Enhancing catalytic efficiency of a salt-induced Neurospora crassa xylose reductase for xylitol bioprocesses

Xylitol is a sugar alcohol widely used in the food industry due to its lower caloric value compared to sucrose. Industrial xylitol production relies primarily on chemical hydrogenation processes that require high energy input. Although biotechnological routes represent a more sustainable alternative, their industrial implementation is often limited by enzyme stability and cofactor costs. This study presents the design, expression, and biochemical analysis of recombinant xylose reductase from Neurospora crassa (rNcXR). The optimized gene was cloned into a salt-inducible T7-based expression system and expressed in Escherichia coli BL21-SI. The design incorporated an OmpT signal peptide to encourage secretion into the periplasm, and a 6×His tag at the C-terminus to simplify purification. The recombinant enzyme exhibited a specific activity of 13.93 U/mg, exceeding values previously reported for native and recombinant xylose reductases. rNcXR displayed high stability over a temperature range of 25–45°C and retained significant activity at elevated temperatures. These results demonstrate that the engineered rNcXR represents a robust and efficient biocatalyst with strong potential for enzymatic xylitol production.