Biomass Science and Conversion Technology, Sandia National Laboratories, 7011 East Ave, Livermore, CA, 94551, USA.
Energy Bioscience Institute, 2151 Berkeley Way, Berkeley, CA, 94704, USA.
Microb Cell Fact. 2019 Mar 18;18(1):54. doi: 10.1186/s12934-019-1099-8.
Due to their high energy density and compatible physical properties, several monoterpenes have been investigated as potential renewable transportation fuels, either as blendstocks with petroleum or as drop-in replacements for use in vehicles (both heavy and light-weight) or in aviation. Sustainable microbial production of these biofuels requires the ability to utilize cheap and readily available feedstocks such as lignocellulosic biomass, which can be depolymerized into fermentable carbon sources such as glucose and xylose. However, common microbial production platforms such as the yeast Saccharomyces cerevisiae are not naturally capable of utilizing xylose, hence requiring extensive strain engineering and optimization to efficiently utilize lignocellulosic feedstocks. In contrast, the oleaginous red yeast Rhodosporidium toruloides is capable of efficiently metabolizing both xylose and glucose, suggesting that it may be a suitable host for the production of lignocellulosic bioproducts. In addition, R. toruloides naturally produces several carotenoids (C40 terpenoids), indicating that it may have a naturally high carbon flux through its mevalonate (MVA) pathway, providing pools of intermediates for the production of a wide range of heterologous terpene-based biofuels and bioproducts from lignocellulose.
Sixteen terpene synthases (TS) originating from plants, bacteria and fungi were evaluated for their ability to produce a total of nine different monoterpenes in R. toruloides. Eight of these TS were functional and produced several different monoterpenes, either as individual compounds or as mixtures, with 1,8-cineole, sabinene, ocimene, pinene, limonene, and carene being produced at the highest levels. The 1,8-cineole synthase HYP3 from Hypoxylon sp. E74060B produced the highest titer of 14.94 ± 1.84 mg/L 1,8-cineole in YPD medium and was selected for further optimization and fuel properties study. Production of 1,8-cineole from lignocellulose was also demonstrated in a 2L batch fermentation, and cineole production titers reached 34.6 mg/L in DMR-EH (Deacetylated, Mechanically Refined, Enzymatically Hydorlized) hydrolysate. Finally, the fuel properties of 1,8-cineole were examined, and indicate that it may be a suitable petroleum blend stock or drop-in replacement fuel for spark ignition engines.
Our results demonstrate that Rhodosporidium toruloides is a suitable microbial platform for the production of non-native monoterpenes with biofuel applications from lignocellulosic biomass.
由于其高能量密度和兼容的物理性质，几种单萜类化合物已被研究为潜在的可再生运输燃料，无论是作为与石油的混合燃料，还是作为在车辆（包括重型和轻型车辆）或航空中使用的替代品。这些生物燃料的可持续微生物生产需要能够利用廉价且易得的原料，如木质纤维素生物质，这些生物质可以解聚成可发酵的碳源，如葡萄糖和木糖。然而，常见的微生物生产平台，如酵母酿酒酵母，本身并不自然能够利用木糖，因此需要进行广泛的菌株工程和优化，以有效地利用木质纤维素原料。相比之下，油脂红酵母 Rhodosporidium toruloides 能够有效地代谢木糖和葡萄糖，这表明它可能是生产木质纤维素生物制品的合适宿主。此外，R. toruloides 天然产生几种类胡萝卜素（C40 萜烯），表明它可能通过其甲羟戊酸（MVA）途径具有自然的高碳通量，为从木质纤维素生产各种异源萜烯基生物燃料和生物制品提供了中间体库。
评估了来自植物、细菌和真菌的 16 种萜烯合酶（TS），以确定它们在 Rhodosporidium toruloides 中生产总共 9 种不同单萜的能力。其中 8 种 TS 具有功能，可产生几种不同的单萜，无论是作为单一化合物还是混合物，1,8-桉树脑、桧烯、侧柏烯、蒎烯、柠檬烯和蒈烯的产量最高。Hypoxylon sp. E74060B 的 1,8-桉树脑合酶 HYP3 在 YPD 培养基中产生了最高的 14.94±1.84mg/L 1,8-桉树脑，因此被选择进一步优化和研究燃料性能。木质纤维素来源的 1,8-桉树脑的生产也在 2L 分批发酵中得到了证明，在 DMR-EH（脱乙酰基、机械精制、酶水解）水解物中，桉树脑的产量达到了 34.6mg/L。最后，研究了 1,8-桉树脑的燃料性能，结果表明它可能是一种适合火花点火发动机的石油混合燃料或替代品燃料。
我们的结果表明，Rhodosporidium toruloides 是一种适合生产具有生物燃料应用的非天然单萜类化合物的微生物平台，可利用木质纤维素生物质作为原料。
Zotero 插件
