Synthetic Formatotrophs for One-Carbon Biorefinery.

The use of CO2 as a carbon source in biorefinery is of great interest, but the low solubility of CO2 in water and the lack of efficient CO2 assimilation pathways are challenges to overcome. Formic acid (FA), which can be easily produced from CO2 and more conveniently stored and transported than CO2, is an attractive CO2-equivalent carbon source as it can be assimilated more efficiently than CO2 by microorganisms and also provides reducing power. Although there are native formatotrophs, they grow slowly and are difficult to metabolically engineer due to the lack of genetic manipulation tools. Thus, much effort is exerted to develop efficient FA assimilation pathways and synthetic microorganisms capable of growing solely on FA (and CO2). Several innovative strategies are suggested to develop synthetic formatotrophs through rational metabolic engineering involving new enzymes and reconstructed FA assimilation pathways, and/or adaptive laboratory evolution (ALE). In this paper, recent advances in development of synthetic formatotrophs are reviewed, focusing on biological FA and CO2 utilization pathways, enzymes involved and newly developed, and metabolic engineering and ALE strategies employed. Also, future challenges in cultivating formatotrophs to higher cell densities and producing chemicals from FA and CO2 are discussed.

Escherichia coli is engineered to grow on CO2 and formic acid.

We engineered Escherichia coli to grow on CO2 and formic acid alone by introducing the synthetic CO2 and formic acid assimilation pathway, expressing two formate dehydrogenase genes, fine-tuning metabolic fluxes and optimizing the levels of cytochrome bo3 and bd-I ubiquinol oxidase. Our engineered strain can grow to an optical density at 600 nm of 7.38 in 450 h, and shows promise as a platform strain growing on CO2 and formic acid alone.

Alternative Regional Flaps When Anterolateral Thigh Flap Perforator is not Feasible.

This paper presents the scheme to select alternative flaps limited to the region of the ipsilateral thigh when the perforator of the anterolateral thigh flap is not feasible. Total of 564 consecutive microsurgery cases using anterolateral thigh perforator flap was reviewed from March of 2001 to January of 2009. Total of 12 cases used a contingent flap due to anatomical and technical complications of the anterolateral thigh perforator. The alternatives were skin perforator flaps adjacent to the initial flap (3 cases of upper anterolateral thigh flap, 4 cases of anteromedial thigh flap), vastus lateralis muscle flap with skin graft (2 cases), and anterolateral thigh flap as septocutaneous flap without a prominent perforator on the septum (3 cases). All flaps survived and provided coverage as planned but one case using septocutaneous flap without a prominent perforator was noted with partial necrosis. Adjacent flaps around the anterolateral thigh perforator flap may provide useful alternative flaps in cases of failed elevation. Limiting the contingent secondary flap to this region may reduce further donor site morbidity and still provide an adequate flap for reconstruction.