Bacillus Stearothermophilus Sporulation Response to Different Composition Media

Abstract

To evaluate the effectiveness of 11 commonly used ingredients to improve Bacillus stearothermophilus ATCC 7953 sporulation, with high spore yields in a short period of incubation, 32 composition media were set up by a fractional factorial 2_IV^11–6 design at two levels: D-glucose (0.018–0.25%), L-glutamic acid (0.040–0.10%), yeast extract (0.050–0.40%), peptone (0.30–0.50%), sodium chloride (0.001–1.0%), magnesium sulfate (0.001–0.20%), ammonium phosphate (0.010–0.035%), potassium phosphate monobasic (0.050–0.25%), calcium chloride (0.001–0.05%), ferrous sulfate (0.0003–0.002%), manganese sulfate (0.001–0.50%). The largest variation on Log₁₀ CFU response took place due to sodium chloride main effect, by changing it from low to high levels. Magnesium sulfate, calcium chloride, and ferrous sulfate were split and exerted no detectable main effect influence on sporulation. Setting up two 16 runs for sodium chloride effect, in each of which the remainder levels were kept constant, other components contribution was studied. At low sodium chloride, best average 7.25 Log₁₀ CFU yielded by fastening yeast extract and peptone at high level, and remainders at low level. Considering high level of sodium chloride, peptone, yeast extract and ammonium phosphate kept at high level and remainders at low level confirmed the best sporulation yield. Adjusted models evidenced a strong influence of joint yeast/peptone effect, associated to ammonium phosphate contributing positively. The reduced incubation period from 15 days to 3–6 days at 62°C was attained for all 32 experimental runs.