Effects of varied culture conditions on crude bacitracin produced by Bacillus subtilis isolated from the soil

Aim: To determine the effects subjecting Bacillus subtilis to different cultural conditions will have on the crude Bacitracin produced in inhibiting the growth of known susceptible organisms.

Method: Bacillus subtilis known to be a bacitracin producer was isolated from the soil and identified. The isolate was used to produce bacitracin under various culture conditions with peptone water serving as a basal fermentation medium. The resultant crude bacitracin produced was checked for its antimicrobial activity against Staphylococcus aureus by using the agar well diffusion method. Culture conditions varied were the addition of glycerol, arabinose, fructose, mannose, sucrose, urea, MgSO4, CaCO3, KCl, sodium citrate, and the adjustment of initial pH at pH 5, 6, 8 and 9. Bacitracin production was done at 37 oC for 4 days in an orbital shaker incubator rotating at 150rpm.

Result: The antimicrobial activity against the test organism (Staphylococcus aureus) was determined by the mm of the zone of inhibition, with the best result obtained from the addition of glycerol (14 mm) and the least zone of inhibition was observed from the addition of MgSO4 (3 mm). Also, pH 8 produced the best result (20 mm), while at pH 5, the antimicrobial activity of the crude bacitracin was reduced (14 mm).

Conclusion: Bacitracin produced from Bacillus subtilis under various culture conditions has antimicrobial effect against Staphylococcus aureus. The highest antimicrobial activities can be gotten by the addition of glycerol and by raising the initial pH of the basal broth to pH 8 while that produced by addition of MgSO4 will have the lowest antimicrobial effect.