Photo-degradation of five neonicotinoids in water of different quality.

a = imidacloprid, b = acetamiprid, c = clothianidin, d = thiamethoxam, and e = dinotefuran.</p

Photo-degradation of five neonicotinoids under different light source irradiation.

a = imidacloprid, b = acetamiprid, c = clothianidin, d = thiamethoxam, and e = dinotefuran.</p

The effect of bamboo vinegar on the photo-degradation of five neonicotinoids.

a = imidacloprid, b = acetamiprid, c = clothianidin, d = thiamethoxam, and e = dinotefuran.</p

The structures of five neonicotinoids.

The structures of five neonicotinoids.</p

Photo-degradation pathways and products of five neonicotinoids.

a = imidacloprid, b = acetamiprid, c = clothianidin, d = thiamethoxam, and e = dinotefuran.</p

Photo-degradation of five neonicotinoids at different initial concentrations.

a = imidacloprid, b = acetamiprid, c = clothianidin, d = thiamethoxam, and e = dinotefuran.</p

Photo-degradation of five neonicotinoids at different pH values.

Photo-degradation of five neonicotinoids at different pH values.</p

Metabolic Engineering of <i>Escherichia coli</i> for Astragalin Biosynthesis

Astragalin (kaempferol 3-<i>O</i>-glucoside) is used as a standard to assess the quality of <i>Radix astragali</i> and has exhibited a number of biological properties. In this work, we screened several UDP-dependent glycosyltransferases (UGT) for their potential as efficient biocatalysts for astragalin synthesis. The highest astragalin production with 285 mg/L was detected in the recombinant strain expressing UGT from <i>Arabidopis thaliana</i> (AtUGT78D2). To further improve astragalin production, an efficient UDP-glucose synthesis pathway was reconstructed in the recombinant strain by introducing sucrose permease, sucrose phosphorylase, and uridylyltransferase. On the basis of those results, a recombinant strain, BL21-II, was constructed to produce astragalin. By optimizing conversion conditions, astragalin production was increased from 570 to 1708 mg/L. The production was scaled up using a fed-batch fermentation, and maximal astragalin production was 3600 mg/L, with a specific productivity of 150 mg/L/h after 24 h incubation and a corresponding molar conversion of 91.9%, the highest yield reported to date