N2 fixation and methane oxidation activity of mixed of culture of Azotobacter sp., Azospirillum sp., and Methanotrophic Bacteria

Abstract

Metanotrophs bacteria are methane oxidizing bacteria. Methanotrophic bacteria especially type II and type X were also able to fix nitrogen using nitrogenase enzyme. This reasearch was conducted to determine activity of methane oxidation and nitrogen fixation of four isolates of methanotropic bacteria i.e. BGM 1, BGM 5, BGM 9, and SKM 14 which were combined with nitrogen-fixing bacteria (Azotobacter sp. and Azospirillum sp.). Six combinations were cultured and then inoculated into nitrogen free NMS medium. Activity of methane oxidation and nitrogen fixation activity was analysed. The highest methane oxidation activity was found in the mixed culture of BGM 9, BGM 5, Azotobacter sp., and Azospirillum sp. isolates. The activity was 184.5 x 10-8 ìM/cell /day. The highest accumulation of ammonium was found in the mixed culture of BGM 5, BGM 9, and Azotobacter sp. isolates. The concentration of accumulated ammonium was 4.075 ìM. Methane oxidation activity and ammonium accumulation of methanotrophic bacteria showed higher result when they were combined with nitrogen fixing bacteria.

Bakteri metanotrof merupakan bakteri pengoksidasi metan. Selain itu, bakteri metanotrof tipe II dan tipe X juga mampu memfiksasi nitrogen karena adanya enzim nitrogenase. Tetapi aktivitas oksidasi metan dihambat oleh keberadaan amonium. Penelitian ini dilakukan untuk menguji aktivitas oksidasi metan dan fiksasi nitrogen keempat isolat bakteri metanotrof yaitu BGM 1, BGM 5, BGM 9, dan SKM 14 yang dikombinasikan dengan bakteri penambat nitrogen (Azotobacter dan Azospirillum). Sebanyak 6 kombinasi dikulturkan kemudian diinokulasikan ke campuran media NMS tanpa unsur N, kemudian diuji aktivitas oksidasi metan dan fiksasi nitrogen. Aktivitas oksidasi metan tertinggi terdapat pada kombinasi isolat BGM 5, BGM 9, Azospirillum, dan Azotobacter yaitu sebesar 184,5 x 10-8 ìM/sel/hari . Aktivitas akumulasi amonium tertinggi terdapat pada kombinasi isolat BGM 5, BGM 9, dan Azotobacter yaitu sebesar 4,075ìM. Aktivitas oksidasi metan dan akumulasi amonium bakteri metanotrof menunjukkan hasil yang lebih tinggi saat dikombinasikan dengan bakteri penambat nitrogen.