The aim of the study was to evaluate the impact of bacterial preparation, containing strains of Lactobacillus genera that stimulate the synthesis of 1,2-propanediol and carboxylic acids of low molecular weight, on aerobic stability of meadow sward silages and biogas yield by means of heterofermentation. Lactobacillus buchneri, L. diolivorans and L. reuteri, which are synergistically active in the synthesis of acetic acid and products of its metabolism: 1,2-propanediol and propionic acid, have been selected in the earlier studies and their co-fermentation conditions have been determined. The composition of the Lactosil Biogas starter culture was designed to conserve renewable raw materials, including meadow grass, for the production of biogas. The preparation was used for ensiling on the production scale. Based on the results of the silage analysis it was found that the action of starter culture of the new bacterial preparation resulted in an increase in acetic acid, 1,2-propanediol and propionic acid content in experimental silages and prolongation of their aerobic stability against control silages during three months of ensiling. The application of the Lactosil Biogas to the meadow grass resulted in an increase in biogas yield of the silage, processed in methane fermentation of the plant material, by 39.9 NI kg dry organic matter-1, while increasing the content of methane by 3.7% and reducing the biogas contaminants.