Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, 30602, USA.
Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, 27695, USA.
J Ind Microbiol Biotechnol. 2020 Aug;47(8):585-597. doi: 10.1007/s10295-020-02299-z. Epub 2020 Aug 11.
Caldicellulosiruptor bescii is the most thermophilic cellulolytic organism yet identified (T 78 °C). It grows on untreated plant biomass and has an established genetic system thereby making it a promising microbial platform for lignocellulose conversion to bio-products. Here, we investigated the ability of engineered C. bescii to generate alcohols from carboxylic acids. Expression of aldehyde ferredoxin oxidoreductase (aor from Pyrococcus furiosus) and alcohol dehydrogenase (adhA from Thermoanaerobacter sp. X514) enabled C. bescii to generate ethanol from crystalline cellulose and from biomass by reducing the acetate produced by fermentation. Deletion of lactate dehydrogenase in a strain expressing the AOR-Adh pathway increased ethanol production. Engineered strains also converted exogenously supplied organic acids (isobutyrate and n-caproate) to the corresponding alcohol (isobutanol and hexanol) using both crystalline cellulose and switchgrass as sources of reductant for alcohol production. This is the first instance of an acid to alcohol conversion pathway in a cellulolytic microbe.
贝氏考尔德氏菌是迄今发现的最耐热的纤维素分解菌（T 78°C）。它可以在未经处理的植物生物质上生长，并且具有已建立的遗传系统，因此它是一种很有前途的微生物平台，可以将木质纤维素转化为生物制品。在这里，我们研究了工程化的 C. bescii 从羧酸生成醇的能力。醛-铁氧还蛋白氧化还原酶（来自 Pyrococcus furiosus 的 aor）和醇脱氢酶（来自 Thermoanaerobacter sp. X514 的 adhA）的表达使 C. bescii 能够从结晶纤维素和生物质中生成乙醇，方法是还原发酵产生的乙酸盐。在表达 AOR-Adh 途径的菌株中缺失乳酸脱氢酶会增加乙醇的产量。工程菌株还使用结晶纤维素和柳枝稷作为还原剂将外源供应的有机酸（异丁酸和正己酸）转化为相应的醇（异丁醇和正己醇）。这是纤维素分解微生物中酸到醇的转化途径的首例。
