Neol Biosolutions, SA, Avicena, 4. Parque Tecnológico de la Salud, 18016, Granada, Spain.
Appl Microbiol Biotechnol. 2018 Apr;102(7):3287-3300. doi: 10.1007/s00253-018-8810-2. Epub 2018 Feb 20.
Improving the yield of carbohydrate to lipid conversion and lipid productivity are two critical goals to develop an economically feasible process to commercialize microbial oils. Lignocellulosic sugars are potential low-cost carbon sources for this process but their use is limited by the toxic compounds produced during biomass pretreatment at high solids loading, and by the pentose sugars (mainly xylose) which are not efficiently metabolized by many microorganisms. Adaptive laboratory evolution was used to select a Rhodosporidium toruloides strain with robust growth in non-detoxified wheat straw hydrolysates, produced at 20% solids loading, and better xylose consumption rate. An arabinose-inducible cre-lox recombination system was developed in this evolved strain that was further engineered to express a second copy of the native DGAT1 and SCD1 genes under control of the native xylose reductase (XYL1) promoter. Fed-batch cultivation of the engineered strain in 7-L bioreactors produced 39.5 g lipid/L at a rate of 0.334 g/Lh and 0.179 g/g yield, the best results reported in R. toruloides with non-detoxified lignocellulosic hydrolysates to date.
提高碳水化合物向油脂转化的得率和油脂生产力是开发经济可行的商业化微生物油脂工艺的两个关键目标。木质纤维素糖是该工艺的潜在低成本碳源，但由于在高固体负荷下生物质预处理过程中产生的有毒化合物，以及许多微生物不能有效代谢的戊糖（主要是木糖），其使用受到限制。适应性实验室进化被用于选择一株罗地红酵母（Rhodosporidium toruloides）菌株，该菌株在未经解毒的小麦秸秆水解物中具有稳健的生长能力，固体负荷为 20%，并且具有更好的木糖消耗率。在该进化菌株中开发了一种阿拉伯糖诱导的 cre-lox 重组系统，该系统进一步被工程化为在天然木糖还原酶（XYL1）启动子的控制下表达第二个天然 DGAT1 和 SCD1 基因的拷贝。在 7-L 生物反应器中进行工程菌株的分批补料培养，以 0.334 g/Lh 的速度产生了 39.5 g/L 的油脂，得率为 0.179 g/g，这是迄今为止用未经解毒的木质纤维素水解物在罗地红酵母中报道的最佳结果。
