The aim of the study was to evaluate the biotechnological potential of thermophilic mi-croorganisms isolated from chernozem soil during composting of poultry manure. The ef-ficiency of the strains was determined by their effect on organic matter degradation, humi-fication intensity, and nitrogen accumulation. The correlation between the quality indica-tors of composting process was assessed with the gross values, taking into account the proportion of compost fractions. The strains were identified as: Aeribacillus pallidus KCTC 3564T (cellulolytic), Neobacillus sedimentimangrovi FJAT-2464T, Aeribacillus composti N.8T, Caldifermentibacillus hisashii N-11T (nitrogen fixers) and Acinetobacter pittii CIP 70.29T, Pseudomonas plecoglossicida NBRC 103162T (nitrifies). It was found that all the bacteria increase the proportion of small fractions by 19.0-19.9%. The gross content of humic acids increases under the influence of nitrifiers (15.5%) and nitrogen fixers (5.5%). The total nitrogen content increases under cellulolytics (13.8%) and nitrogen fixers (20.2%). The smallest fraction (≤0.25 mm) in nitrogen fixers and nitrifies variants has the greatest bioreclamation properties, by 16.4% and 12.9%. Targeted microbial strains pro-vide the direction of the transformation processes while biocomposting. It can also be con-cluded that assessing the quality of composting based on the fraction distribution can be a promising element of the biofermentation process monitoring.