Abstract: The present invention describes bacterial strains CECT 7968, CECT 7969 and NCIMB 42026 of the species B. subtilis, capable of expressing the heterologous synthetic mutated genes: pdc and adhB, originating from Z. mobilis, 'tesA, originating from E. coli, and atfl, originating from Acinetobacter sp. ADP1. Furthermore, said strains may overexpress at least one of the genes of the ACC (acetyl-CoA carboxylase) and acyl-CoA synthetase enzymatic complexes. The use of said strains produces an increase in the production of biofuel, preferably biodiesel from glycerin as the carbon source. Moreover, the present invention describes the use of said bacterial strains for the production of said biofuel, biodiesel, from glycerin, as well as a process for synthesising biofuel, preferably biodiesel, using the strains described in the present invention and the biofuel duly obtained.