Harnessing the power of microbial autotrophy

Abstract

Autotrophic microorganisms convert CO into biomass by deriving energy from light or inorganic electron donors. These CO-fixing microorganisms have a large, but so far only partially realized, potential for the sustainable production of chemicals and biofuels. Productivities have been improved in autotrophic hosts through the introduction of production pathways and the modification of autotrophic systems by genetic engineering. In addition, approaches are emerging in which CO fixation pathways and energy-harvesting systems are transplanted into heterotrophic model microorganisms. Alternative promising concepts are hybrid production systems of autotrophs and heterotrophs, and bio-inorganic hybrids of autotrophic microorganisms with electrocatalysts or light-harvesting semiconductor materials. In this Review, we discuss recent advances and bottlenecks for engineering microbial autotrophy and explore novel strategies that will pave the way towards improved microbial autotrophic production platforms.

Retinal-Based Proton Pumping in the Near Infrared

“…It has been suggested that PRs can complement oxophototrophy further when their spectral band is shifted bathochromically to utilize photons outside the range of photosynthetically active radiation (PAR; 400–700 nm), 21,22 which is hardly exploited by oxygenic photosynthesis. 23,24 Red-light activation is also highly desired in the field of optogenetics, where microbial rhodopsins like channelrhodopsins are used to modulate the activity of neurons or other mammalian cells by light.…”

Harnessing a methane‐fueled, sediment‐free mixed microbial community for utilization of distributed sources of natural gas

“…This approach offers several industrial benefits, both in its current configuration and as an enabling technology for future enhancements. By converting methane to dissolved inorganic carbon, greenhouse warming potential is reduced more than an order of magnitude (Stocker, ), and engineered autotrophs could be introduced downstream to generate high‐value liquid fuels (Claassens, Sousa, dos Santos, de Vos, & Van der Oost, ; Lan & Liao, ). In addition to building a symbiosis with ANME to enable methane consumption, sulfate‐reducing bacteria can remediate heavy metals (García, Moreno, Ballester, Blázquez, & González, ; Joo, Choi, Kim, Kim, & Oh, ) and produce plastic precursor storage molecules (Hai, Lange, Rabus, & Steinbüchel, ; Wang, Yin, & Chen, ).…”

A warm welcome for alternative CO2 fixation pathways in microbial biotechnology

“…RubisCO has a low catalytic rate, and therefore is generally expressed in high levels, which requires a considerable amount of cellular resources. This resource demand comes on top of the existing high ATP‐demand of the Calvin cycle required to produce common metabolic precursors such as acetyl‐CoA and pyruvate (Claassens et al ., 2016). Furthermore, RubisCO has a major wasteful side‐activity with O 2 in atmospheric conditions.…”

“…Compared to model heterotrophs, such as E. coli and yeast, the available genetic toolboxes for autotrophs are more limited. However, given the ongoing tool development in some biotechnologically relevant autotrophs, these strains should be considered for engineering CO 2 fixation pathways (Claassens et al ., 2016). Promising autotrophs include photoautotrophs, such as the cyanobacterium Synechocystis PCC6803 and anoxygenic phototroph Rhodobacter sphaeroides , and some chemolithoautotrophs, such as Cupriavidus necator (formerly Ralstonia eutropha ), the latter uses hydrogen and CO 2 for autotrophic growth.…”