Two actively marked toxic strains of Bacillus sphaericus NSE1 and NSE2,  previously isolated from the soil of North Sinai in Egypt, identified morphologically, biochemically and assayed biologically against mosquito larvae, were used in the present study along with the reference strains of Bacillus sphaericus 1593 and 2297. The PCR product profiles indicated the presence of genes encoding Bin A, Bin B and Mtx1 in all analyzed strains; they are consistent with protein profiles. PM achieved the highest significant yield during the first 72 hr of fermentation course, but after 120 hr NYSM attained the highest significant yield of 1.1 - 1.3 × 10⁹ CFU/ml and stand with PM without significant differences. AYEM, LBM and GGSEM, in that order, came after. The maximum yield of spores was reached at the end of the fermentation time in both PM and NYSM followed by GGSEM. However, the highest significant sporulation rate (88.5 - 100%) was obtained in NYSM followed by PM and GGSEM (71.4 – 93.3%), (40.0 – 80%), respectively. The synthesis of protein was observed only from 6 hr (NSE1, 2297), 9 hr (1593) and 12 hr (NSE2) onwards and reached the maximum level after 120 hr. The significant highest quantities was attained in PM. Local strains, NSE1 and NSE2, respectively, always produced significantly higher protein amounts in fermentation media than the standard strains 2297and 1593. The maximum toxicity against 3^rd instar of Culex pipiens (LC₅₀ 5 x 10³ and 8 x 10³ CFU/ml) was noticed with local strains NSE1 and NSE2, respectively in PM by 5 days without significant differences. In all of the fermentation runs, changes in pH showed a similar pattern, rising to reach about 8.3 - 9.0 at the end of fermentation.