# Cell Disruption and Hydrolysis of _Microchloropysis salina_ Biomass as a Feedback for Fermentation
## 3 Results and Discussion
### Composition of the Microalgal Biomass Hydrolysate  
Table 9 shows the sugar composition, as well as the phosphate and protein concentrations, of the microalgae hydrolysate produced on the 200 L scale after phosphate precipitation. Based on the sugar composition of \(M\). _salina_ grown in a nutrient-replete medium [12], microalgae biomass with a CDW concentration of 150 g L\({}^{-1}\) contained 24.2 g L\({}^{-1}\) glucose, 7.5 g L\({}^{-1}\) mannose, 2.6 g L\({}^{-1}\) galactose, and 1.9 g L\({}^{-1}\) rhamn, with the remaining carbohydrates amounting to 2.4 g L\({}^{-1}\). According to these values, only 15.2% of mannose could be solubilized with the applied hydrolysis protocol, whereas 58.5% saccharification efficiency of galactose was achieved. Nevertheless, considering an overall saccharification efficiency of 23%, sugar concentrations measured in the final microalgae hydrolysate are in accordance with these values. [PERSON] et al. [10] reported 40.8 g L\({}^{-1}\) glucose, 2.0 g L\({}^{-1}\) mannose, 4.3 g L\({}^{-1}\) galactose, and 13.3 g L\({}^{-1}\) protein in the microalgae hydrolysate of _Scenedesmus_ species starting with a CDW concentration of 250 g L\({}^{-1}\). Even though the total sugar concentration achieved by [PERSON] et al. [10] was much higher, the protein content was very similar to the concentration measured in this work. The amino acid concentration of the hydrolysate was not analyzed since the proteases used for biomass hydrolysis in this study were endopeptidase, which cannot break down peptides into their monomers. Considering the macromolecular com \begin{table}
\begin{tabular}{c c c} \hline \hline
**Component** & **Concentration, g L\({}^{-1}\)** & **Mass Fraction in Total Sugars, \%** \\ \hline Glucose & 5.32 & 65.9 \\ Mannose & 1.14 & 14.1 \\ Galactose & 1.52 & 18.8 \\ Rhamose & 0.08 & 1.0 \\ Xylose & 0.02 & 0.2 \\ \hline Total sugars & 8.08 & 100.0 \\ \hline Phosphate & 2.44 & – \\ Total protein and peptide & 13.4 & – \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Measured sugar composition, protein content, and phosphate concentration of the \(M\). _salina_ biomass hydrolysate. position of the dry _M. salina_ biomass, the measured 13.4 g L\({}^{-1}\) concentration of protein and peptide in the hydrolysate corresponds to 19.3% protein solubilization by hydrolysis of the initial biomass with 150 g L\({}^{-1}\) CDW concentration. The elemental composition of the microalgae hydrolysate after final processing is presented in Table 10. Based on these values, the microalgae hydrolysate produced contained 27.4 g L\({}^{-1}\) carbon, 16.6 g L\({}^{-1}\) nitrogen, and 0.8 g L\({}^{-1}\) phosphorus. This corresponds to a C/N ratio of 1.65 g g\({}^{-1}\) and a C/P ratio of 34.4 g g\({}^{-1}\). For comparison, yeast biomass grown without nutrient limitation has a C/N ratio of 5.37 g g\({}^{-1}\) and a C/P ratio of 55.4 g g\({}^{-1}\)[5], and synthetic media typically used for fermentation processes require similar amounts of these nutrients with respect to the carbon supplied [1; 58; 59]. Hence, these results suggest that the microalgal biomass hydrolysate could be used as a cultivation medium without any need for additional nitrogen or phosphorus supplementation. After phosphorus elimination, the C/P ratio became 2100 g g\({}^{-1}\). However, it should be noted that the C/P ratio was so high due to the high protein and peptide content despite the low sugar concentration. Assuming that sugars would be the only carbon source utilized by the microorganisms in a subsequent fermentation, the C/P ratio of the hydrolysate would be only 268 g g\({}^{-1}\). The mass fraction of carbon in the produced microalgae hydrolysate was determined to be 2.52%. This information allows for the calculation of the carbon solubilization efficiency as a measure of the overall hydrolysis efficiency.