BACKGROUND
2,3‐Butanediol (2,3‐BD) has a wide range of applications in chiral molecular synthesis, biofuel additives, and in food flavor additive manufacturing. Fermentation is a favorable method for 2,3‐BD production. However, it requires much time and produces several NADH related byproducts which compete with 2,3‐BD production. Bacillus subtilis has an excellent ability for 2,3‐BD production by biocatalysis. However, its production is limited by low intracellular NADH and the reversible property of acetoin reductase (AR/2,3‐BDH). The whole cell biocatalyst process with two different NADH regeneration systems was designed for efficient production of 2,3‐BD in B. subtilis 168.
RESULTS
Formate dehydrogenase and glucose dehydrogenase for NADH regeneration were successfully co‐expressed with acetoin reductase in B. subtilis 168. After optimization of biocatalyst bioconversion conditions, B. subtilis 168/pMA5‐bdhA‐HpaII‐fdh yielded 74.5 g L−1 of 2, 3‐BD with 9.3 g L−1 h−1 productivity by fed batch and 115.4 g of 2,3‐BD was achieved using same batch bacterium by three repeated batch bioconversions. On the other hand, 63.7 g L−1 of 2, 3‐BD was produced with 7.92 g L−1 h−1 productivity by B. subtilis 168/pMA5‐bdhA‐HpaII‐gdh. To our knowledge, the volume productivity obtained here is the highest ever reported for biocatalysis.
CONCLUSION
A higher productivity of 2,3‐BD from acetoin was achieved by whole cell biocatalysis with NADH regeneration systems in B. subtilis 168. This approach can be applied for NADH related bio‐based chemicals production to improve titer, yield and productivity. © 2017 Society of Chemical Industry