Integrated Kinetic Modeling and Oxygen Transfer Analysis for Biosurfactant Production using Achromobacter xylosoxidans cultivated on Waste Lubricant Oil

Volumetric mass transfer coefficient (KLa), a numerical parameter in fermentation, is crucial for developing and scaling up bioprocesses, as it measures the rate of solute transfer from the gas phase to the liquid phase during fermentation. This parameter is essential for optimizing bioreactor design and operation. Additionally, precise kinetic modeling of bacterial growth and product formation are indispensable for scaling up production processes. In the present investigation, a biosurfactant-producing bacterium, Achromobacter xylosoxidans PSA5, was cultivated using waste lubricant oil (WLO) as the sole carbon source under varying oxygen concentrations. The modified Gompertz, Luedeking-Piret and firstorder kinetic models were employed to analyze the growth, biosurfactant production and WLO biodegradation. A specific growth rate of 0.0133 h-1 and surface tension reduction to 40 mN/m were observed at KLa of 16.29 hours-1 . The modified Gompertz model predicted growth and biosurfactant production (R² = 0.7 and 0.91). The Luedeking-Piret model indicated mixed-growthassociated biosurfactant production (α = 33.80, β = 0.1795). A first-order kinetic model effectively described WLO biodegradation (rate constant, k = 0.0053 hours−1, half-life = 130.8 hours and R² = 0.89). The model parameters revealed the rapid onset of biosurfactant production and its role in growth and promoting WLO biodegradation. The KLa values and kinetic parameters provide insights into the biosurfactant production dynamics, relating bacterial growth to effective WLO biodegradation. This approach illustrates the potential of these methods to advance sustainable biotechnological solutions in producing valuable bioproducts.