(23b) Enhancing D-Arabitol Production in Stirred-Tank Bioreactors: Comparative Evaluation of Rushton Turbine and Maxblend Impellers with Lignocellulosic Feedstocks

D-Arabitol, a multifunctional sugar alcohol with applications in food, pharmaceuticals, and biorefineries, faces production challenges due to high costs and byproduct formation in conventional fermentation systems. This study investigates the enhancement of D-arabitol production by Wickerhamomyces anomalus BKK11-4 through optimized bioreactor hydrodynamics and sustainable substrate utilization. We compared the performance of a traditional Rushton turbine (RT) impeller and an innovative Maxblend^® (MB) impeller across varying power inputs (1.5–4.5 kW/m³) and carbon sources: glucose, xylose, and sugarcane bagasse hydrolysate (CBT).

The RT impeller achieved a volumetric oxygen transfer coefficient (K_La) of 78 h⁻¹ at 4.5 kW/m³, driving a D-arabitol yield of 0.48 g/g on glucose. However, high power demand and glycerol coproduction (22 g/L) underscored inefficiencies. In contrast, the MB impeller delivered comparable K_La (75 h⁻¹) at 30% lower power input (3.2 kW/m³), reducing glycerol synthesis to 14 g/L while maintaining a D-arabitol titer of 45 g/L. This highlights MB’s superior energy efficiency and metabolic flux steering.

Substrate screening revealed CBT, containing 62 g/L glucose and 38 g/L xylose, as a viable lignocellulosic alternative. MB-mediated fermentation of CBT yielded 39 g/L D-arabitol with 85% xylose consumption, demonstrating the strain’s C5/C6 co-utilization capability. Elevated initial sugar concentrations (150 g/L) prompted osmotic stress adaptation, increasing intracellular arabitol accumulation by 40% but reducing extracellular productivity by 18%, necessitating trade-off optimization.

These findings establish MB impellers as a scalable solution for aerobic yeast fermentations, reducing operational costs while aligning with circular economy principles through sugarcane waste valorization. Future work will integrate real-time metabolic flux analysis to refine oxygen-sensitive pathway regulation.