BIOINOCULANTS OF AZOTOBACTER VINELANDII NBIMCC 1619 - PHYSIOLOGICAL, KINETIC, AND TECHNOLOGICAL CHARACTERISTICS

Considerable attention is now being paid to environmentally friendly agricultural practices that reduce reliance on chemical inputs while maintaining high crop productivity and preserving soil health. Among the most promising sustainable approaches is the use of plant growth-promoting rhizobacteria (PGPR), which are essential components of sustainable agriculture and integrated nutrition management practices. Among them, bacteria of the genus Azotobacter have attracted scientific and commercial interest because they combine efficient atmospheric N2 fixation with numerous plant growth-promoting (PGP) properties.The present study focuses on Azotobacter vinelandii NBIMCC 1619 PGP characteristics and the formulation of a bioinoculant preparation. A systematic fermentation and processing strategy was developed under controlled conditions to address the key challenges of producing effective N2-fixing PGPR bioinoculants. The biochemical profile of the strain revealed simultaneous expression of N2 fixation, phytohormone biosynthesis, siderophore production, phosphate solubilization, and extracellular enzyme production. An optimization process resulted in the development of a nutritionally balanced, agriculturally relevant N-free medium and a cultivation regime with DO2 of 30 %, a temperature of 29°C, and a pH of 7.1. A fed-batch strategy of continuous substrate feeding over a 12 h period was implemented to result in high biomass production and N2-fixing performance of the bioinoculant. Its stability at 4°C and in freeze-dried form with cryoprotection was proved. Thus, the physiological, kinetic, and technological characteristics of A. vinelandii NBIMCC 1619 demonstrate its potential for large-scale production under economically satisfactory conditions as a bioinoculant to increase crop productivity.