Enzymatic Cascades for Efficient Biotransformation of Racemic Lactate Derived from Corn Steep Water

The corn starch industry produces a large amount of corn steep water, leading to high organic waste load. Lactate could be separated from corn steep water at a low cost, which supports the value-added utilization of corn steep water. However, the racemic characteristic of lactate from corn steep water restricts the development of this promising process. In this study, using d-lactate oxidase (d-LOX) from Gluconobacter oxydans, l-lactate oxidase (l-LOX) from Pediococcus sp., pyruvate decarboxylase from Zymomonas mobilis, and catalase from bovine liver, we synthesized an in vitro enzymatic system, including different enzymatic cascades, for the production of valuable platform chemicals from lactate separated from the corn steep water. Pyruvate was produced as an important intermediate and further converted into C2 (acetaldehyde) and C4 (acetoin) platform chemicals at high yields using optimized concentrations of pyruvate decarboxylase. The in vitro enzymatic system not only provides a novel technology platform for the production of optical lactate and lactate derivatives but also supports the sustainable development of corn starch industry.