Stevia rebaudiana leaves fermented by Lactobacillus plantarum exhibit resistance to microorganisms and cancer cell lines in vitro: A potential sausage preservative

Natural preservatives are causing a rethinking of current preservation means. As a sweetener resource, exploitation of Stevia rebaudiana leaves (SRLs) is still restricted due to human conventional cognition. Herein, Lactobacillus plantarum fermented SRLs containing diverse free secondary metabolites derived from microbial deglycosylation and bioenzymatic decomposition were investigated. The apparent resistance to typical foodborne bacteria (Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Pseudomoas aeruginosa, Bacillus amyloliquefaciens) by fermented SRLs and their extracts were validated. The metabolite diversity and in-depth organic solvent extraction gave the possibilities for better antimicrobial actions, anti-HepG2/SGC-7901 cells in vitro in contrast with aqueous extract of unfermented SRLs. Crucially, compound identification and attribution revealed that fermentation products may be maximally contributing to antimicrobial and antitumor mechanisms rather than intrinsic plant and/or microbial components. Additionally, pork sausage models with 15 g/kg ethyl acetate extract as a preservative candidate presented preferred storage characteristics (21 days and 37 °C) compared to those without ethyl acetate extract, e.g. the minimal total plate count (3.86 ± 0.27 log CFU/g), peroxsignide value (8.02 ± 0.92 meq/kg), and acid value (2.01 ± 0.04 (KOH)/(mg/g)).