Palazzolo Martin A, Garcia-Perez Manuel
Department of Biological Systems Engineering, Washington State University, Pullman 99164, United States.
Department of Biological Systems Engineering, Washington State University, Pullman 99164, United States.
Biotechnol Adv. 2022 Jan-Feb;54:107791. doi: 10.1016/j.biotechadv.2021.107791. Epub 2021 Jun 27.
Lipids are a biorefinery platform to prepare fuel, food and health products. They are traditionally obtained from plants, but those of microbial origin allow for a better use of land and C resources, among other benefits. Several (thermo)chemical and biochemical strategies are used for the conversion of C contained in lignocellulosic biomass into lipids. In particular, pyrolysis can process virtually any biomass and is easy to scale up. Products offer cost-effective, renewable C in the form of readily fermentable molecules and other upgradable intermediates. Although the production of microbial lipids has been studied for 30 years, their incorporation into biorefineries was only described a few years ago. As pyrolysis becomes a profitable technology to depolymerize lignocellulosic biomass into assimilable C, the number of investigations on it raises significantly. This article describes the challenges and opportunities resulting from the combination of lignocellulosic biomass pyrolysis and lipid biosynthesis with oleaginous microorganisms. First, this work presents the basics of the individual processes, and then it shows state-of-the-art processes for the preparation of microbial lipids from biomass pyrolysis products. Advanced knowledge on separation techniques, structure analysis, and fermentability is detailed for each biomass pyrolysis fraction. Finally, the microbial fatty acid platform comprising biofuel, human food and animal feed products, and others, is presented. Literature shows that the microbial lipid production from anhydrosugars, like levoglucosan, and short-chain organic acids, like acetic acid, is straightforward. Indeed, processes achieving nearly theoretical yields form the latter have been described. Some authors have shown that lipid biosynthesis from different lignin sources is biochemically feasible. However, it still imposes major challenges regarding strain performance. No report on the fermentation of pyrolytic lignin is yet available. Research on the microbial uptake of pyrolytic humins remains vacant. Microorganisms that make use of methane show promising results at the proof-of-concept level. Overall, despite some issues need to be tackled, it is now possible to conceive new versatile biorefinery models by combining lignocellulosic biomass pyrolysis products and robust oleaginous microbial cell factories.
脂质是制备燃料、食品和健康产品的生物炼制平台。传统上，脂质是从植物中获取的，但微生物来源的脂质具有诸多优势，比如能更好地利用土地和碳资源。有多种（热）化学和生物化学策略可用于将木质纤维素生物质中所含的碳转化为脂质。特别是，热解几乎可以处理任何生物质，并且易于扩大规模。热解产物以易于发酵的分子和其他可升级中间体的形式提供了具有成本效益的可再生碳。尽管微生物脂质的生产已经研究了30年，但直到几年前才有人描述将其纳入生物炼制过程。随着热解成为将木质纤维素生物质解聚为可同化碳的一项有利可图的技术，对其的研究数量显著增加。本文描述了木质纤维素生物质热解与利用产油微生物进行脂质生物合成相结合所带来的挑战和机遇。首先，这项工作介绍了各个过程的基础知识，然后展示了从生物质热解产物制备微生物脂质的最新工艺。针对每个生物质热解馏分，详细介绍了分离技术、结构分析和发酵性方面的先进知识。最后，介绍了包括生物燃料、人类食品和动物饲料产品等在内的微生物脂肪酸平台。文献表明，从脱水糖（如左旋葡聚糖）和短链有机酸（如乙酸）生产微生物脂质很简单。实际上，已经描述了从后者实现接近理论产量的过程。一些作者表明，从不同木质素来源进行脂质生物合成在生物化学上是可行的。然而，这在菌株性能方面仍然带来重大挑战。目前尚无关于热解木质素发酵的报告。关于微生物对热解腐殖质的摄取研究仍然空白。利用甲烷的微生物在概念验证层面显示出有前景的结果。总体而言，尽管仍有一些问题需要解决，但现在通过将木质纤维素生物质热解产物与强大的产油微生物细胞工厂相结合，有可能构思出新的通用生物炼制模型。
