A high temperature NADPH recycling system was designed utilizing a thermostable glucose-6-phosphate dehydrogenase (tG6PDH) from Bacillus stearothermophilus with glucose-6-sulfate (G6S) as the substrate. The thermostable alcohol dehydrogenase (tADH) from Thermoanaerobacter (formerly Thermoanaerobium) brockii was employed to catalyze the reduction of 2-butanone to 2-butanol at 55°C. It was established that the B. stearothermophilus G6PDH is capable of utilizing G6S as the substrate (KM=50mM at 55°C). NADPH recycling based on the G6S/tG6PDH system performed optimally with a 3:1 ratio of tG6PDH:tADH, and with 1mM NADP. The system produced 75mM 2-butanol and retained 60% of NADPH after 5h at 55°C. Under the same conditions, the system using glucose-6-phosphate (G6P), the natural substrate for tG6PDH, produced only 25mM 2-butanol and retained negligible amount of the co-factor.
- Alcohol dehydrogenase
- Glucose-6-phosphate dehydrogenase
- NADPH recycling
ASJC Scopus subject areas
- Process Chemistry and Technology