Enhancement of Cellulolytic Nitrogen Fixing Activity of Alcaligenes sp. by MNNG Mutagenesis

For effective degradation of agricultural residues into more useful forms, cellulolytic nitrogen fixing bacteria were isolated from soil samples of central region of Myanmar. Among 32 isolated strains, six best isolates (three strains of Azomonas agilis, two strains of Azotobacter chroococcum, and one strain of Alcaligenes sp.) were selected. Best strains were selected by their nitrogen fixing activities. Nitrogen fixing bacteria cannot excrete significant amount of ammonia into their environment. To improve cellulolytic nitrogen fixing activities, Alcaligenes sp. among six isolates was muatgenized with chemical mutagen, MNNG. From treatment of Alcaligenes sp. with three concentrations of MNNG (7.5 ppm, 10 ppm and 12.5 ppm), six potential mutant colonies were obtained. After screening of nitrogen fixing activities of wild type and mutagenized strains, four out of six mutant strains excreted higher amount of ammonium concentration than wild type strain. Although wild type strain of Alcaligenes sp. excreted 46.64 ppm of ammonium concentration, 101.35 ppm of ammonium concentration was excreted by mutant strain (M2-F) of Alcaligenes sp. According to results obtained, 10 ppm of MNNG was more effective for obtaining better mutant strain for nitrogen fixing activity. Although nitrogen fixing activities of mutant strains were increased, cellulolytic activities were decreased than those of wild type strain. Reducing sugar concentrations produced by all mutant strains were decreased using cellulose and CMC as substrates than wild type strain.