Oplimization conditions for growth and production of metabolites inhibiting fungal pathogens of rice from Bacillus spp.
1999
Saichai Kaew-on
Cultivation of B. subtilis NSRS 89-26 and Bacillus sp. MK007 was investigated in various media and conditions. The results showed that the optimum media for both Bacillus spp. were modified Sandril medium with 2.0 percent sucrose, 0.5 percent urea and with 1.0 percent sucrose, 0.1 percent ammonium hydrogenphosphate, respectively. The optimum conditions for growth of B. subtilis NSRS 89-26 and Bacillus sp. MK007 were 30 and 35 deg C at initial pH of 7.0, respectively. The cultivation of B. subtilis NSRS 89-26 in 2 litre fermentor with constant pH at 7.0 gave higher yield (0.219 g/g and production rate (7.39*10*[11 cfu/l h comparing to that without controlling. While Bacillus sp. MK007 well grew in both controlled and without controlled pH conditions. The yield and production rate were 0.235, 0.226 g/g and 1.06*10*[11), 1.40*10*[11) cfu/l controlled and without controlled pH conditions, respectively. B. subtilis NSRS 89-26 could grow in modified Sandril medium with molasses (1.0 percent reducing sugar) and 2.0 percent soybean meal. The yield were 4.72*10*[11) and 4.58*10*[11) cfu/g (at 48 hrs) in B. subtilis NSRS 89-26 and Bacillus sp. MK007, respectively. The results also showed that Bacillus spp. could produce some metabolites that inhibited the growth of Pyricularia oryzae and Rhizoctonia solani (rice pathogens) at more than 80 and 70 percent, respectively.
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