# Bioconversion of Apple Pomace to _Meyerozyma guilliermondii_ and _Scheffersomyces stipitis_ Biomass
## 3 Results and Discussion
### The Results of the Yeast SCP Cultivation in the AP Hydrolysates  
The last but most important results of our experiment are presented in Table 8, where the biomass concentration after yeast cell cultivation in apple pomace hydrolyses is shown. \begin{table}
\begin{tabular}{l c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & **CA** & **SA** & **LA** & **FA** & **AA** \\  & & & **[g/L]** & & \\ \hline MgWE30 & 0.022 \(\pm\) 0.0008 & 0.012 \(\pm\) 0.0004 & 0.006 \(\pm\) 0.0002 & 0.074 \(\pm\) 0.0027 & 0.002 \(\pm\) 0.0001 \\ MgAE30 & 0.051 \(\pm\) 0.0021 & 0.094 \(\pm\) 0.0035 & 0.011 \(\pm\) 0.0004 & 0.045 \(\pm\) 0.002 & 0.004 \(\pm\) 0.0001 \\ MgWE50 & n.d. & 0.01 \(\pm\) 0.0003 & 0.029 \(\pm\) 0.0014 & 0.127 \(\pm\) 0.0057 & 0.004 \(\pm\) 0.0002 \\ MgAE50 & 0.007 \(\pm\) 0.0002 & 0.053 \(\pm\) 0.0017 & 0.03 \(\pm\) 0.0009 & 0.09 \(\pm\) 0.0037 & 0.006 \(\pm\) 0.0001 \\ SsAE30 & 0.066 \(\pm\) 0.0016 & 0.057 \(\pm\) 0.0023 & 0.021 \(\pm\) 0.001 & 0.102 \(\pm\) 0.0042 & 0.002 \(\pm\) 0.0001 \\ SsWE30 & 0.058 \(\pm\) 0.0026 & 0.049 \(\pm\) 0.0004 & 0.024 \(\pm\) 0.0006 & 0.097 \(\pm\) 0.0039 & 0.009 \(\pm\) 0.0004 \\ SsWE50 & 0.054 \(\pm\) 0.0205 & 0.045 \(\pm\) 0.0015 & 0.009 \(\pm\) 0.0002 & 0.057 \(\pm\) 0.0012 & 0.023 \(\pm\) 0.0006 \\ SsAE50 & 0.013 \(\pm\) 0.0002 & 0.031 \(\pm\) 0.0004 & 0.032 \(\pm\) 0.0011 & 0.134 \(\pm\) 0.0039 & 0.012 \(\pm\) 0.0005 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Organic acid content in the post-cultivation effluents. \begin{table}
\begin{tabular}{l c c} \hline \hline \multirow{2}{*}{**Sample**} & **GOH** & **EOH** \\  & & **[g/L]** & \\ \hline MgWE30 & n.d. & n.d. \\ MgAE30 & n.d. & 0.021 \(\pm\) 0.0006 \\ MgWE50 & n.d. & 0.014 \(\pm\) 0.0005 \\ MgAE50 & n.d. & 0.061 \(\pm\) 0.0023 \\ SsAE30 & n.d. & 0.022 \(\pm\) 0.0008 \\ SsWE30 & 0.008 \(\pm\) 0.0005 & 0.019 \(\pm\) 0.0009 \\ SsWE50 & 0.024 \(\pm\) 0.001 & 0.062 \(\pm\) 0.0011 \\ SsAE50 & n.d. & 0.113 \(\pm\) 0.0019 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Glycerol and ethanol content in the post-cultivation effluents. The final biomass concentration varied between 8.55 g/L and 16.29 g/L, depending on the hydrolysate and strain. For all samples, for yeast _S. stipitis_ and _M. guilliermondii_, more than 25% higher biomass multiplication was observed for hydrolyses obtained after acid pretreatment. It was observed that the _M. guilliermondii_ strain multiplied in the hydrolysed pomace more favourably than the _S. stipitis_ cells did. The highest biomass content was recorded for the MgAE50 sample (16.29 yeast g DM/L) when the _M. guilliermondii_ strain was cultivated in the medium prepared from apple pomace pretreated with 2% sulphuric acid and the subsequent enzymatic hydrolysis at 50 \({}^{\circ}\)C. This method of media preparation was also the most successful option for _S. stipitis_ cells, where the highest concentration of the biomass was observed in the sample SsAE50 at 14.63 g DM/L. However, while the use of 2% acid is considered acceptable from the eco-point of view, the result obtained for AP pretreated only with water and _Scheffersomyces stipitis_ strain (SsWE30) 13.03 \(\pm\) 0.19 g/L seems a very promising perspective toward the development of industrial-scale technology not based on the acid use and the subsequent need for its neutralisation and salt-containing post-cultivation effluent generation. Our results confirm enzymatic hydrolysis as desirable from a process efficiency point of view but disadvantageous from an economic point of view. Unfortunately, the combination of efficient enzymatic hydrolysis and economic viability has been the bottleneck of industrial implementations of biomass and ethanol production for decades.