Kesan penambahan ammonium sulfat, (NH4)2SO, (sebagai sumber nitrogen bukan organik tunggal) terhadap pensporaan Bacillus thuringiensis subsp. aizawai strain SN2 dalam kultur kelompok telah dikaji. Peratus spora tertinggi (76 %) dikesan selepas 96 j pengkulturan dalam medium yang mengandungi 1.5 gL-1 (NH4)2SO4. Peratus spora tertinggi sebanyak 82 % juga dikesan dalam sampel 96 j apabila medium yang mengandungi 1.5 gL-1 (NH4)2SO4 ditambah dengan 3.0 gL-1 (NH4)2SO4 pada jam keenam selepas mula fermentasi. Peningkatan peratus spora didapati tidak berkaitan dengan jumlah kandungan nitrogen tetapi berkaitan dengan masa penambahan sumber nitrogen.
Kata kunci: Bacillus thuringiensis subsp. aizawai strain SN2, masa penambahan nutrien, kultur kelompok
The effect of ammonium sulphate (as the sole inorganic nitrogen source) on the sporulation of Bacillus thuringiensis subsp. aizawai strain SN2 was investigated in batch fermentation. The spore percentage of 76 % was achieved at 96 h after inoculation into a medium containing initial cencentration of 1.5 gL-1 ammonium sulphate. In another experiment, the maximum spore percentage of 82 % was obtained after 96 h inoculation in a medium with initial concentration of 1.5 gL-1 (NH4)2SO4 followed by an addition of 3.0 gL-1 (NH4)2SO4 after 6 h of fermentation. The increase in Bacillus thuringiensis spore percentage was not a function of total nitrogen content in the medium but was a function of the time nitrogen being added.
Key words: Bacillus thuringiensis subsp. aizawai strain SN2, timing addition, batch fermentation
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