Identification of a Novel Alditol Oxidase from Thermopolyspora flexuosa with Potential Application in d -Glyceric Acid Production

Glycerol is a potential sustainable feedstock, and biorefining processes to convert glycerol into value-added chemicals have been developed over the past decade. Alditol oxidase (AldO) is capable of selectively oxidizing the primary hydroxyl groups of alditols such as glycerol. In this study, a new FAD-binding protein from Thermopolyspora flexuosa was expressed and identified as a novel alditol oxidase (AldO T. fle ). AldO T. fle displayed the optimal activity at pH 8.0 and 25 °C. AldO T. fle was not metal-dependent, but the activity was completely inhibited by Fe 3+ . AldO T. fle had a wide substrate specificity and high catalytic efficiency for glycerol. Furthermore, the recombinant AldO T. fle could produce d -glyceric acid from glycerol with a conversion rate ranging from 86.6% (5 mM glycerol) to 20.5% (500 mM glycerol). The recombinant E. coli with AldO T. fle could also produce 23.8 mM d -glyceric acid from 100 mM glycerol. The recombinant AldO T. fle had the potential to produce other aldehyde products by selectively oxidizing the hydroxyl groups of alditols and many other commodity chemicals by redesigning glycerol metabolism.