Biodiesel production using magnetic whole-cell biocatalysts by immobilization of Pseudomonas mendocina on Fe3O4-chitosan microspheres

• First report on Pseudomonas mendocina containing MWCBs for lipid conversion.
• A biodiesel yield of 87.32% was achieved at optimized conditions within 48 h.
• MWCBs prepared can be reused for 10 cycles with retaining 83.57% yield.
• Kinetic data followed Michaelis-Menten model with methanol competitive inhibition.

Magnetic whole-cell biocatalysts (MWCBs) for enzymatic biodiesel production from soybean oil were constructed by immobilizing Pseudomonas mendocina cells into Fe3O4-chitosan microspheres. The effects of the MWCBs concentration, temperature, the molar ratio of methanol to oil and water content on biodiesel yield were studied. For the MWCBs, a biodiesel yield of 87.32% was obtained under the optimum operating condition (MWCBs concentration of 10 wt.%, water content of 10 wt.%, 35 °C, methanol to oil molar ratio of 4:1 and a four-step addition of methanol) for 48 h. The kinetic data followed Michaelis-Menten model (rmax, 2.1801 mg/min; Km, 0.4272 mg/mL; KI, 0.2308 mg/mL) with competitive inhibition by methanol. MWCBs had an excellent reusability and still gave a biodiesel yield of 83.57% after 10 cycles, which was higher than that of Fe3O4-uncontained whole cell biocatalysts (74.06%). Moreover, MWCBs could be separated and be recycled easily due to their superparamagnetism. Therefore, MWCBs would be promising for large-scale biodiesel industry.

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