的PHA进行了系统比较，全面表征了单体组成、分子量和热行为，以指导薄膜生物塑料的设计。在超薄膜中共混PHB和中链长度PHA显示熔点和结晶度降低，这可能是由于薄膜厚度限制导致晶体尺寸减小。这项工作为微生物PHA生产提供了一个比较参考，并提出了一种设计具有可调性能的生物塑料的策略，用于温度响应包装和药物递送应用。
