The invention relates to a new use of alpha-ketoglutarate for manufacturing of medical preparation for prophylaxis or treatment of undesired medical conditions associated with the presence and/or activity of ureolytic bacteria in living organisms, except plants, including a human being, pet and farm animal, such as mammal, bird, amphibian, fish, molluse or arthropod, whereas the undesired medical conditions is a condition associated with the presence and/or activity in the gastrointestinal tract, respiratory and/or urogenital system of ureolytic bacteria from the group including Helicobacter pylori, bacterial strains from the Brucella genus, urease-positive bacteria such as Ureaplasma ureolyticum and other alkalophilic bacteria, such as for instance Bacillus pasteurii, urease-producing Yersinia enterocolica rods, ureolytic bacteria that participate in the formation of biofilm and mineralisation of deposits on catheters and other medical equipment, ureolytic bacteria causing infections of the mucous membrane in the oral cavity, gingival diseases, dental caries, causing formation of tartar, ureolytic bacteria responsible for formation of infectious stones in course of urinary system infections of the genii: Proteus, Ureaplasma, Klebsiella, Pseudomonas, Staphylococcus, Providencia, Corynebacterium, in particular P. mirabilis, and mycoplasmas causing genital tract--in particular its lower part infections, Mycoplasma hominis and U. urealyticum. The invention also covers new medical preparations, dietary supplements, special medicated food and food/feed additives containing alpha-ketoglutarate, useful in prophylaxis and inhibition of colonisation of living organisms, except plants, including a human being, pet and farm animal, such as mammal, bird, amphibian, fish, molluse or arthropod, by harmful ureolytic bacteria, in particular organisms of human beings and domestic animals by H. pylori. Moreover, according to the invention alpha-ketoglutarate is used as an active ingredient in methods of prophylaxis and treatment of the a.m. diseases and conditions associated with ureolytic bacteria, as well as in a process for the manufacture of organic biofuel, based on the conversion of biomass comprising of lignin and cellulose by means of bacterial enzymes, wherein the enzymes produced by hindgut ureolytic microbiota of wood-feeing higher termites are used in presence of alpha-ketoglutarate.