Failure of colony growth in probiotic Lactobacillus casei Shirota as result of preservative sorbic acid

(1) Steele Canyon Charter High School, Spring Valley, California
Cover photo for Failure of colony growth in probiotic <i>Lactobacillus casei</i> Shirota as result of preservative sorbic acid

Preservatives have been a part of the food industry for years. Even before the days of bacterial pesticides and other antimicrobial technology, people used items like salt to prevent bacteria from growing. However, questionable claims on the negative effects of preservatives have been made, starting a new wave of “clean eating.” In this study, we tested the proficiency of different concentrations of the antimicrobial sorbic acid to inhibit the probiotic Lactobacillus casei Shirota. We hypothesized that sorbic acid’s use as a bacterial deterrent would also target this bacterial strain of Lactobacillus. We inoculated petri dishes in trials of 0%, 0.03%, and 0.1% sorbic acid concentrations and examined them over the 36-hour study. The results supported our hypothesis, with the colony count of L. casei Shirota having significant decreases at all concentrations of sorbic acid. These results additionally suggest that even under the FDA sorbic acid restrictions of 0.03% concentration, damaging effects could be seen in L. casei Shirota.

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