Efficient acetoin production from pyruvate by engineered Halomonas bluephagenesis whole-cell biocatalysis

Acetoin is an important platform chemical, which has a wide range of applications in many industries. Halomonas bluephagenesis, a chassis for next generation of industrial biotechnology, has advantages of fast growth and high tolerance to organic acid salts and alkaline environment. Here, α-acetolactate synthase and α-acetolactate decarboxylase from Bacillus subtilis 168 were co-expressed in H. bluephagenesis to produce acetoin from pyruvate. After reaction condition optimization and further increase of α-acetolactate decarboxylase expression, acetoin production and yield were significantly enhanced to 223.4 mmol·L⁻¹ and 0.491 mol·mol⁻¹ from 125.4 mmol·L⁻¹ and 0.333 mol·mol⁻¹, respectively. Finally, the highest titer of 974.3 mmol·L⁻¹ (85.84 g·L⁻¹) of acetoin was accumulated from 2143.4 mmol·L⁻¹ (188.6 g·L⁻¹) of pyruvic acid within 8 h in fed-batch bioconversion under optimal reaction conditions. Moreover, the reusability of the cell catalysis was also tested, and the result illustrated that the whole-cell catalysis obtained 433.3, 440.2, 379.0, 442.8 and 339.4 mmol·L⁻¹ (38.2, 38.8, 33.4, 39.0 and 29.9 g·L⁻¹) acetoin in five repeated cycles under the same conditions. This work therefore provided an efficient H. bluephagenesis whole-cell catalysis with a broad development prospect in biosynthesis of acetoin.