Dynamic control of microbial metabolism is an effective strategy to improve chemical production in fermentations. While dynamic control is most often implemented using chemical inducers, optogenetics offers an attractive alternative due to the high tunability and reversibility afforded by light. However, a major concern of applying optogenetics in metabolic engineering is the risk of insufficient light penetration at high cell densities, especially in large bioreactors. Here, we present a new series of optogenetic circuits we call OptoAMP, which amplify the transcriptional response to blue light by as much as 21.8-fold compared to the basal circuit (OptoEXP). These circuits show as much as a 41-fold induction between dark and light conditions, efficient activation at light doses as low as ~1%, and strong homogeneous light-induction in bioreactors of at least 5L, with limited illumination at cell densities above 40 OD600. We demonstrate the ability of OptoAMP circuits to control engineered metabolic pathways in novel three-phase fermentations using different light schedules to control enzyme expression and improve production of lactic acid, isobutanol, and naringenin. These circuits expand the applicability of optogenetics to metabolic engineering.

中文翻译：

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光诱导代谢控制的光遗传放大电路

动态控制微生物代谢是提高发酵过程中化学物质产生的有效策略。虽然动态控制最常使用化学诱导剂来实现，但光遗传学由于光提供的高可调性和可逆性而提供了一种有吸引力的选择。然而，将光遗传学应用于代谢工程的一个主要问题是在高细胞密度下，尤其是在大型生物反应器中，光穿透不足的风险。在这里，我们介绍了一个称为OptoAMP的新系列光遗传学电路，与基础电路（OptoEXP）相比，它对蓝光的转录反应最多可放大21.8倍。这些电路在黑暗和明亮条件下显示出多达41倍的感应强度，在低至〜1％的光剂量下仍能有效激活，生物反应器中至少5L的均匀强光诱导，且在40 OD600以上的细胞密度下照明受限。我们展示了OptoAMP电路使用不同的光照方案来控制新型表达的三相发酵中工程化的代谢途径的能力，以控制酶的表达并改善乳酸，异丁醇和柚皮素的生产。这些电路扩展了光遗传学在代谢工程中的适用性。