Data_Sheet_1_Recovery of the PHA Copolymer P(HB-co-HHx) With Non-halogenated Solvents: Influences on Molecular Weight and HHx-Content.pdf

Biodegradable and biocompatible polyhydroxyalkanoates (PHAs) are promising alternatives to conventional plastics. Based on the chain length of their monomers they are classified as short chain length (scl-) or medium chain length (mcl-) PHA polymers. The type of monomers, the composition and the molecular weight (MW) define the polymer properties. To accelerate the use of PHA as a bulk material, the downstream associated costs need to be minimized. This study focuses on the evaluation of non-halogenated solvents, especially acetone as a scl-PHA non-solvent, for the recovery of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) – P(HB-co-HHx) – with an mcl-HHx content >15 mol% and a MW average (Mw) < 2 × 105 Da. Solvents and precipitants were chosen regarding zeotrope formation, boiling point differences, and toxicity. Non-halogenated solvent-precipitant pairs were evaluated regarding the MW characteristics (MWCs) of the extracted polymer. Acetone and 2-propanol as a low toxic and zeotropic solvent-precipitant pair was evaluated at different extraction temperatures and multiple extraction times. The extraction process was further evaluated by using impure acetone for the extraction and implementing a multi-stage extraction process. Additionally, P(HB-co-HHx) extracted with three different solvents was characterized by 1H and 13C-APT NMR. The screening of precipitants resulted in a negative influence on the MWCs by ethanol precipitation for extractions with acetone and ethyl acetate, respectively. It was observed, that extractions with acetone at 70°C extracted a higher fraction of PHA from the cells compared to extractions at RT, but the Mw was decreased by 9% in average. Acetone with a 2-propanol fraction of up to 30% was still able to extract the polymer 95% as efficient as pure acetone. Additionally, when acetone and ethyl acetate were used in a multi-stage extraction process, a two-stage process was sufficient to extract 98–99% of the polymer from the cells. 1H and 13C-APT NMR analysis confirmed the monomer fraction and structure of the extracted polymers and revealed a random copolymer structure. The presented strategy can be further developed to an ecological and economically feasible PHA downstream process and thus contributes to the commercialization of low-cost PHAs.

生物可降解和生物相容性聚羟基烷酸（PHAs）作为传统塑料的潜在替代品，具有广阔的应用前景。根据其单体链长，可分为短链长度（scl-）和中链长度（mcl-）的PHAs聚合物。单体的类型、组成及分子量（MW）决定了聚合物的特性。为加速PHAs作为大宗材料的利用，需尽可能降低其下游相关成本。本研究聚焦于评估非卤化溶剂，尤其是作为scl-PHA非溶剂的丙酮，用于从含mcl-羟基己酸含量大于15摩尔百分比和平均分子量（Mw）小于2 × 10^5 达因的聚（3-羟基丁酸-共-3-羟基己酸）——P(HB-co-HHx)——中进行回收。在选择溶剂和沉淀剂时，考虑到恒沸混合物的形成、沸点差异及毒性。对非卤化溶剂-沉淀剂对进行了分子量特性（MWCs）的评估。丙酮和2-丙醇作为低毒性和恒沸溶剂-沉淀剂对，在多种提取温度和多次提取过程中进行了评估。通过使用不纯丙酮进行提取并实施多阶段提取过程，进一步评估了提取过程。此外，利用三种不同溶剂提取的P(HB-co-HHx)通过1H和13C-APT核磁共振进行表征。沉淀剂的筛选结果显示，在丙酮和乙酸乙酯的提取中，乙醇沉淀分别对分子量特性产生了负面影响。观察到，在70°C下用丙酮提取的PHA从细胞中提取的比例高于室温提取，但平均分子量降低了9%。丙酮中2-丙醇比例高达30%的情况下，仍能以与纯丙酮95%的效率提取聚合物。此外，当丙酮和乙酸乙酯用于多阶段提取过程时，两阶段过程就足以从细胞中提取98–99%的聚合物。1H和13C-APT核磁共振分析证实了提取聚合物的单体比例和结构，并揭示了随机共聚物结构。所提出的策略可进一步发展成为生态和经济上可行的PHAs下游工艺，从而促进低成本PHAs的商业化。