Effect of C/N ratio of culture medium on biomass production and sporulation of some Bacillus thuringiensis isolates from Sudanese soils

Abdulwahab A. Ahmed, Hamid A. Dirar


A physiological study was conducted on some parameters affecting growth and sporulation of B. thuringiensis isolates derived from Sudanese soils. The effect of carbohydrate and nitrogen concentrations in the growth medium was investigated on three B. thuringiensis strains, EA3, N10 and BR12. It was found that all strains produced high weight of dry biomass when the concentration of carbon was kept at a level of 0.4% (w/v) with various concentrations of nitrogen. The effect of C/N ratio on the process of sporulation was found to be variable among selected strains. At lower sugar concentrations, strain EA3 tended to have a lower sporulation rate with an increase in Nlevel. However, relatively higher carbon levels were detrimental to strain BR12 with an increase in N concentration. On the other hand, the highest sporulation rate with strain N10 was obtained at 4:1(C/N) and the lowest at 1:1(C/N). The effect on cell growth in terms of spore count for all ratios was found to be highly significant at the 1% level (P<0.01).

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