Radical-Mediated Decarboxylative C-C and C-S Couplings of Carboxylic Acids via Iron Photocatalysis.

Despite the significant success of decarboxylative radical reactions, the catalytic systems vary considerably upon different radical acceptors, requiring renewed case-by-case reaction optimization. Herein, we developed an iron catalytic condition that enables the highly efficient decarboxylation of various carboxylic acids for a range of radical transformations. This operationally simple protocol was amenable to a wide array of radical acceptors, delivering structurally diverse oxime ethers, alkenylation, alkynylation, thiolation, and amidation products in useful to excellent yields (>40 examples, up to 95% yield).

Radical Phosphorylation of Aliphatic C-H Bonds via Iron Photocatalysis.

The synthesis of tertiary phosphines(III) has been a long-standing challenge in synthetic chemistry because of inevitable issues including harsh conditions, sensitive organometallic reagents, and prefunctionalized substrates in traditional synthesis. Herein, we report a strategically novel C(sp3)-H bond phosphorylation that enables the assembly of structurally diverse tertiary phosphines(III) from industrial phosphine(III) sources under mild photocatalytic conditions. The merger of ligand-to-metal charge transfer (LMCT) of FeCl3 with the hydrogen atom-transfer (HAT) process is the key for the generation of alkyl radicals from hydrocarbons. Strikingly, this catalytic system can be successfully applied for the polymerization of electron-deficient alkenes.

Paper-Based Enzymatic Colorimetric Assay for Rapid Malathion Detection.

Due to their unique properties, paper-based biosensors have attracted attention as inexpensive devices for on-site analysis. To achieve fast and sensitive detection of analytes, immobilization of enzymes with high apparent activities on paper is highly desirable; however, this is challenging. Herein, we report an improved approach to attach a malathion degrading enzyme, PoOPHM9, on paper via an interlocking network of Pluronic F127 (PF127)-poly(acrylic acid)-enzyme conjugates. The addition of PF127 improved retention of enzymatic activity as the apparent kinetic constant Vmax of the immobilized enzyme increased two-fold compared with the paper prepared without PF127. The PF127-poly(acrylic acid)-PoOPHM9 papers provided rapid colorimetric detection of malathion at 0.1-50 mM. The detection was completed within 5 min using a smartphone and image analysis software. As a proof-of-concept, malathion-contaminated water, plant, and apple samples were analyzed with the papers successfully. This material is promising for on-site rapid analysis of malathion-contaminated samples.

Biodegradation of Structurally Diverse Phthalate Esters by a Newly Identified Esterase with Catalytic Activity toward Di(2-ethylhexyl) Phthalate.

Herein, we report a double enzyme system to degrade 12 phthalate esters (PAEs), particularly bulky PAEs, such as the widely used bis(2-ethylhexyl) phthalate (DEHP), in a one-pot cascade process. A PAE-degrading bacterium, Gordonia sp. strain 5F, was isolated from soil polluted with plastic waste. From this strain, a novel esterase (GoEst15) and a mono(2-ethylhexyl) phthalate hydrolase (GoEstM1) were identified by homology-based cloning. GoEst15 showed broad substrate specificity, hydrolyzing DEHP and 10 other PAEs to monoalkyl phthalates, which were further degraded by GoEstM1 to phthalic acid. GoEst15 and GoEstM1 were heterologously coexpressed in Escherichia coli BL21 (DE3), which could then completely degrade 12 PAEs (5 mM), within 1 and 24 h for small and bulky substrates, respectively. To our knowledge, GoEst15 is the first DEHP hydrolase with a known protein sequence, which will enable protein engineering to enhance its catalytic performance in the future.

Efficient Degradation of Malathion in the Presence of Detergents Using an Engineered Organophosphorus Hydrolase Highly Expressed by Pichia pastoris without Methanol Induction.

The biodegradation of pesticides by organophosphorus hydrolases (OPHs) requires an efficient enzyme production technology in industry. Herein, a Pichia pastoris strain was constructed for the extracellular expression of PoOPHM9, an engineered malathion-degrading enzyme. After optimization, the maximum titer and yield of fermentation reached 50.8 kU/L and 4.1 gprotein/L after 3 days, with the highest space-time yield (STY) reported so far, 640 U L-1 h-1. PoOPHM9 displayed its high activity and stability in the presence of 0.1% (w/w) plant-derived detergent. Only 0.04 mg/mL enzyme could completely remove 0.15 mM malathion in aqueous solution within 20 min. Furthermore, 12 µmol malathion on apples and cucumbers surfaces was completely removed by 0.05 mg/mL PoOPHM9 in tap water after 35 min washing. The efficient production of the highly active PoOPHM9 has cleared a major barrier to biodegradation of pesticide residues in food industry.