Meneses Liane, Esmail Asiyah, Matos Mariana, Sevrin Chantal, Grandfils Christian, Barreiros Susana, Reis Maria A M, Freitas Filomena, Paiva Alexandre
LAQV-REQUIMTE, Department of Chemistry, School of Science and Technology, NOVA University Lisbon, 2819-516 Caparica, Portugal.
UCIBIO-Applied Molecular Biosciences Unit, Department of Chemistry, School of Science and Technology, NOVA University Lisbon, 2819-516 Caparica, Portugal.
Bioengineering (Basel). 2022 Jul 8;9(7):302. doi: 10.3390/bioengineering9070302.
Polyhydroxyalkanoate (PHA) recovery from microbial cells relies on either solvent extraction (usually using halogenated solvents) and/or digestion of the non-PHA cell mass (NPCM) by the action of chemicals (e.g., hypochlorite) that raise environmental and health hazards. A greener alternative for PHA recovery, subcritical water (SBW), was evaluated as a method for the dissolution of the NPCM of a mixed microbial culture (MMC) biomass. A temperature of 150 °C was found as a compromise to reach NPCM solubilization while mostly preventing the degradation of the biopolymer during the procedure. Such conditions yielded a polymer with a purity of 77%. PHA purity was further improved by combining the SBW treatment with hypochlorite digestion, in which a significantly lower hypochlorite concentration (0.1%, ) was sufficient to achieve an overall polymer purity of 80%. During the procedure, the biopolymer suffered some depolymerization, as evidenced by the lower molecular weight (M) and higher polydispersity of the extracted samples. Although such changes in the biopolymer's molecular mass distribution impact its mechanical properties, impairing its utilization in most conventional plastic uses, the obtained PHA can find use in several applications, for example as additives or for the preparation of graft or block co-polymers, in which low-M oligomers are sought.
从微生物细胞中回收聚羟基脂肪酸酯（PHA），要么依靠溶剂萃取（通常使用卤代溶剂），要么通过化学物质（如次氯酸盐）作用消化非PHA细胞物质（NPCM），而这些化学物质会带来环境和健康危害。一种回收PHA的更环保替代方法——亚临界水（SBW），被评估为一种溶解混合微生物培养物（MMC）生物质中NPCM的方法。发现150℃的温度是一个折衷选择，既能实现NPCM的溶解，又能在该过程中最大程度地防止生物聚合物降解。在此条件下得到的聚合物纯度为77%。通过将SBW处理与次氯酸盐消化相结合，PHA纯度进一步提高，其中显著更低的次氯酸盐浓度（0.1%）就足以实现聚合物总体纯度达到80%。在该过程中，生物聚合物发生了一些解聚，这从提取样品较低的分子量（M）和较高的多分散性得到证明。尽管生物聚合物分子量分布的这种变化会影响其机械性能，不利于其在大多数传统塑料用途中的应用，但所得的PHA可用于多种应用，例如作为添加剂或用于制备接枝或嵌段共聚物，这些应用中需要低M的低聚物。
