NOVELTY - Transesterifying triglycerides present in biodiesel feedstock (203) with methanol, comprises e.g.: (a) passing filtered and dried biodiesel feedstock through guard bed ion-exchange column; (b) contacting at temperature of less than 102 degrees F, a methanol, a solid heterogeneous transesterification enzyme catalyst immobilized on a solid support, and biodiesel feedstock, where contacting is carried to provide transesterification reaction product comprising biodiesel, methanol, water, glycerin and optionally triglycerides; and (c) separating water, glycerin and methanol from reaction product.    USE - The method is useful for transesterifying triglycerides present in a biodiesel feedstock with methanol which is useful to produce biodiesel and glycerin from biodiesel feedstock (all claimed).    ADVANTAGE - The method: separates the biodiesel from the glycerin, and thus the purified biodiesel has less than 2000 ppmw of methanol, not greater than 0.12 wt.% of total glycerol, not greater than 200 ppmw of free glycerin and not greater than 0.2 acid number, and has a flash point of at least 170 degrees C, moisture content of not greater than 50 ppmw, a sulfur content of less than 5 ppm, phosphorus content of less than 5 ppm, polymerized triglycerides content of less than 5 ppm and a sterols content of less than 10 ppm; converts at least 90 wt.% of the triglycerides present in the biodiesel feedstock to biodiesel; and is carried out in the absence of sodium methylate and a mineral acid (claimed), where absence of sodium methylate avoids saponification issues and achieves biodiesel-glycerin separation, higher glycerin purity and high yields, and absence of a mineral acid avoids higher operating cost and disposal issues.    DETAILED DESCRIPTION - Transesterifying triglycerides present in a biodiesel feedstock (203) with methanol, comprises: (a) passing a filtered and dried biodiesel feedstock through a guard bed ion-exchange column, to remove undesired components; (b) contacting at a temperature of less than 102 degrees F a methanol, a solid heterogeneous transesterification enzyme catalyst immobilized on a solid support, and a biodiesel feedstock comprising triglycerides, where contacting is carried out under conditions suitable to provide a transesterification reaction product comprising biodiesel, methanol, water, glycerin and optionally triglycerides; (c) separating water, glycerin and methanol from the transesterification reaction product; (d) contacting the transesterification reaction product with methanol and a solid heterogeneous transesterification enzyme catalyst immobilized on the solid support, where the contacting is carried out under conditions suitable to provide a subsequent transesterification reaction product comprising biodiesel, methanol, water, glycerin and optionally triglycerides; and (e) separating water and methanol from the subsequent transesterification reaction product, where the methanol that is separated from at least one transesterification reaction product is purified to a purity of at least 99.9 wt.%, and is employed in a subsequent transesterification.    DESCRIPTION OF DRAWING(S) - The figure illustrates a process flow diagram for the esterification of free fatty acids.    Biodiesel feedstock (203)    Mixture of methanol and water (211)    Water (219)    Methanol (221)    Purified methanol (223)