Potential of Medicinal Plants and Bacteriocins Against Foodborne Pathogens

Bio-preservation is the use of natural antimicrobial compounds from medicinal plants, herbs and spices and bacteriocins produced by lactic acid bacteria (LAB). The plants and spices produce various metabolites having antimicrobial activities against food spoilage and pathogenic micro-organisms. Some microorganisms including bacteria and fungi also produce several metabolites with antimicrobial potentials. The present study was aimed to characterize the extracts from selected plants and spices and bacteriocins from LAB as food preservatives through in-vitro activities, chemical profiling and food applications. The medicinal plants/spices (tejpal, green tea, thyme, cinnamon, nutmeg and black pepper) and LAB (Streptococcus thermophiles, Lactobacillus acidophilus, Lactococcus lactis ssp. lactis and Lactococcus lactis ssp. cremoris) were selected. Plants and spices were extracted and tested for antimicrobial, thrombolytic and antioxidant activities, biofilm and DNA damage inhibition, hemolytic and Ames assays. The ethanolic extracts of green tea and thyme were selected on basis of optimal levels of activities and characterized through spectroscopy for chemical profiling. The LAB were propagated and tested for their antimicrobial activity. The green tea and thyme extracts and bacteriocin producing LAB were added individually and in combinations in cheese and bread manufacturing to evaluate their role as food preservatives. The antibacterial potential of extracts showed the significant extent of the activity against B. subtilis and E. coli. The antifungal activity exhibited the highest antifungal activity by C. sinensis against A. niger and A. flavus. Antioxidant potential exhibited the highest phenolic and flavonoid content in C. sinensis and C. verum. The radical scavenging DPPH assay also showed the significant antioxidant capacity of selected plants. The cytotoxic evaluation through hemolytic assay and DNA damage protection showed no toxicity in any plant extract. The characterization through chromatography and spectroscopy confirmed the presence of phenolics, flavonoids and alakloids. The antibacterial assay performed to assess bacteriocins activity of selected LAB revealed their strong bacteriocins activity. The food application concluded that bacteriocins producing LAB alone or in combination with selected plant extracts can efficiently be added in cheese and bread as preservatives. It was concluded that the green tea and thyme as well as bacteriocins producing LAB has potential to act as food preservatives. They can provide remarkable preservation prospects, if added in combinations.