2017 ASHS Annual Conference

This study was performed to optimize the growth and activity of Bacillus thuringinesis KKY which had been isolated from (soil). The KKY strongly inhibited all tested pathogenic fungi in generally used laboratory grade medium, LCP(LB 0.67%, Colloidal chitin 6.67%, Yeast extract 0.03%, PDB 0.8%, Agar 2%). In order to reduce the cost of the medium, the cost-effective medium based on fertilizer, power chitin and crab shell powder was developed which is called Black-White (BW). In this medium, different concentrations of NaCl, yeast extract (YE) and tryptic soy broth (TSB) was added. The highest growth of KKY colonies was observed in the BW agar medium containing 0.5% NaCl, 0.05% YE and 0.01% TSB respectively. When both KKY and pathogenic fungi were grown on BW agar medium, KKY strongly inhibited all tested pathogenic fungi the same as that on LCP. The growth rate and enzyme activities of KKY, and chemical change of culture broth were investigated in the BW with 0.05% TSB medium at 30ºC, 40ºC and 50ºC for 7 days. The maximum growth rate was discovered at 30ºC on day 2 incubation period with 1.3x10⁸ CFU/ml. The highest growth value was 1.62x10⁶ CFU/ml at 40ºC on day 7, which was 80 times reduced compared to 30ºC. However, no growth was detected at 50ºC during incubation period. The maximum protease activity at both 30ºC(8.72unit/mL) and 40ºC(6.46uni/mL) incubation was found on day 7, but for β-1,3 glucanase, the highest value was examined on day 5 for 30ºC(0.78unit/mL) and on day 2 for 40ºC(0.83unit/mL). Also, chitinase activity was the greatest at 40ºC(1.54unit/mL) on day 2, while on day 7 at 30ºC incubation(1.54unit/mL). The pH value of the culture broth (7.4) was slightly decreased day by day and finally reached 6.49 at both 30ºC and 40ºC. The EC value of the culture remained constantly around 3mS/m during the entire incubation time. Based on these results, the culture of B. thuringiensis KKY in the cost-effective medium (BW medium) at 30ºC for 2 days could be considered for agricultural use.