NOVELTY - Method of preparing a nutrient base for microbiological media relates to biotechnology. The method is intended for producing a base for preparing microbiological culture media from marine raw material and can be used in medicine and industrial microbiology, scientific research and practical work for separating and culturing microorganisms. The method includes preparation of alkaline hydrolysate from shellfish and merging with an acid hydrolysate of fish material in ratio of 1:3-3:1 so that the amount of amine nitrogen is in the range of 600-900 mg%. Hydrolysis of the homogenate of fish material is carried out in an acidic medium. When preparing the acid hydrolysate from fish material, the homogenate of fish material is mixed with 18-20% hydrochloric acid solution to achieve pH 4.5-5.0 and heated to 45-50 degrees C for 22-26 hours, followed by addition of concentrated orthophosphoric acid to achieve residual acid concentration of 2% and heating the homogenate of fish material at 100 degrees C for 22-26 hours and then neutralising the hydrolysate of fish material by adding 40% sodium hydroxide solution to achieve pH 6.8-7.4. When preparing the alkaline hydrolysate from shellfish, 1.0% sodium hydroxide solution is added to the crushed shellfish material in ratio of 1:1 and hydrolysis is carried out at 80 degrees C for 20-24 hours. The shellfish hydrolysate is then neutralised by adding concentrated hydrochloric acid to achieve pH 6.8-7.4. Hydrolysis of the shellfish material is carried out to obtain an amount of amine nitrogen in the range of 240-450 mg%. The acid hydrolysate of fish material is mixed with the alkaline hydrolysate of shellfish before neutralisation of the hydrolysate of fish material with subsequent adjustment of acidity of the biomass to pH 6.8-7.4. Acidity of the obtained base for microbiological culture media is adjusted to pH 7.0.    USE - Biotechnology.    ADVANTAGE - Wider raw material base and improved environmental friendliness of production.