# Exploitation of Three Non-Conventional Yeast Species in the Brewing Process
## 3 Results
### Fermentation Trials with the Selected Non-Saccharomyces Yeasts  
#### 3.2.1 Evaluation of Population Dynamics  
The growth kinetics of _L. thermotolerans_ in pure and in mixed fermentation are reported in Figure 1. The _S. cerevisiae_ US-05 pure cultures achieved \(10^{8}\) CFU/mL after four days of fermentation (maximum viable cells) and maintained \(10^{7}\) CFU/mL until the end of the fermentation. Differently, in the mixed cultures with the inoculation ratio of 1:1 (Figure 1a), _S. cerevisiae_ US-05 reached a lower biomass, achieving only \(10^{7}\) CFU/mL on the fourth day of fermentation. The same trend was also exhibited for _S. cerevisiae_ US-05 with the inoculation ratios of 1:10 and 1:20 (Figure 1b,c). _S. cerevisiae_ was not inhibited at all in the inoculation ratios and completed fermentation as showed by residual sugar and ethanol content in the final beers (Table 2). _L. thermotolerans_ in mixed fermentation at the 1:10 and 1:20 inoculation ratios showed a biomass evolution comparable with that of the pure culture, while at the 1:1 inoculation ratio, _L. thermotolerans_ showed a very limited increase in biomass compared with that exhibited by _S. cerevisiae_ under the same conditions (Figure 1a). Under these conditions, both strains suffered a mutual inhibition but showed no differences compared with the control trial (US 05 strain) (Table 2). The biomass evolution of the _S. cerevisiae_ and _Z. florentina_ mixed fermentations at the 1:1 inoculation ratio (Figure 2a) exhibited a similar growth kinetic (with a slight prevalence of _S. cerevisiae_), and they reached a maximum cell concentration of \(10^{7}\) mL/L after four days, showing a reciprocal inhibition compared with pure cultures. \begin{table}
\begin{tabular}{l c c} \hline \hline \multirow{2}{*}{**Strains**} & **Total CO\({}_{2}\) g Evolved** & **Fermentation Rate** \\  & **(20 Days)** & **(g CO\({}_{2}\)/Day)** \\ \hline _L. thermotolerans_ DiSVA 322 & 3.87 \(\pm\) 0.05 & 0.31 \(\pm\) 0.05 \\ _L. thermotolerans_ DISVA 324 & 3.49 \(\pm\) 0.04 & 0.16 \(\pm\) 0.03 \\ _L. thermotolerans_ DiSVA 325 & 2.04 \(\pm\) 0.37 & 0.13 \(\pm\) 0.06 \\ _L. thermotolerans_ DiSVA 326 & 2.13 \(\pm\) 0.20 & 0.10 \(\pm\) 0.05 \\ _L. thermotolerans_ DiSVA 327 & 3.60 \(\pm\) 0.08 & 0.16 \(\pm\) 0.05 \\ _W. anomalous_ DiSVA 2 & 1.68 \(\pm\) 0.40 & 0.22 \(\pm\) 0.09 \\ _W. anomalous_ DiSVA 45 & 1.30 \(\pm\) 0.21 & 0.17 \(\pm\) 0.06 \\ _W. anomalous_ DiSVA 45 & 1.84 \(\pm\) 0.12 & 0.23 \(\pm\) 0.07 \\ _W. anomalous_ DiSVA 56 & 1.58 \(\pm\) 0.06 & 0.16 \(\pm\) 0.03 \\ _W. anomalous_ DiSVA 336 & 1.27 \(\pm\) 0.03 & 0.18 \(\pm\) 0.03 \\ _W. anomalous_ DiSVA 355 & 1.47 \(\pm\) 0.12 & 0.19 \(\pm\) 0.04 \\ _W. anomalous_ DiSVA 356 & 1.58 \(\pm\) 0.35 & 0.21 \(\pm\) 0.10 \\ _W. anomalous_ DiSVA 359 & 1.40 \(\pm\) 0.25 & 0.18 \(\pm\) 0.02 \\ _W. anomalous_ DiSVA 383 & 1.69 \(\pm\) 0.07 & 0.22 \(\pm\) 0.05 \\ _W. anomalous_ DiSVA 384 & 1.45 \(\pm\) 0.09 & 0.20 \(\pm\) 0.06 \\ _W. anomalous_ DiSVA 385 & 1.71 \(\pm\) 0.14 & 0.20 \(\pm\) 0.06 \\ _W. anomalous_ DiSVA 386 & 1.82 \(\pm\) 0.11 & 0.23 \(\pm\) 0.06 \\ _Z. florentina_ DiSVA 262 & 3.41 \(\pm\) 0.12 & 0.34 \(\pm\) 0.02 \\ _Z. florentina_ DiSVA 263 & 3.66 \(\pm\) 0.13 & 0.32 \(\pm\) 0.06 \\ _Z. florentina_ DiSVA 264 & 2.33 \(\pm\) 0.14 & 0.14 \(\pm\) 0.03 \\ _Z. florentina_ DiSVA 309 & 2.52 \(\pm\) 0.21 & 0.23 \(\pm\) 0.05 \\ _Z. florentina_ DiSVA 310 & 1.14 \(\pm\) 0.36 & 0.16 \(\pm\) 0.05 \\ _Z. florentina_ DiSVA 311 & 1.16 \(\pm\) 0.09 & 0.23 \(\pm\) 0.09 \\ _Z. florentina_ DiSVA 312 & 1.84 \(\pm\) 0.14 & 0.27 \(\pm\) 0.07 \\ _Z. florentina_ DiSVA 317 & 0.68 \(\pm\) 0.31 & 0.01 \(\pm\) 0.01 \\ _S. cerevisiae_ US-05 & 4.61 \(\pm\) 0.05 & 0.65 \(\pm\) 0.04 \\ \hline \hline \end{tabular} Data are the means \(\pm\) standard deviations. CO\({}_{2}\) g evolved after 20 days of fermentation (in 100 mL of 10% malt extract). Fermentation rate: CO\({}_{2}\) g/day (over the first 6 days of fermentation).  
\end{table} 
Table 1: Fermentation parameters of different non-conventional yeasts on malt extract.