Protein deficiency in animal rations determines a sharp increase in demand of fodder and feed additives containing non-conventional protein sources of animal and plant origin. The most attractive solution of the problem is development of resource-saving and wasteless technologies of producing feed protein from vegetable processing residues, e.g. cakes of oil seed cultures. Microbial and microbial-enzymatic fermentation can significantly improve the nutritive value, assimilation and flavor of the end product by enriching its protein content and decreasing the ratio of hardly digestible ingredients. Earlier bacterial strain ST-4 actively utilizing soybean cake components as sources of energy and nutrition was isolated from grain of cereal crops. Aim of this paper was investigation of cultural-morphological and physiological-biochemical characteristics of strain ST-4, its preliminary identification and assessment of application prospects for manufacturing protein-upgraded feed product derived from fermentation of soybean cake. Bacterial culture was grown on meat-peptone agar medium at 27–29°C for 72 h and maintained at 8–10°C by regular transfers. Preliminary identification of microbial strain was based on cultural-morphological and physiological-biochemical properties. Fermentation of soybean cake, after soaking with tap water, was carried out at temperature 20–32°C during 12–72 h using aqueous suspension of bacterial cells grown under above-mentioned conditions. The fermentation product was dried by convection technique at 50°C until residual moisture content ≤10%. Microbiological, biochemical and physical properties of intact and fermented soybean cake were established by generally recognized methods. The experiments were performed in triplicate. Statistical processing of the obtained data was performed using software from Microsoft Office Excel 2010 package. Based on analysis of cultural-morphological and physiological-biochemical peculiarities, the isolate ST-4 was referred to bacteria of genus Paenibacillus. The tests performed on laboratory animals revealed that this culture did not display pathogenic, allergenic and toxigenic action. Fermentation of soybean cake by Paenibacillus sp. strain ST-4 resulted in synthesis of extracellular enzyme complex involved in depolymerization of substrate constituents – xylan, glucan, cellulose, phytate, starch, lipids, pectins, proteins. Conditions favoring fermentation of soybean cake by Paenibacillus sp. strain ST-4 were defined, allowing it to increase crude protein content in the end product at least by 6.2 %. The study was conducted in the independent accredited laboratory to evaluate quality of native and fermented soybean cake in the course of scale-up process under optimized conditions. The analysis of product composition has shown that microbial treatment of soybean cake enhanced concentration of crude protein by 11.3 % (including amino acid content by 9.1 %) and diminished crude fiber ratio by 39.5 %. Moreover, the analysis did not reveal trypsin inhibitor and urease activity, the levels of glycinin, beta-conglycinin and lectins dropped by 95.5–95.9 %, oligosaccharides by 92.9–93.5 %, phytin phosphorus by 24.4–29.3 % in comparison with raw waste substrate. In conclusion, bacterium Paenibacillus sp. strain ST-4 turns out to be extremely suitable for the transformation of hardly digestible polymers and inaccessible substances of plant origin. The results of performed and planned investigations dealing with molecular-genetic identification of bacterial strain and optimization of soybean fermentation conditions will lay the basis for elaboration of eco-friendly technology for manufacturing high-quality protein fodder product (richprotein fodder product) from seed-processing wastes of soybean and other oleaginous cultures.