Kim Dong Hyun, Liu Jing-Jing, Lee Jae Won, Pelton Jeffrey G, Yun Eun Ju, Yu Sora, Jin Yong-Su, Kim Kyoung Heon
Department of Biotechnology, Graduate School, Korea University, Seoul 02841, South Korea.
Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
Green Chem. 2020 Mar 7;22(5):1776-1785. doi: 10.1039/c9gc04265b. Epub 2020 Feb 24.
Recently, the utilization of renewable biomass instead of fossil fuels for producing fuels and chemicals is receiving much attention due to the global climate change. Among renewable biomass, marine algae are gaining importance as third generation biomass feedstocks owing to their advantages over lignocellulose. Particularly, red macroalgae have higher carbohydrate contents and simpler carbohydrate compositions than other marine algae. In red macroalgal carbphydrates, 3,6-anhydro-L-galactose (AHG) is the main sugar composing agarose along with D-galactose. However, AHG is not a common sugar and is chemically unstable. Thus, not only AHG but also red macroalgal biomass itself cannot be efficiently converted or utilized. Here, we biologically upgraded AHG to a new platform chemical, its sugar alcohol form, 3,6-anhydro-l-galactitol (AHGol), an anhydrohexitol. To accomplish this, we devised an integrated process encompassing a chemical hydrolysis process for producing agarobiose (AB) from agarose and a biological process for converting AB to AHGol using metabolically engineered to efficiently produce AHGol from agarose with high titers and yields. AHGol was also converted to an intermediate chemical for plastics, isosorbide. To our knowledge, this is the first demonstration of upgrading a red macroalgal biomass component to a platform chemical via a new biological route, by using an engineered microorganism.
近年来，由于全球气候变化，利用可再生生物质而非化石燃料来生产燃料和化学品受到了广泛关注。在可再生生物质中，海藻作为第三代生物质原料正变得越来越重要，因为它们相对于木质纤维素具有优势。特别是，红藻比其他海藻具有更高的碳水化合物含量和更简单的碳水化合物组成。在红藻碳水化合物中，3,6-脱水-L-半乳糖（AHG）是与D-半乳糖一起构成琼脂糖的主要糖类。然而，AHG并非常见糖类，且化学性质不稳定。因此，不仅AHG，而且红藻生物质本身都无法得到有效转化或利用。在此，我们通过生物学方法将AHG升级为一种新的平台化学品，即其糖醇形式3,6-脱水-L-半乳糖醇（AHGol），一种脱水己糖醇。为实现这一目标，我们设计了一个集成工艺，该工艺包括从琼脂糖生产琼脂二糖（AB）的化学水解过程以及使用代谢工程将AB转化为AHGol的生物过程，从而能够从琼脂糖高效地生产出高滴度和高产量的AHGol。AHGol还被转化为塑料的一种中间化学品异山梨醇。据我们所知，这是首次通过一种新的生物途径，利用工程微生物将红藻生物质成分升级为平台化学品的实例。
