Hahn Thomas, Alzate Melissa Ortega, Leonhardt Steven, Tamang Pravesh, Zibek Susanne
Bioprocess Development Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB Stuttgart Germany.
Department of Chemical Engineering University of Antioquia El Carmen de Viboral Colombia.
Eng Life Sci. 2024 Mar 7;24(6):2300211. doi: 10.1002/elsc.202300211. eCollection 2024 Jun.
Polyhydroxyalkanoates (PHAs) have gained interest recently due to their biodegradability and versatility. In particular, the chemical compositions of medium-chain-length (mcl)-PHAs are highly diverse, comprising different monomers containing 6-14 carbon atoms. This review summarizes different feedstocks and fermentation strategies to enhance mcl-PHA production and briefly discusses the downstream processing. This review also provides comprehensive details on analytical tools for determining the composition and properties of mcl-PHA. Moreover, this study provides novel information by statistically analyzing the data collected from several reports on mcl-PHA to determine the optimal fermentation parameters (specific growth rate, PHA productivity, and PHA yield from various structurally related and unrelated substrates), mcl-PHA composition, molecular weight (MW), and thermal and mechanical properties, in addition to other relevant statistical values. The analysis revealed that the median PHA productivity observed in the fed-batch feeding strategy was 0.4 g L h, which is eight times higher than that obtained from batch feeding (0.05 g L h). Furthermore, 3-hydroxyoctanoate and -decanoate were the primary monomers incorporated into mcl-PHA. The investigation also determined the median glass transition temperature (-43°C) and melting temperature (47°C), which indicated that mcl-PHA is a flexible amorphous polymer at room temperature with a median MW of 104 kDa. However, information on the monomer composition or heterogeneity and the associated physical and mechanical data of mcl-PHAs is inadequate. Based on their mechanical values, the mcl-PHAs can be classified as semi-crystalline polymers (median crystallinity 23%) with rubber-like properties and a median elongation at break of 385%. However, due to the limited mechanical data available for mcl-PHAs with known monomer composition, identifying suitable processing tools and applications to develop mcl-PHAs further is challenging.
聚羟基脂肪酸酯（PHA）因其生物可降解性和多功能性，近年来受到广泛关注。特别是中链长度（mcl）-PHA的化学组成高度多样化，包含不同的含6-14个碳原子的单体。本综述总结了用于提高mcl-PHA产量的不同原料和发酵策略，并简要讨论了下游加工过程。本综述还详细介绍了用于确定mcl-PHA组成和性质的分析工具。此外，本研究通过对从多篇关于mcl-PHA的报告中收集的数据进行统计分析，提供了新的信息，以确定最佳发酵参数（比生长速率、PHA生产力以及来自各种结构相关和不相关底物的PHA产量）、mcl-PHA组成、分子量（MW）、热性能和机械性能，以及其他相关统计值。分析表明，分批补料策略中观察到的PHA生产力中位数为0.4 g L h，比分批进料（0.05 g L h）高出八倍。此外，3-羟基辛酸酯和-癸酸酯是掺入mcl-PHA的主要单体。该研究还确定了玻璃化转变温度中位数（-43°C）和熔点（47°C），这表明mcl-PHA在室温下是一种柔性无定形聚合物，中位数MW为104 kDa。然而，关于mcl-PHA的单体组成或异质性以及相关物理和机械数据的信息并不充分。基于其机械性能值，mcl-PHA可归类为具有橡胶状性能的半结晶聚合物（中位数结晶度为23%），断裂伸长率中位数为385%。然而，由于具有已知单体组成的mcl-PHA的机械数据有限，进一步开发mcl-PHA的合适加工工具和应用具有挑战性。
