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Kinetic analysis of central metabolic regulation in Debaryomyces hansenii for enhanced xylitol and ethanol production from oil palm empty fruit bunches
Bani A.
Chemical Engineering Communications
Q2Abstract
This study investigates the intracellular metabolism of Debaryomyces hansenii, a yeast capable of producing xylitol and ethanol from xylose and glucose derived from the pretreatment of lignocellulosic biomass, specifically oil palm empty fruit bunches. The metabolic model comprises 14 intracellular metabolites and 14 enzymatic reactions, capturing glycolysis and the pentose phosphate pathway as the main pathways of sugar conversion. By combining a kinetic model with metabolic control analysis, a sensitivity analysis was conducted to evaluate the influence of system parameters. Elasticity coefficients were used to assess local responsiveness, while control coefficients quantified the global impact of individual reactions on product formation. The analysis revealed that substrate uptake from hemicellulose and cellulose exert the strongest positive control on xylitol and ethanol concentrations. In contrast, xylitol dehydrogenase showed the most significant negative control on xylitol production, while pyruvate dehydrogenase exhibited the highest negative control on ethanol concentration. To enhance product yields, several regulatory strategies were simulated using an optimal control approach. The most effective approach involves increasing substrate uptake rates and reducing the maximum catalytic activity of pyruvate dehydrogenase by ∼40%. This combined regulation significantly increased the product concentrations compared to the unoptimized conditions: xylitol increased by 67.03% (∼1.67-fold) and ethanol increased by 174.84% (∼2.75-fold). These findings provide strategic insights for optimizing microbial production using lignocellulosic feedstocks.