Evaluating the Impact of Soft Drinks on Bacterial Growth and Biofilm Development

Sarah Rafie

Co-Presenters: Individual Presentation

College: Hennings College of Science Mathematics and Technology

Major: BS.BIO/CELL/MOLEC

Faculty Research Mentor: Bendaoud, Meriem  

Abstract:

Soft drinks are consumed globally in both regular and diet forms, and many are marketed with added vitamins or plant extracts. While their metabolic and health impacts are well studied, little is known about their antimicrobial properties and potential influence on microbial growth. This study investigates the antimicrobial activity of Monster, Red Bull, and Ginger Ale, along with their diet counterparts and vitamins B2 and B3, at varying concentrations. A broth assay using 96-well plates was performed against 20 microorganisms, including both Gram-negative and Gram-positive bacteria and fungi. Growth inhibition and biofilm formation were assessed. Monster and Diet Monster showed strong inhibitory effects against several bacterial strains, including Pseudomonas aeruginosa, Bacillus cereus, Escherichia coli, and Staphylococcus aureus. Ginger Ale and Diet Ginger Ale produced variable results, sometimes increasing and other times reducing microbial growth. Red Bull and Diet Red Bull displayed moderate inhibition, primarily against Gram-positive species such as Staphylococcus epidermidis, Streptococcus oralis, and S. aureus. At higher concentrations, several beverages promoted biofilm formation. Vitamins B2 and B3 showed no significant activity, except for slight inhibition with vitamin B3 against P. aeruginosa. These findings indicate that certain energy drinks, particularly Monster and Diet Monster, contain compounds with notable antimicrobial properties. The observed biofilm formation at higher concentrations raises concerns about unexpected microbial responses. Future work will focus on isolating and characterizing the active compounds responsible for these effects to better understand their biological significance.