EVALUATION AND IMPROVEMENT OF AN ANTIMICROBIAL PRODUCT FROM Bacillus cereus MLAMC 271 Authors: Alshehri A.N.Z.
ABSTRACT
Foodborne pathogens pose risks in food products, hence the need to seek alternative
antimicrobials for reducing these pathogens. The aim of this work was to define the
antimicrobial features of the substances from Bacillus cereus MLAMC 271 against Gram
negative (Salmonella Enteritidis MLAMC 804, Pseudomonas aeruginosa MLAMC 538, and
Escherichia coli MLAMC 925) and Gram positive (Bacillus subtilis, MLAMC 853,
Staphylococcus aureus, MLAMC 638 and Listeria monocytogenes MLAMC 163) pathogens.
Bacterium Salmonella Enteritidis MLAMC 804 has been utilized as test organism to
determine effect of several operation conditions such as time, pH (4.5 – 11.5), temperature
(25–45ºC), whey powder (10–20 g/L) or glucose concentration (0–20 g/L) on the rate of the
secretion of antimicrobials. The results showed antimicrobial substances of B. cereus
MLAMC 271to be efficient against all pathogens tested except for P. aeruginosa MLAMC
538. Antimicrobial levels peaked at 20-27 h of bacterial growth, optimal pH was 8.5, and
optimal temperature 35°C. Production of antimicrobial was highest when only nitrogen
sources were present and glucose was absent. Antimicrobials were produced in the media that
contained only whey powder, which suggests the potential of whey powder as a medium for
satisfactory production of efficient antimicrobials using B. cereus MLAMC 271 against wide
spectrum of the bacteria.
Keywords: Bacillus cereus, Antimicrobial activity, Whey powder, Pathogens, Gram
negative, Gram positive
