Inhibition of Biofilm Formation by Food Waste Extracts and Iron Modulation

Introduction: Biofilms are complex microbial communities, exhibiting antibiotic resistance that makes their inhibition difficult. Iron availability is known to affect biofilm formation. Biofilm inhibition can be achieved by altering iron concentrations. One aspect of this study involved the evaluation of the effects of iron salts such as ferric ammonium citrate (FAC), ferrous sulfate (FeSO4), and chelating agents like ethylenediaminetetraacetic acid (EDTA) on biofilm formation. In addition, the study explored the effect of bioactive compounds from natural sources, including plant extracts and food waste derivatives, for biofilm inhibition and control. Methods: This study investigated the effect of iron salts on biofilm formation in Staphylococcus aureus and Escherichia coli. Additionally, methanolic extracts of food wastes of onion, potato, sweet lime, and banana peels were screened for their antimicrobial and anti-biofilm activity. Biofilm quantification was performed using crystal violet (CV) staining assays. Results: 50 μM of Ferrous sulphate and EDTA was used, which significantly inhibited biofilm formation in both S. aureus ATCC 25923 and E. coli. DH5α FAC increased E. coli DH5α biofilm formation by 27%, while decreasing S. aureus ATCC 25923 biofilms by 48%. In contrast, the addition of Ferrous Sulphate led to a 61.12% reduction in E. coli DH5α biofilm. EDTA, an iron chelator, significantly reduced biofilm formation in both S. aureus ATCC 25923 and E. coli DH5α by 64% and 63%, respectively. Food waste extracts exhibited varying degrees of biofilm inhibition: hot onion extract showed a 63% reduction in E. coli DH5α biofilm, while its cold counterpart reduced E. coli DH5α and S. aureus ATCC 25923 biofilms by 36% and 27%, respectively. Cold banana extracts inhibited E. coli DH5α biofilm by 72%, and potato extracts (hot and cold) reduced E. coli DH5α biofilm by 76.30% and 77.70%, and S. aureus ATCC 25923 by 59% and 32.04%, respectively. Sweet lime hot extract reduced S. aureus ATCC 25923 biofilms by 42.30%, whereas its cold extract led to enhanced biofilm formation. Discussion: The findings demonstrate that both iron modulation and natural bioactive compounds derived from food wastes affect the dynamics of biofilms differently in Gram-positive and Gram-negative bacteria. Iron limitation and chelation effectively disrupted biofilm establishment, while metabolites from food wastes exerted additional inhibitory effects, highlighting an eco-friendly approach to biofilm control. The variations in the effects of different extracts suggest that the stability of bioactive compounds and temperature play crucial roles in biofilm inhibition. Conclusion: In this study, it was observed that iron modulation and the use of bioactive compounds derived from food waste can effectively inhibit biofilm formation. These findings suggest sustainable strategies for biofilm control and could aid in developing alternative antimicrobial approaches.