Free living nitrogen fixing bacteria are those that lives freely on rhizosphere of a young growing plant or those living in a close association with root of plants (Rhizobacteria) but not symbiotically. In most tropical soil, Nitrogen and other essential nutrients element are the most limiting nutrients which deficiencies could lead to slow growth and reduced crop production. Free living nitrogen fixing bacteria has the potential of secreting nitrogenase enzymes and produces organic acids such as glycolic, acetic, malic, succunic acids which fix atmospheric nitrogen directly into the soil for plants growth and development. To this end, the study on isolation, identification and screening of Azotobacter chroococcum from soil of Keffi, Nasarawa State, Nigeria was carried out from May to September 2018. Soil samples were collected from eight different locations and Azotobacter strains were isolated and identified using standard microbiological methods. The 16SrRNA gene sequence analysis of the strain showed maximum similarity of 96% with Azotobacter chroococcum of the reference type strain deposited in RDP Gen Bank database. Azotobacter strains isolated from four different locations showed coloured zone ranging between 16-10mm. Similarly, Percentage amount of nitrogen released by each Azotobacter strain in the culture broth ranging between 1.19% -5.11% in an increasing order.

Commercial crop production and many other agro-industrial activities generate large amount of cellulose, hemicelluloses and lignin. This research is aimed at the utilization of some of these agro-wastes for the cultivation of Pleurotus ostreatus (Oyster Mushroom) in Keffi area. The agro-wastes (cassava peels (CP), banana leaves (BL), saw dust (SD), yam peels (YP) and groundnut shells (GS) were collected, sorted, shredded, sterilized and inoculated with equal proportions of Pleurotus ostreatus (P. osreatus) for a period of four weeks. Rate of mycelia growth, temperature, mycological identification, nutritional contents of P. osreatus harvested and microbial isolation from the spent mushroom substrates were analyzed. The numbers of days for complete ramification of the substrates by mycelia of P. osreatus were; 18 days for BL and GS, 24 days for CP and YP while 30 days for SD. The room temperature within the period of exposure for fruiting of the ramified substrates ranges between 22°C to 28°C in the morning, 23°C to 30°C in the afternoon and 25°C to 31°C in the evening throughout the period of exposure. The nutritional contents of the Pleurotus ostreatus from the different substrates analysed were, Moisture content was highest in SD (87.05%) and lest in GS (80.71%), Protein content was highest in GS (38.13%) and lowest in BL (16.43%), Lipid content was highest in GS (4.62%) and lest in CP (1.83%), Carbohydrate content was highest in CP (78.40%) and lest in GS (71.66%), Fibre content was highest in BL (9.10%) and lest in YP (8.20%) while Ash content was highest in GS (7.37%) and lest in YP (6.42%). Five bacteria species (Bacillus cereus, Pseudomonas aeruginosa, Micrococcus roseus, Escherichia coli and Bacillus subtilis) and two yeast species (Candida albicans and Candida tropicalis) were isolated from the spent mushroom substrates.