Abstract：
Medium-chain-length polyhydroxyalkanoates (mcl-PHA) are biobased materials with promising properties for environmentally friendly applications. Due to high production costs, which are related to the cost of the carbon sources combined with conversion insufficiencies, currently only small quantities are produced. This results in a lack of reliable data on properties and application potential for the variety of polymers from different types of production strains. This study investigated the potential for the production of mcl-PHA from volatile fatty acids (VFA) at a larger scale, given their potential as low-cost and sustainable raw material within a carboxylate-platform based biorefinery. Pseudomonas citronellolis (DSMZ 50332) was chosen as the production strain, and acetic acid was selected as the main carbon and energy source. Nitrogen was limited to trigger polymer production, and a fed-batch process using a pH-stat feeding regime with concentrated acid was established. We report successful production, extraction, and characterization of mcl PHA, obtaining a total of 1.76 kg from two 500-litre scale fermentations. The produced polymer was identified as a copolymer of 3-hydroxydecanoate (60.7%), 3-hydroxyoctanoate (37.3%), and 3-hydroxyhexanoate (2.0%) with a weight average molecular weight (Mw) of 536 kDa. NMR analysis indicates the presence of unsaturated side chains, which may offer additional possibilities for modification. The results confirm that there is a potential to produce significant amounts of mcl-PHA with interesting rubber-like properties from waste-derived VFA.
摘要：
中链长度的聚羟基链烷酸酯（mcl-PHA）是生物基材料，具有环保应用的前景。由于生产成本高，这与碳源的成本以及转化不足有关，目前只生产少量。这导致缺乏关于来自不同类型的生产菌株的各种聚合物的性质和应用潜力的可靠数据。这项研究调查了从挥发性脂肪酸（VFA）大规模生产mcl-PHA的潜力，考虑到它们作为基于羧酸盐平台的生物精炼厂中的低成本和可持续原材料的潜力。选择香茅假单胞菌（DSMZ50332）作为生产菌株，选择乙酸作为主要碳源和能源。氮气被限制以触发聚合物生产，并建立了使用浓酸的pH-stat进料制度的分批进料工艺。我们报告生产成功，提取,和mclPHA的表征，从两次500升规模发酵中获得总计1.76公斤。所产生的聚合物被鉴定为3-羟基癸酸酯(60.7%)的共聚物,3-羟基辛酸（37.3%），和3-羟基己酸酯(2.0%),重均分子量(Mw)为536kDa。NMR分析表明存在不饱和侧链，这可能为修改提供额外的可能性。结果证实,存在从源自废物的VFA产生显著量的具有令人感兴趣的橡胶样性质的mcl-PHA的潜力。
