Investigation of the antimicrobial activity of polyphenol-enriched extracts against probiotic lactic acid bacteria

Abstract

The antimicrobial activity of polyphenol-enriched extracts from industrial plant by-products (strawberry and bilberry press residues and distilled rose petals) against probiotic lactic acid bacteria (Lactobacillus delbrueckii subsp. bulgaricus S10 and S19; Lactobacillus rhamnosus YW and S25; Lactobacillus gasseri S20; Streptococcus thermophilus S13 and S32) was investigated. The minimum inhibitory concentration (MIC) in most strains tested was found to be relatively high (from 6.25 mg.mL-1 to 12.50 mg.mL-1). The maximum concentration of polyphenols without any inhibitory effect (MCWI) ranges from 0.390 mg.mL-1 to 0.781 mg.mL-1. The results from the present study showed that among the tested lactic acid bacteria, Lactobacillus delbrueckii subsp. bulgaricus S19, Lactobacillus rhamnosus YW and Streptococcus thermophilus S13 had the best growth characteristics in a polyphenol-enriched culture medium. These strains had the highest MIC and MCWI values and could thus be used as starter cultures for polyphenol-fortified fermented milk. Practical applications: Polyphenol-enriched extracts from industrial plant by-products (waste) - distilled rose petals (by-products of rose oil production) and strawberry and bilberry press residues (by-products of fruit juice production) can help improve economic outcomes and solve environmental problems in the food industry. Consequently, the development of functional fermented milks with a combination of probiotic starter cultures and polyphenol extracts represents a positive research direction for the food industry.