## 2 Materials and Methods  
### Isolation and Identification of LAB from Mango Peel  
Mango fruits (_Mangifera indica_ L., variety Keitt) were harvested from \"Azienda Agricola Tripodo-Collura\" in Acquedolci, Sicily, Italy (38 deg03'27'' N-14 deg36'38'' E 50 m s.l.m). The peel was manually removed using stainless steel knives and then stored at -20 degC until microbiological analysis.  
Presumptive LAB were isolated from the mango peel at the highest cell densities, using the following specific media for plate counting: De Man-Rogosa-Sharpe (MRS), M17, and sourdough bacteria (SDB). Incubation occurred at 30 degC for 48 h anaerobically for MRS and M17 plates, while SDB plates were incubated aerobically under the same conditions. To maximize LAB biodiversity, at least four colonies with similar appearances in terms of shape, size, colour, edge, surface characteristics, and elevation were isolated. All isolates underwent preliminary characterization through Gram staining following the method described by [PERSON] [16] and a catalase test as reported by [PERSON] et al. [17]. Only Gram-positive cultures negative for catalase expression were further purified through successive sub-culturing and stored in glycerol stocks at -80 degC. The acidification kinetics were assessed following the method described by [PERSON] et al. [18], employing a sterile semolina extract (SSE) at 20% concentration as the growth medium. LAB cultures were propagated, washed and inoculated into SSE without maltose. The pH decrease was monitored at 0, 2, 4, 6, 8 and 24 h after inoculation.  
The LAB isolates underwent genetic characterization. Overnight cultures were grown in their optimal growth media at 30 degC, and genomic DNAs was extracted from pelleted cells using the InstaGene Matrix kit (Bio-Rad, Hercules, CA, USA) following the manufacturer's instructions. Crude cell extracts served as templates for PCR. Random amplification of polymorphic DNA (RAPD)-PCR analysis was performed to differentiate the isolates at the strain level. Specifically, the M13 primer, as described by [PERSON] et al. [19], was used, and the resulting amplicons were separated and visualized according to [PERSON] et al. [20]. RAPD profiles were analysed using Gelcompar II software, version 6.5 (Applied-Maths, Sint-Martens-Latem, Belgium). The strains were identified at the species level by 16S rRNA gene sequencing. PCR reactions were performed using the primers fD1 (5'-AGAGAGTTTGATCCTGGCTCAG-3')/rD1 (5'-AAGAGGTGATCCAGCC-3') as described by [PERSON] et al. [21]. The resulting PCR products had a molecular size of about 1600 bp, which was confirmed using agarose gels. After purification with the QIAquick purification kit (Quiagen S.p.a. Milan, Italy), the amplicons were sequenced using the same primers used for PCR amplification at AGRIVET (University of Palermo, Italy). The obtained sequences were then compared with those available in the GenBank/EMBL/DDBJ [[https://www.ncbi.nlm.nih.gov](https://www.ncbi.nlm.nih.gov)]([https://www.ncbi.nlm.nih.gov](https://www.ncbi.nlm.nih.gov)) (accessed on 10 June 2024) and EzTaxon-e databases [[https://eztaxon-e.ezbiocloud.net](https://eztaxon-e.ezbiocloud.net)]([https://eztaxon-e.ezbiocloud.net](https://eztaxon-e.ezbiocloud.net)) (accessed on 10 June 2024).