Xian-Lin Wang's research while affiliated with Zhejiang University of Technology and other places

R-2-(4-hydroxyphenoxy)propionic acid (R-HPPA) is a key intermediate for the synthesis of classic herbicides with high selectivity against grassy weed. The main route for R-HPPA biosynthesis is to hydroxylate the substrate R-2-phenoxypropionic acid (R-PPA) at C-4 position with microbes. In order to provide sufficient R-PPA for the industrial production of R-HPPA, an effective R-PPA synthesis method was established and optimized in this work. The synthesis process mainly consisted of two steps: (1) synthesis of S-2-chloropropionic acid from L-alanine via diazotization and chlorination reactions; and (2) synthesis of R-PPA from S-2-chloropropionic acid and phenol via etherification reaction. The optimal reaction conditions were as follows: HCl: NaNO2: KI: L-Ala = 2.0: 1.2: 0.7: 1.0 (in molar), 125 °C reflux for 1.5 h, with KI as catalyst, and KI: S-2-chloropropionic acid: phenol = 0.075: 1.2: 1.0 (in molar). Under these conditions, an improved molar conversion rate (74.9%, caculated in phenol) was achieved. After extraction using anionic exchange resin Amberlite IRA-400 (CI), R-PPA product with a purity of 95.08% was obtained. The purified R-PPA was identified and evaluated in the application of the biotransformative production of R-HPPA. The results indicated that the synthesized R-PPA supported the R-HPPA biosynthesis with a comparable yield as that of the standard R-PPA. The R-PPA synthesis method provided herein exhibited the advantages of low price and easy availability of raw materials, less toxicity of reagents, simple manipulations, and low equipment/instrument requirements.

(R)-2-(4-hydroxyphenoxy)propionic acid (HPOPA) is a key intermediate for the preparation of aryloxyphenoxypropionic acid herbicides (R-isomer). In order to improve the HPOPA production from the substrate (R)-2-phenoxypropionic acid (POPA) with Beauveria bassiana CCN-A7, static cultivation and H2O2 addition were attempted and found to be conducive to HPOPA production. It was the first report on HPOPA production under static cultivation and reactive oxygen species (ROS) induction. In this premise, the cultivation conditions and fermentation medium compositions were optimized. As a result, the optimal carbon source, organic nitrogen source, and inorganic nitrogen source were determined to be glucose, peptone, and ammonium sulfate, respectively. The optimal inoculum size and fermentation temperature were 13.3% and 28°C, respectively. The significant factors including glucose, peptone, and H2O2, identified based on Plackett-Burman design, were further optimized through Central Composite Design (CCD). The optimal concentrations/amounts were as follows: glucose 38.81 g/L, peptone 7.28 g/L, and H2O2 1.08 mL/100 mL. Under the optimized conditions, HPOPA titer was improved from 9.6 g/L to 19.53 g/L, representing an increase of 2.03-fold. The results obtained in this work will provide novel strategies for improving the hydroxy aromatics biosynthesis.

R-2-(4-hydroxyphenoxy)propionic acid (R-HPPA) is a key chiral intermediate for phenoxypropionic acid herbicide synthesis. In this study, to improve the production of R-HPPA with B. bassiana ZJB16007, the cultivation conditions in solid-state fermentation (SSF) were investigated. The effects of various substrates on R-HPPA production were evaluated and the process parameters were also optimized. The results showed that rice bran was the optimal substrate for R-HPPA production. The optimal medium components and cultivation conditions were: rice bran: silkworm chrysalis powder = 5.25: 2.25 (g: g), nutrient salts solution 12 mL which contained 50 g/L R-PPA, pH 5.0, and cultivated at 28 °C for 11 days. Under the optimized conditions, the transformation of R-HPPA was significantly improved and the yield of R-HPPA reached 77.78%, which was 15.14% higher than that of the control (67.55%). Therefore, SSF may serve as an alternative for R-HPPA production by B. bassiana ZJB16007.