Mongili Beatrice, Abdel Azim Annalisa, Fraterrigo Garofalo Silvia, Batuecas Esperanza, Re Angela, Bocchini Sergio, Fino Debora
Department of Science and Applied Technology (DISAT), Polytechnic University of Turin, Corso Duca degli Abruzzi 24, 10129, Turin, Italy.
Centre for Sustainable Future Technology (CSFT), Italian Institute of Technology, Via Livorno 60, 10144, Turin, Italy.
Biotechnol Biofuels. 2021 Jan 7;14(1):13. doi: 10.1186/s13068-020-01849-y.
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.
塑料在人类日常生活中起着至关重要的作用，然而它也是土地和水污染不可否认的来源。聚羟基丁酸酯（PHB）是一种生物基且可生物降解的聚酯，可由能够将碳转化并积累为细胞内颗粒的微生物天然产生。因此，产PHB菌株作为化石衍生同类产品的替代来源脱颖而出。然而，提取策略会影响PHB的回收效率和质量。在本研究中，通过基因工程改造的大肠杆菌菌株生产PHB，随后使用碳酸二甲酯（DMC）和乙醇作为氯仿和己烷的替代溶剂和精制剂进行提取。最终，进行了生命周期评估（LCA）研究，以评估使用DMC的环境和健康影响。
对通过DMC获得的PHB的提取产率和纯度进行了量化，并与通过基于氯仿的提取获得的产率和纯度进行了比较。基于DMC的提取的PHB产率值与使用氯仿获得的产率值相似或更高（≥67%）。为了优化通过DMC的提取性能，测试了不同的实验条件，改变了生物质状态（干或湿）和混合时间，有无纸质过滤器。在60、90、120分钟中，中间值对于干生物质和湿生物质都能实现高提取产率。建立了对生物质状态以及溶剂/反溶剂选择的物理和分子依赖性。比较LCA分析促进了DMC/乙醇而非氯仿/己烷的应用，因为就健康预防而言这是最佳选择。然而，与氯仿相比，DMC在类似环境的类别中获得了较高的影响得分。
本文报道的基于DMC的PHB提取的多方面探索扩展了对影响PHB纯化过程的变量的认识。这项工作为PHB提取过程提供了新颖且有价值的见解，包括迄今为止未讨论的环境方面。我们研究的结果对DMC作为绿色溶剂提出了质疑，不过反溶剂的选择也会影响对所研究类别的影响。
