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Kaempferol and quercetin possess various biological activities, making them valuable in food and medicine. However, their production via traditional methods is often inefficient. This study aims to address this gap by engineering the yeast Yarrowia lipolytica to achieve high yields of these flavonoids. We designed a kaempferol biosynthetic pathway by integrating multiple-copy fusion enzyme expression modules, F3H-(GGGGS)2-FLS, into the genome with an optimized linker (GGGGS)2 to enhance kaempferol production from naringenin. To synthesize quercetin de novo, we introduced the FMOCPR gene into the kaempferol-synthesizing strain using the optimized pFBAin promoter. Notably, increasing glucose concentration effectively boosted the production of both flavonoids. Our results demonstrated kaempferol and quercetin titers reaching 194.30 ± 7.69 and 278.92 ± 11.58 mg/L, respectively, in shake-flask cultures. These findings suggest that Y. lipolytica is a promising platform for the efficient production of flavonoid-derived products. [ABSTRACT FROM AUTHOR]

It is a green and economical route to synthesize levodopa by enzyme catalysis instead of chemical methods. The coding gene of tyrosine phenol- lyase derived from Citrobacter freundii was ligated to pKK223- 3 vector to construct the expression vector pKK223- TPL. The pKK223- TPL was successfully expressed in Escherichia coli BL21 ( DE3) . The key factors on tyrosine phenol- lyase activity and stability were studied, and the catalytic conditions for reducing the formation of by- products and increasing the substrate conversion were explored. After optimization, by- products were reduced and the stability of tyrosine phenol- lyase was improved, under the conditions of pH 7. 5, 20 °C, catechol 12 g /L, sodium pyruvate ≥7. 5 g /L, 0. 4 mol /L ammonium acetate as the ammonia source, and 0. 1 mmol /L K+ as the activator. After 12 hours of reaction, the yield of levodopa reached 122. 8 g /L, and a maximum conversion rate of catechol reached 98. 7%, which is superior to that repored so far, indicating a great industrial potential. [ABSTRACT FROM AUTHOR]

N-Acylhomoserine lactonase degrades the lactone ring of N-acylhomoserine lactones (AHLs) and has been widely suggested as a promising candidate for use in bacterial disease control. While a number of AHL lactonases have been characterized, none of them has been developed as a commercially available enzymatic product for in vitro AHL quenching due to their low stability. In this study, a highly stable AHL lactonase (AhlX) was identified and isolated from the marine bacterium Salinicola salaria MCCC1A01339. AhlX is encoded by a 768-bp gene and has a predicted molecular mass of 29 kDa. The enzyme retained approximately 97% activity after incubating at 25 °C for 12 days and ~100% activity after incubating at 60 °C for 2 h. Furthermore, AhlX exhibited a high salt tolerance, retaining approximately 60% of its activity observed in the presence of 25% NaCl. In addition, an AhlX powder made by an industrial spray-drying process attenuated Erwinia carotovora infection. These results suggest that AhlX has great potential for use as an in vitro preventive and therapeutic agent for bacterial diseases. [ABSTRACT FROM AUTHOR]

A method was developed for the determination of the content of aminobutanol by high performance liquid chromatography (HPLC) based on charge transfer reaction. Under the condition of a borax-boric acid buffer solution of pH 8.4, aminobutanol and tetra-chloro-benzoquinone reacted at 60℃ for 60 min, and were analyzed by an HPLC-ultraviolet detector. The charge-transfer complex was separated on an Agilent Extend C18 column (250 mm×4.6 mm, 5 μm) with 0.001% (v/v) triethylamine and methanol as the mobile phases for gradient elution at a flow rate of 1 mL/min. The limit of quantification of aminobutanol was 0.01 g/L, the linear range was 0.1-0.6 g/L, and the correlation coefficient ( R 2 ) was 0.9994. The spiked recoveries of the method were 98.3%-103.6% with relative standard deviations (RSDs) of 0.9%-1.6%. The method is simple and quick, and suitable for the rapid detection of aminobutanol.