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 Fe³⁺. 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. [ABSTRACT FROM AUTHOR]