The fundamental mechanism of early attachment between Chlorella vulgaris microalgae cells and polyurethane foam support material was unveiled prior to the kinetic study and optimization of operational bed packing volume in fluidized bed bioreactor. All aiming to enhance the lipid accumulation for sustainable biodiesel production. The two-step early attachment mechanism was found starting with the short-range Lewis acid-base interaction before the cells migrating toward the surface of support material induced by the electrostatic attractive force. This mechanism was mainly propelled by the chemisorption stemming from the interactions of cell-to-cell repulsion and cell-to-support material attraction. The electrostatic attractive interaction transpired on the surface of support material was also maneuvering the kinetics of formation of early attachment as reflected by the zeta potential trend via the sequence of pH 9 < pH 7 < pH 5 > pH 3. The rapid early attachment formation in pH 5 culture medium in fluidized bed bioreactor had led to the highest weight of attached growth microalgae biomass attainability as opposed to the other pH mediums. By exploiting the pH 5 culture medium, the maximum yields of microalgae biomass, lipid and later biodiesel were harvested from the bioreactor packed with 6% (v/v) of polyurethane foam support material, confirming optimum packing volume. These yields were initially observed increasing with the increase of packing volume due to the increasing surface area of support material; and unfortunately, decreasing after 6% (v/v) of packing volume due to the congestion factor.
