## 3 Results  
### LAB Strain Selection  
The GGP proximal composition (expressed as % on d.m.) was as follows: proteins, 12.35 \(\pm\) 0.51; lipids 8.93 \(\pm\) 0.21; dietary fibers, 53.14 \(\pm\) 1.45; carbohydrates, 17.73 \(\pm\) 0.14; ash, 7.84 \(\pm\) 0.76. Moisture and a\({}_{w}\) were, respectively, 5.76 \(\pm\) 0.51% (\(w/w\)) and 0.3169 \(\pm\) 0.0012. Aiming at verifying the suitability of GPP as substrate for LAB growth, the 11 strains were inoculated in suspensions obtained with 10% GPP in water, with or without pH adjustment to 6.00 (initial pH of the GPP in water was 3.88 \(\pm\) 0.02, while TTA was 10.4 \(\pm\) 0.2 mL), with or without supplementations with glucose and/or yeast extract. No significant changes in pH and TTA were found for any of the conditions tested, while LAB cell density during the 24 h of incubation remained stable in conditions in which pH was corrected, while it decreased from 1 to 2 log cycles in all the others. Assuming a strong inhibition of microbial growth linked to the abundance of polyphenols and pH, the test was repeated in a substrate containing lower GPP concentration, corresponding to 5% and 2.5% (\(w/v\)) in water. In substrates containing 5% \(w/v\) GPP, with the initial correction of pH to 6.00, a slight pH decrease (up to 0.5) was found only for three of the eleven strains inoculated (_L. plantarum_ T0A10, H64, and _F. rossiae_ T0A16). When the percentage of pomace in the substrate was reduced to 2.5%, the \(\Delta\)pH value exceeded 0.5 units for all the strains inoculated. In particular, acidification was intense when glucose and yeast extract were used simultaneously as supplements. Under these conditions, the decrease in pH was, for _L. plantarum_ T0A10, _F. rossiae_ T0A16, and _L. plantarum_ H64, higher than 2.5 units. Based on these results, the substrate containing 2.5% of GPP, adjusted to pH 6.00, and with added glucose and yeast extract was considered suitable for the subsequent comparison of the fermentative performances of the LAB strains. The parameters obtained from the modeling of the acidification kinetics of the 11 strains are shown in Table 1. A, corresponding to the pH difference between the adaptation phase and the stationary phase, ranged from 2.878 and 2.361 (pH units), respectively for _F. rossiae_ T0A16 and _L. plantarum_ _18S9_. The strains having the highest A values were _F. rossiae_ T0A16 and _L. plantarum_ H64 and T0A10 (Table 1). The maximum acidification rate was between 0.475 and 0.311 \(\Delta\)pH/h. In particular, _P. pentosacetus_ H22, _F. rossiae_ T0A16 and _L. plantarum_ H64 showed Vmax values higher than 0.45. The adaptation phase was longer than 4 h for _L. plantarum_ T6B10, H18, H64, _P. pentosacetus_ H22, and _F. rossiae_ T0A16 and shorter than 3.4 h for all others. Cell densities reached by LAB strains in the pomace substrate are shown in Figure 1A. At the end of the 24 h incubation at 30 \({}^{\circ}\)C, the starters that presented the highest cell density were _L. plantarum_ T0A10 (9.57 \(\pm\) 0.12 log CFU/mL), _L. plantarum_ LB1 (9.47 \(\pm\) 0.11 log CFU/mL), and _L. plantarum_ H18 (9.41 \(\pm\) 0.10 log CFU/mL). Slightly lower values were found for _L. plantarum_ H64, 18S9 and T6B10, and _L. mesteroides_ 12 MM1. Significantly (\(p<0.05\)) lower cell densities were found for all the others, with _P. acidilactici_ 10 MM0 showing the lowest final cell density (7.00 \(\pm\) 0.01 log CFU/mL) (Figure 1A).