Mission Elaine G, Agutaya Jonas Karl Christopher N, Quitain Armando T, Sasaki Mitsuru, Kida Tetsuya
Graduate School of Science and Technology Japan
College of Cross-Cultural and Multidisciplinary Studies Japan
RSC Adv. 2019 Sep 25;9(52):30325-30334. doi: 10.1039/c9ra03594j. eCollection 2019 Sep 23.
Biomass valorization involves breaking down naturally occurring long chain polysaccharides into their constituent monomers. The polysaccharide chain consists of monomers adjoined C (carbon)-O (oxygen) glycosidic linkages that are typically cleaved hydrolytic scission. In this study, we aimed to recover fucose from the polysaccharide fucoidan, which can be extracted from seaweed biomass. We investigated the depolymerisation behavior of fucoidan sourced from two different species of seaweeds, namely (F-UP) and (F-FV). Catalytic depolymerisation experiments were performed using four different carbon-based catalysts - graphene, multiwalled carbon nanotubes (MWCNT), graphene oxide (GO), and reduced graphene oxide (rGO) - under microwave (MW) irradiation. Our results showed that the depolymerisation of fucoidan was best achieved using GO, which was attributed to the abundance of oxygen functionalities on its surface. Furthermore, based on gel permeation chromatography analyses, the depolymerisation of fucoidan was found to follow a two-step process: (1) random scission leading to the production of short-chain oligosaccharides and (2) acid-catalysed hydrolysis of the oligosaccharides to fucose. Because of the longer chain length of F-UP (61 kDa), the highest fucose yield of 17.4% using this species was obtained at a higher temperature of 120 °C in a closed vessel. Meanwhile, in the case of F-FV (1.1 kDa), the highest yield of 54.0% was obtained under reflux conditions at a lower temperature of 104 °C. Our mechanistic study based on semi-empirical quantum calculations also revealed that the recovery of fucose from F-FV is more energetically favoured than from F-UP as a result of their structural differences.
生物质增值涉及将天然存在的长链多糖分解为其组成单体。多糖链由通过C（碳）-O（氧）糖苷键相连的单体组成，这些糖苷键通常通过水解断裂。在本研究中，我们旨在从可从海藻生物质中提取的岩藻多糖中回收岩藻糖。我们研究了源自两种不同海藻物种的岩藻多糖的解聚行为，即（F-UP）和（F-FV）。在微波（MW）辐射下，使用四种不同的碳基催化剂——石墨烯、多壁碳纳米管（MWCNT）、氧化石墨烯（GO）和还原氧化石墨烯（rGO）进行催化解聚实验。我们的结果表明，使用GO能最好地实现岩藻多糖的解聚，这归因于其表面丰富的氧官能团。此外，基于凝胶渗透色谱分析，发现岩藻多糖的解聚遵循两步过程：（1）随机断裂导致产生短链寡糖，（2）寡糖经酸催化水解为岩藻糖。由于F-UP的链长较长（61 kDa），在封闭容器中于较高温度120°C下使用该物种获得了最高的岩藻糖产率17.4%。同时，对于F-FV（1.1 kDa），在较低温度104°C的回流条件下获得了最高产率54.0%。我们基于半经验量子计算的机理研究还表明，由于它们的结构差异，从F-FV中回收岩藻糖在能量上比从F-UP中更有利。
