The correlation of carbon source and ammonium accumulation in culture broth by nitrogen-fixing bacterial isolates

Several nitrogen-fixing bacteria were isolated from the agricultural soil samples of Kyaukse District, Mandalay Division, Myanmar. Among the isolated strains K-3 and T-7 were identified as Azotobacter beijerinckii and Azotobacter vinellandii and and M4 was identified as Stenotrophomonas maltophilia.. Although other studies have reported that wild types of the nitrogen-fixing bacteria cannot produce excess ammonia, our experiments indicated that these three strains accumulate relatively high amounts of ammonia in medium with a low concentration of sugar. Azotobacter beijerinckii accumulated approximately 0.48 mM of ammonia after incubation for 96 hour in 0.5% nitrogen free glucose mineral medium (NFGMM), while A. vinelandii accumulated approximately 0.36 mM in 0.25% nitrogen free fructose mineral medium (NFFMM) after 96 hour. Stenotrophomonas maltophilia accumulated highest amounts of ammonia in glucose supplemented medium approximately 0.52mM after 96h incubation. A. beijerinckii also accumulated ammonia in fructose, galactose, and sucrose media. Azotobacter vinelandii accumulated ammonia mainly in fructose and Stenotrophomonas maltophilia accumulated ammonia in glucose, sucrose an