NOVELTY - Use of an aqueous nutrient medium in non-sterile propagation of heterofermentative lactic acid bacteria, the medium containing buffers other than alkali acetate in an amount so that the pH of the medium at the start of a 2-stage growth of exclusively heterofermentative lactic acid bacteria with 10 to the power of 7/ml initial density is not below 4.5 at 24 degrees Centigrade.    USE - The method is for use of an aqueous nutrient medium in non-sterile propagation of heterofermentative lactic acid bacteria. The lactic acid bacterial culture is used as an ensilaging aid (e.g. for green fodder) (all claimed).    ADVANTAGE - A farmer is provided with a preparation of high initial bacterial density allowing achievement of high bacterial counts of ca. 10 to the power of 5 - 10 to the power of 6 in materials to be ensilaged. Most of the components used in the aqueous medium are at concentrations below those used in the medium of EP578912 and the heterofermentative lactic acid bacteria-based culture obtained is such that the aerobic stability of the silaging material is greater than when the culture of EP578912 is used.    DETAILED DESCRIPTION - Use of an aqueous nutrient medium in non-sterile propagation of heterofermentative lactic acid bacteria, the medium containing (based on water wt.) a monosaccharide (1 - 2 %), an alkali acetate (0.2 - 0.7 % acetate ions and acetic acid), nitrogen sources, trace elements, macroelements as well as buffers other than alkali acetate in an amount so that the pH of the medium at the start of a 2-stage growth of exclusively heterofermentative lactic acid bacteria with 10 to the power of 7/ml initial density is not below 4.5 at 24 degrees Centigrade.    An INDEPENDENT CLAIM is also included for a combined preparation for simultaneous propagation of homo- and hetero-fermentative lactic acid bacteria comprising:    (A) a dry nutrient medium which can be dissolved in water to give the aqueous nutrient medium; and    (B) heterofermentative lactic acid bacteria at 10 to the power of 5 - 10 to the power of 8 per g of (A).