Solid-supported microorganism of Burkholderia cenocepacia cultured via solid state fermentation for biodiesel production: Optimization and kinetics

The objectives of this work were to investigate the optimization and kinetics of ethanolysis for biodiesel production by solid-supported microorganism of Burkholderia cenocepacia cultured via solid state fermentation (SSF). Operational parameters affecting the biodiesel yield were successively optimized by Plackett-Burman design followed with Box-Behnken method. The biodiesel yield of ca. 91.3% was verified under the optimized conditions of 4.3:1 of alcohol/oil molar ratio, 1.63 g/mL of solid-supported microorganism mass, 4.6% (wt/wt) of water and 44.2 °C of temperature. Furthermore, the kinetic model was developed on the basis of Ping Pong Bi Bi mechanism with competitive alcohol inhibition. The proposed model had a satisfactory correlation coefficient of R2 = 97.60%, and kinetic parameters of vmax = 3.88 mmol/(L min), KmTG=0.27mmol/L, KmC2H5OH=4.03mmol/L, and Ki = 0.34 mmol/L were obtained. In addition, the calculated activation energy (Ea) of the biocatalyst was estimated to be 37.95 kJ/mol. The rate-limiting reaction step for the ethanolysis by solid-supported microorganism in tert-butanol was demonstrated to be the conversion of di-glyceride to mono-glyceride. Finally, the reusability of the solid-supported microorganism was evaluated in successive batch reactions and presented 66.9% of original activity after 288 h repeated usage.