Plastic plays a crucial role in everyday life of human living, nevertheless it represents an undeniable source of land and water pollution. Polyhydroxybutyrate (PHB) is a bio-based and biodegradable polyester, which can be naturally produced by microorganisms capable of converting and accumulating carbon as intracellular granules. Hence, PHB-producing strains stand out as an alternative source to fossil-derived counterparts. However, the extraction strategy affects the recovery efficiency and the quality of PHB. In this study, PHB was produced by a genetically modified Escherichia coli strain and successively extracted using dimethyl carbonate (DMC) and ethanol as alternative solvent and polishing agent to chloroform and hexane. Eventually, a Life Cycle Assessment (LCA) study was performed for evaluating the environmental and health impact of using DMC. Extraction yield and purity of PHB obtained via DMC, were quantified, and compared with those obtained via chloroform-based extraction. PHB yield values from DMC-based extraction were similar to or higher than those achieved by using chloroform (≥ 67%). To optimize the performance of extraction via DMC, different experimental conditions were tested, varying the biomass state (dry or wet) and the mixing time, in presence or in absence of a paper filter. Among 60, 90, 120 min, the mid-value allowed to achieve high extraction yield, both for dry and wet biomass. Physical and molecular dependence on the biomass state and solvent/antisolvent choice was established. The comparative LCA analysis promoted the application of DMC/ethanol rather than chloroform/hexane, as the best choice in terms of health prevention. However, an elevated impact score was achieved by DMC in the environmental-like categories in contrast with a minor contribution by its counterpart. The multifaceted exploration of DMC-based PHB extraction herein reported extends the knowledge of the variables affecting PHB purification process. This work offers novel and valuable insights into PHB extraction process, including environmental aspects not discussed so far. The findings of our research question the DMC as a green solvent, though also the choice of the antisolvent can influence the impact on the examined categories.

中文翻译：

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基于碳酸二甲酯提取聚羟基丁酸酯 (PHB) 的新见解


塑料在人类日常生活中发挥着至关重要的作用，但它也是不可否认的土地和水污染源。聚羟基丁酸酯（PHB）是一种生物基、可生物降解的聚酯，可由能够将碳转化和积累为细胞内颗粒的微生物自然产生。因此，产生 PHB 的菌株作为化石衍生菌株的替代来源脱颖而出。然而，提取策略影响PHB的回收效率和质量。在本研究中，PHB由转基因大肠杆菌菌株生产，并使用碳酸二甲酯（DMC）和乙醇作为氯仿和己烷的替代溶剂和抛光剂连续提取。最终，进行了生命周期评估 (LCA) 研究，以评估使用 DMC 对环境和健康的影响。对通过 DMC 获得的 PHB 的提取率和纯度进行定量，并与通过氯仿提取获得的结果进行比较。基于 DMC 的提取的 PHB 产率值与使用氯仿获得的值相似或更高 (≥ 67%)。为了优化 DMC 提取的性能，测试了不同的实验条件，改变生物质状态（干或湿）和混合时间，有或没有纸过滤器。在 60、90、120 分钟中，中间值可以实现干生物质和湿生物质的高提取率。建立了对生物质状态和溶剂/反溶剂选择的物理和分子依赖性。比较LCA分析促进了DMC/乙醇的应用，而不是氯仿/己烷，成为健康预防方面的最佳选择。 然而，DMC 在类似环境类别中取得了较高的影响分数，而其同行的贡献较小。本文报道的基于 DMC 的 PHB 提取的多方面探索扩展了影响 PHB 纯化过程的变量的知识。这项工作为 PHB 提取过程提供了新颖且有价值的见解，包括迄今为止尚未讨论的环境方面。我们的研究结果对 DMC 作为绿色溶剂提出了质疑，尽管反溶剂的选择也会影响对所检查类别的影响。