Department of Chemistry and Biochemistry, Institute of Paper Science and Technology, Georgia Institute of Technology, 500 10th Street, NW, Atlanta, GA 30332, USA.
Appl Microbiol Biotechnol. 2012 Jan;93(2):891-900. doi: 10.1007/s00253-011-3743-z. Epub 2011 Dec 10.
Although economically efficient biomass conversion depends on the utilization of the complete cell wall (biorefinery concept), including polysaccharides and lignin, current biofuels research concentrate mostly on cellulose conversion, while lignin is viewed as a side-product that is used primarily as a thermal resource. Microbiological conversion of lignin is almost exclusive to fungi, usually resulting in increased cell mass and lignolytic enzymes. Some bacteria can also degrade lignin-related compounds using the β-ketoadipate pathway; for example, Rhodococcus opacus DSM 1069 can degrade coniferyl alcohol and grow on it as sole carbon source. Moreover, this strain belongs to the actinomycetes group that is also known for oleaginous species with lipid accumulation over 20%. Present work shows that R. opacus DSM 1069 and PD630 strains under nitrogen limiting conditions can convert lignin model compounds into triacylglycerols, also known as neutral lipids. 4-Hydroxybenzoic and vanillic acid lignin model compounds were used as sole carbon sources, and after brief adaptation periods, the cells not only began growing but accumulated lipids to the level of oleaginicity. These lipids were extracted for transesterification and analysis of fatty acid methyl esters showed good composition for biodiesel applications with no aromatics. Furthermore, the two strains showed distinct substrate metabolism and product profiles.
虽然经济高效的生物质转化依赖于完整细胞壁的利用（生物炼制概念），包括多糖和木质素，但当前的生物燃料研究主要集中在纤维素转化上，而木质素被视为主要用作热资源的副产物。木质素的微生物转化几乎仅限于真菌，通常导致细胞质量和木质素降解酶增加。一些细菌也可以使用β-酮戊二酸途径降解与木质素相关的化合物；例如，红球菌（Rhodococcus opacus）DSM 1069 可以降解松柏醇并将其作为唯一碳源进行生长。此外，该菌株属于放线菌组，该组的特征还包括能够积累超过 20%脂质的油脂性物种。目前的工作表明，在氮限制条件下，红球菌（Rhodococcus opacus）DSM 1069 和 PD630 菌株可以将木质素模型化合物转化为三酰基甘油，也称为中性脂质。4-羟基苯甲酸和香草酸木质素模型化合物被用作唯一碳源，经过短暂的适应期，细胞不仅开始生长，而且还将脂质积累到油脂性水平。这些脂质被提取用于酯交换，脂肪酸甲酯的分析表明，芳香族化合物含量低，非常适合生物柴油应用。此外，这两个菌株表现出明显的底物代谢和产物特征。
