TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The reactor is a separator for separating fat, oil, monoglyceride, diglyceride and/or alcohol containing fraction in downstream. The separator exhibits at least an outlet for the fraction containing the fat, oil and/or alcohol, and which is connected to the mixing unit via an inlet. The separator is a distillative separator, a membrane separator, a crystallization separator, an adsorption separator or an extraction separator. The reactor is an agitating reactor or a solid bed reactor.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation (Claimed): Preparation of the biofuel mixture comprises partial transesterification of triglycerides under the addition of an alcohol.Preferred Composition: The biofuel contains 3-10 wt.% of the bounded glycerin fraction and greater than 50 (preferably 80) wt.% of the fatty acid alkyl ester fraction. In the biofuel, a portion of fats and/or oils is dissolved; a portion of less than 10 wt.% of residue fat and/or residue oil is dissolved and a portion of monovalent alcohol is dissolved. The bio fuel mixture is mixed with a mineralic fuel or a biofuel.Preferred Process: During the partial transesterification, pure fat or oil is reacted with mono- and/or bivalent alcohol followed by addition of catalysts, in the reaction, to cleave fatty acid until a mixture of fatty acid alkyl ester and at least a monoglyceride and/or diglycerides and additionally triglyceride is obtained in a specific ratio as reaction products.The ratio of the reaction products is adjusted over a retention time, during the contacting step of fat or oil with mono- and/or bivalent alcohol and the catalyst. The ratio of the reaction products is adjusted by the quantity of mono- and/or bivalent alcohol that are reacted with the fat and/or oil or adjusted by the type and/or the quantity of the catalyst. During the preparation, a step of dehydration is carried out before and/or during the partial transesterification. In the preparation method, fatty acid alkyl ester is provided and by addition of monoglycerides and/or diglycerides, a mixture from the fatty acid alkyl ester and the monoglycerides and/or diglycerides is formed.To the mixture, a monovalent and/or polyvalent alcohol and bounded glycerin are added.Preferred Components: In the method, one or more regiospecific lipase or one or more nonspecific catalysts and/or nonspecific enzymes are used as the catalyst. The catalyst is bound on a carrier. EXAMPLE - Methanol (3.5 g) and sn-1-3 regiospecific lipase were added to vegetable oil (100 g). The mixture was thoroughly mixed for 9 hours at the temperature with the highest lipase activity. After 9 hours, methanol (3.5 g) was added again. The reaction mixture was stirred for 15 hours at the optimal lipase temperature, to form a clear solution containing monoglycerides, diglycerides, fatty acid alkyl ester and plant oil dissolved in less wt.% of methanol.