Penelitian tentang metode freezing (-4° C) dengan menggunakan freezer lemari pendingin untuk preservasi 13 strain Nostoc [Vaucher 1803] Bornet et Flahault 1886 telah dilakukan. Penelitian bertujuan untuk mengetahui kemampuan tumbuh dan respon tumbuh strain Nostoc setelah dipreservasi. Strain Nostoc yang diujikan berumur 15 hari dalam medium BG11 bebas unsur nitrogen (pH 7,2). Preservasi koloni Nostoc menggunakan DMSO 5% selama 1 dan 7 hari. Koloni Nostoc tanpa penambahan DMSO 5% digunakan sebagai kontrol. Masing-masing perlakuan dan kontrol dilakukan dalam dua kali ulangan.Hasil penelitian menunjukkan sebanyak 11 dari 13 strain (84,62%) dapat bertahan dan berhasil tumbuh setelah preservasi. Sebelas strain Nostoc tersebut menunjukkan respon tumbuh yang berbeda-beda. Metode freezing (-4° C) menggunakan freezer lemari pendingin dapat digunakan sebagai metode preservasi strain Nostoc yang sederhana dan mudah.

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The use of freezing method (-4° C) by using freezer refrigerator for preservation thirteen Nostoc [Vaucher 1803] Bornet et Flahault 1886 strains had been studied. The purpose of this study was to assess strains ability to grow and grow response after being preserved. Nostoc strains cultured in BG11 N free agar (pH 7,2) for 15 days were used. The preservation used 5% DMSO for 1 and 7 days. Nostoc colonies without presence of 5% DMSO were used as a control. Each test was carried out in duplicate.

The results showed that 11 of 13 strains (84,62%) were able to survive and grow after treatment. 11 Nostoc strains showed different grow response. Freezing method (-4° C) by using freezer refrigerator can be used as a simple and inexpensive preservation method for Nostoc strains.