Tuesday, September 27, 2011

THE GROWTH OF Azotobacter chroococcum Beijerinck IN COCONUT WATER (Cocos nucifera Linneus)

Mochamad Alqi Harlianto1 and I Nyoman P. Aryantha1,2


1Microbiology-Genetics-Cell Molecular Biology Division School of Life Sciences and Technology
2Center for Life Sciences

Institut Teknologi Bandung
Jalan Ganesha 10, Bandung 40132
Email : nyoman@sith.itb.ac.id

ABSTRACT

Nitrogen is the most important fertilizer for plant growth, and it is required in large quantity as the main component of protein, nucleic acid, and other cell components. Plant can only absorb nitrogen in form of ammonium and nitrate. Azotobacter chroococcum can provide ammonium for plant by nitrogen fixation from atmosphere by non-symbiotic interaction (free living). In order to develop biofertilizer (nitrogen fixing agent), this research was aimed to find out the maximum growth of Azotobacter chroococcum in coconut water based medium. The focuse of research was to determine the concentration of coconut water and inoculum to produce maximum Azotobacter chroococcum cell biomass. The experiment was conducted by substrate optimization with various coconut water concentration i.e: 25%, 50%, 75%, and 100% (v/v). Six inoculum concentration were evaluated i.e: 2,5%, 5,0%, 7,5%, 10,0%, 12,5%, and 15,0% (v/v). Cell biomass was measured with Optical Density method using spectrophotometer, pH with pH meter, and reducing sugar by using Somogyi-Nelson method. Cell number was obtained by converting OD value into cell number by using a standard curve. The result indicates that coconut water concentration of 25%v/v was the best with a growth rate maximum of 1,45 cell/hour. The best inoculum concentration was 2,5% (v/v) with maximum growth rate of 0,85 cell/hour. This result approves that coconut water can be used as growth medium for Azotobacter chroococcum production to develop biofertilizer.
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Keyword : Azotobacter chroococcum , coconut water, non-symbiotic bacteria, nitrogen fixation.

Sunday, September 25, 2011

NODULASI SILANG ANTARA BAKTERI NODUL TANAMAN LEGUMINOSAE BERBEDA SPESIES PADA TANAMAN KEDELAI HITAM [Glycine soja (Moench) F.J. Herm)]

I NyomanPugeg Aryantha, Tri Yuliana, Devi Ismidianti Bakteri penambat nitrogen simbiotik selama ini dikenal bersifat spesifik terhadap tanaman inang tertentu. Penelitian ini mencoba mempelajari kompatibalitas bakteri nodul dari beberapa spesies tanaman Leguminosae berbeda dan pengaruhnya pada tanaman kedelai hitam (Glycine soja). Penelitian ini meliputi (1) Isolasi bakteri nodul dari berbagai tanaman Leguminosae (2) uji kompatibilitas bakteri hasil isolasi terhadap tanaman uji (3) Identifikasi bakteri hasil seleksi (4) Pemilihan dosis jumlah inokulum (106 dan 109 cfu/ml) (5) Pembandingan perlakuan dengan penambahan pupuk NPK (NPK 50%). Hasil isolasi adalah berupa 11 isolat dan hanya 5 isolat yang kompatibel membentuk nodul yang teridentifikasi sebagai Rhizobium sp.1 (sumber:Mimosa pudica), Rhizobium sp.2 (sumber:Centrosema pubescent), Bradyhizobium japonicum (sumber:Glycine max), Rhizobium phaseoli (sumber:Phaseolus vulgaris) dan Sinorhizobium fredii (sumber:Vigna unguiculata). Inokulasi dengan isolat Rhizobium sp. 1 dan Rhizobium sp. 2 dengan dosis 109 cfu/ml dan 106 cfu/ml merupakan isolat yang paling efektif dengan pengaruh nyata terhadap pertumbuhan vegetatif tanaman kedelai hitam. Perlakuan inokulasi dengan kedua isolat bakteri secara tunggal dan campuran + NPK 50% dapat meningkatkan berat kering biomassa tanaman uji secara nyata dibandingkan dengan kontrol negatif dan kontrol positif. Peningkatan berat kering biomassa dihasilkan sebesar 34,4% untuk kombinasi Rhizobium sp.1+NPK 50%, 31,99% untuk Rhizobium sp. 2 + NPK 50% dan 45,76% untuk inokulum campuran Rhizobium sp. 1+Rhizobium sp.2+NPK 50%. Dari penelitian ini dapat disimpulkan, bahwa inokulasi silang antara isolat bakteri nodul dari tanaman inang berbeda spesies adalah bersifat kompatibel dan memberikan efek positif terhadap pertumbuhan vegetatif tanaman kedelai hitam Glycine soja. Kongres Nasional Himpunan Ilmu Tanah Indonesia IX, 5-7 Desember 2007, Yogyakarta


ABSTRAK



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Kata Kunci : Nodulasi silang, Rhizobium sp., Glycine soja, Bakteri nodul, fiksasi Nitrogen, symbiosis mutualistik