Enzymes are renewable. They can be cultivated from bacteria and fungi and be mass-produced. Enzymatic reactions typically have the characteristics shown in Table 11.1.

The enzymatic process is intrinsically “green,” especially in comparison with the chemical process. It can be applied to simultaneously convert both neutral oil

and FFA. Applying enzyme catalysts for biodiesel production has long been rec­ognized as a better approach to biofuel production. However, full development and successful application of enzymatic biodiesel technology are hampered by poisoning of the catalyst, which in turn leads to high costs and inefficient opera­tions. Poisoning or deactivation of the catalyst is due to methanol, ethanol and most especially glycerol. This problem has long puzzled scientists and research­ers, and the solution has not been known until the use of the right inert solvent in the reaction [ET Process®, patented worldwide, Sunho Biodiesel Corporation (SBC)] was discovered. Figure 11.1 shows the deactivation effect from glycerol droplets when inert solvent is slightly insufficient for a column reaction. Glycerol deactivation is independent of whether the operation is performed with a packed bed reactor or a CSTR. Without an inert solvent, the activity of the enzyme will gradually decrease within a period of time.