Optimization of economic medium and fermentation process of a lepidopteran active native Bacillus thuringiensis strain to enhance spore/crystal production
2015
Salehi Jozani, Gholam Reza | Morad Ali, Mohmmad fati | Abbas Alizadeh, Saeid
The objective of the present study was to design and optimize an economic fermentation process for mass production of a previously isolated native lepidopteran active Bacillus thuringiensis strain (YD5). Firstly, optimum pH and temperature of the strain were studied at Erlenmeyer flask level (incubator). The results showed that the optimum pH and temperature were 7 and 30° C, respectively. To optimize economic medium culture for mass production of the strain, different kinds of available agricultural and food industry wastes were used. This included molasses (sucrose), milk permeate (lactose) and starch liquor (polysaccharide) as carbon source, corn steep liquor as nitrogen source, and sea minerals as mineral sources. The experiments at Erlenmeyer flask level showed that the maximum growth and spore/crystal production by the strain was observed when medium containing 3% hydrolyzed starch, 3% corn steep liquor and 0.003 % sea minerals were used. In the next experiments the optimized economic medium and growth conditions of the strain were evaluated in a batch bioreactor. Also, the effects of primary inoculation concentration, aeration and pH on growth rate, and spore/crystal production were evaluated. The results showed that the maximum growth and spore/crystal production was achieved when 2% preculture concentration and 90% oxygen saturation were used. As result of the designed bioprocess in the present study, the spore/crystal and δ-toxin production were achieved to 5.5 × 109 CFU/ml and 740 mg/l, respectively.
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