Efficient biosynthesis of 3, 4-dihydroxyphenylacetic acid in Escherichia coli.

3, 4-Dihydroxyphenylacetic acid (3, 4-DHPA) is a phenolic acid with strong anti-oxidative activity, showing potential applications in food and pharmaceutical industries. In this study, a 3, 4-DHPA biosynthetic pathway was designed by connecting 4-hydroxyphenylacetic acid (4-HPA) biosynthesis with its hydroxylation. The starting strain produced only 46 mg/L of 4-HPA in 48 h. Enhancing the shikimate pathway increased the titer by 19-fold to 923 ± 57 mg/L. Furthermore, pykA and pykF were disrupted to conserve phosphoenolpyruvate for 4-HPA production. With this effort, 4-HPA titer was increased to 1817 ± 55 mg/L. Introducing the hydroxylase HpaBC into the 4-HPA overproducing strain resulted in 3, 4-DHPA production and the best strain produced 1856 ± 67 mg/L of 3, 4-DHPA in shake flask cultures. This work reports de novo biosynthesis of 3, 4-DHPA for the first time and provides a promising alternative for sustainable production of this valuable compound.

Improvement of Trehalose Production by Immobilized Trehalose Synthase from Thermus thermophilus HB27.

Trehalose is a non-reducing disaccharide with a wide range of applications in the fields of food, cosmetics, and pharmaceuticals. In this study, trehalose synthase derived from Thermus thermophilus HB27 (TtTreS) was immobilized on silicalite-1-based material for trehalose production. The activity and the stability of TtTreS against pH and temperature were significantly improved by immobilization. Enzyme immobilization also led to a lower concentration of byproduct glucose, which reduces byproduct inhibition of TtTreS. The immobilized TtTreS still retained 81% of its initial trehalose yield after 22 cycles of enzymatic reactions. The immobilized TtTreS exhibited high operational stability and remarkable reusability, indicating that it is promising for industrial applications.