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Abstractp-Nitrophenol (PNP) is an important environmental pollutant and can causes significant environmental and health risks. Compared with the traditional methods, biodegradation is a useful one to completely remove the harmful pollutants from the environment. Here, an engineered strain was first constructed by introducing PNP biodegradation pathway via the hydroquinone (HQ) pathway into Escherichia coli. In the engineered strain BL-PNP, PNP was completely degraded to β-ketoadipate and subsequently enter the metabolites of multiple anabolic pathways. The high tolerance and rapid degradation ability to PNP enable the engineered strain to have the potential to degrade toxic substances. The engineered strain created in this study can be used as a functional strain for bioremediation of PNP and potential toxic intermediates, and the method of assembling aromatic hydrocarbons metabolic pathway can be used to eradicate nitroaromatic pollutants in the environment.

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Biologically available nitrogen is a common limitation to crop productivity in modern agriculture. The endowment of higher plants with the ability to produce their own nitrogenous fertilizers has been attempted for nearly half a century1–4. Here we report that a minimal nitrogen fixation system from Paenibacillus polymyxa5–8 can be used to create an autogenic nitrogen-fixing plant through synthetic biology. We found that the genetically modified Arabidopsis containing the cassette of all nine nif genes (nifBHDKENXhesAnifV) showed some activity of nitrogenase and caused higher biomasses and chlorophyll contents than wild-type plants grown in low-nitrogen or nitrogen-free medium. Then we found that the engineered Arabidopsis displayed resistance to KCN and NaN3, two substrates of nitrogenase9. Furthermore, overexpression of electron transfer component10 in the engineered nif gene-carrying plants resulted in higher nitrogen fixation efficiency. Isotopic labeling analysis using liquid chromatography-tandem mass spectrometry showed that the fixed nitrogen can flow to amino acids and chlorophyll11, 12. This study represents a milestone toward realizing the goal of endowing plants with the capacity for self-fertilization.

Cassava residue is the solid waste generated from the production of tapioca starch and has considerable reuse value. In this study, cassava residue was examined as a hydrolysate for ethanol production, and the effects of different liquid phase oxygen transfer coefficients (k L α) on the production of ethanol from cassava residue hydrolysates were studied. Based on analyses of dissolved oxygen and a set of optimal experimental schemes, dynamic models of cell growth and product synthesis were optimized, using MATLAB. When k L α was 85, fermentation was optimal; the ethanol titer reached 23.14 g L −1 at 72 h and cell growth reached 6.23 g L −1 at 96 h. Additionally, experiments were performed according to the dissolved oxygen curve obtained under these conditions. The resulting ethanol titer was 24.43 g L −1 (72 h) and the cell mass was 6.45 g L −1 (96 h). 84