Efficient production of 3-hydroxypropionate from fatty acids feedstock in Escherichia coli.

The production of chemicals from renewable biomass resources is usually limited by factors including high-cost processes and low efficiency of biosynthetic pathways. Fatty acids (FAs) are an ideal alternative biomass. Their advantages include high-efficiently producing acetyl-CoA and reducing power, coupling chemical production with CO2 fixation, and the fact that they are readily obtained from inexpensive feedstocks. The important platform chemical 3-hydroxypropionate (3HP) can be produced from FAs as the feedstock with a theoretical yield of 2.49 g/g, much higher than the theoretical yield from other feedstocks. In this study, we first systematically analyzed the limiting factors in FA-utilization pathways in Escherichia coli. Then, we optimized FA utilization in Escherichia coli by using a combination of metabolic engineering and optimization of fermentation conditions. The 3HP biosynthesis module was introduced into a FA-utilizing strain, and the flux balance was finely optimized to maximize 3HP production. The resulting strain was able to produce 3HP from FAs with a yield of 1.56 g/g, and was able to produce 3HP to a concentration of 52 g/L from FAs in a 5-L fermentation process. The strain also could produce 3HP from various type of FAs feedstock including gutter oil. This is the first report of a technique for the efficient production of the platform chemical 3HP from FAs.

Supercritical carbon dioxide-assisted rapid synthesis of few-layer black phosphorus for hydrogen peroxide sensing.

Solutions with large-scale dispersions of 2D black phosphorus (BP), often referred to as phosphorene, are obtained through solvent exfoliation. But, rapid phosphorene synthesis remains a challenge. Furthermore, although the chemical sensing capability of BP-based sensors has been theoretically predicted, its experimental verification remains lacking. In this study, we demonstrate the use of supercritical carbon dioxide-assisted rapid synthesis (5h) of few-layer BP. In addition, we construct a non-enzymatic hydrogen peroxide (H2O2) sensor based on few-layer BP for the first time to utilize BP degradation under ambient conditions. The proposed H2O2 sensor exhibits a considerably lower detection limit of 1 × 10(-7) M compared with the general detection limit of 1 × 10(-7) M-5 × 10(-5)M via electrochemical methods. Overall, the results of this study will not only expand the coverage of BP research but will also identify the important sensing characteristics of BP.