The application concerns a consortium of microorganisms capable of hydrolyzing proteins and fats, which is advantageous in the disposal of sewage sludge and/or the biodegradation of hardly degradable organic compounds in contaminated soils. It comprises the following mixtures of bacterial strains: Stenotrophomonas sp. POC 10, Klebsiella sp. POC 16, Brevundimonas sp. POC 21, Bacillus sp. PSUB 1 (mixture deposited at PCM under deposit number B/00087); and Bacillus sp. PSUB 9, Bacillus sp. LPMIX 2, Brevundimonas sp. LPMIX 5 (mixture deposited at PCM under deposit number B/00088); and Brevibacterium sp. LPMIX 6, Bacillus sp. LPSUB 4, Micrococcus sp. LPSUB 9 (mixture deposited at PCM under deposit number B/00089); and Staphylococcus sp. PGN 1, Solibacillus sp. LPSUB 13, Lysinibacillus sp. LPSUB 15 (mixture deposited at PCM under deposit number B/00090); and Bacillus sp. PMIX 8, Bacillus sp. LPOC 3, Ochrobactrum sp. POC 9, Rummeliibacillus sp. POC 4 (mixture deposited at PCM under deposit number B/00091). The application also pertains to a preparation for the hydrolysis of proteins and fats comprising this consortium, as well as its use for the disposal of sewage sludge and/or the biodegradation of hardly degradable organic compounds in contaminated soils, and a method utilizing them.