Isolation and Growth of N2-Fixing Cyanobacteria from Organic Agricultural Areas in Sanamchaikate, Chachoeng-Sao Province, Thailand

Forty-five isolates of nitrogen-fixing cyanobacteria were obtained from organic soils at Chachoeng-Sao province. Of these, the most diverse genus belonged to Nostoc (31 isolates), followed by Tolypothrix (8 isolates), Anabaena (1 isolate), Calothrix (1 isolate), Fischerella (1 isolate), Scytonema (1 isolate) and 2 isolates were unknown. Five predominant isolates, including Nostoc sp. TUBT03, Nostoc sp. TUBT04, Nostoc sp. TUBT05, Nostoc sp. TUBT06 and Tolypothrix sp. TUBT31, were selected to study for growth in BG-11 liquid medium without nitrogen source (BG-110) at 25°C on a 120 rpm rotary shaker and 12: 12 light-dark cycles. Samples were taken every 5 days for 45 days and packed cell volume (PCV) and dry cell weight (DCW) were examined. Accoding to DCW, Nostoc sp. TUBT05 had the highest specific growth rate of 0.2952 d-1, follow by Nostoc sp. TUBT04 (0.2424 d-1), Nostoc sp. TUBT06 (0.2184 d-1), Nostoc sp. TUBT03 (0.1968 d-1) and Tolypothrix sp. TUBT031 (0.0528 d-1), respectively. The highest PCV of 105.79 ml L-1 was shown by Nostoc sp. TUBT06, followed by Nostoc sp. TUBT03 (75.72 ml L-1), Nostoc sp. TUBT05 (61.56 ml L-1), Nostoc sp. TUBT04 (28.22 ml L-1) and Tolypothrix sp. TUBT031 (21.69 ml L-1), respectively. Tolypothrix sp. TUBT031 showed the highest DCW (2.02 g L-1), follow by Nostoc sp. TUBT03 (1.02 g L-1), Nostoc sp. TUBT06 (0.93g L-1), Nostoc sp. TUBT04 (0.74 g L-1) and Nostoc sp. TUBT05 (0.60g L-1), respectively. All these 5 cyanobacterial isolates can grow well in BG-110. Therefore, they can be applied as biofertilizers. Further study on cyanobacterial biochemical substance production is needed.