# Cell Disruption and Hydrolysis of _Microchloropysis salina_ Biomass as a Feedback for Fermentation
## 4 Conclusions  
The aim of this study was to investigate the potential of _M. salina_ biomass as a feedstock for fermentation by examining various cell disruption and hydrolysis methods. For the marine microalgae _M. salina_, the most effective cell disruption method was determined to be bead milling with 2 mm stainless-steel beads. Despite the high degree of cell disruption, enzymatic hydrolysis of the microbial biomass yielded a saccharification efficiency of around 20-25%. Even though the sugar concentration of the resulting hydrolysate was low for a fermentation medium (<10 g L\({}^{-1}\)), it would be possible to concentrate the hydrolysate be evaporation, for example, using a thin-film evaporator, to achieve higher sugar concentrations. Elemental analysis of the _M. salina_ biomass hydrolysate showed that the microalgae hydrolysate could be used as a cultivation medium without any need for additional nitrogen or phosphorus supplementation. The hydrolysate produced was rich in phosphates as well as nitrogen due to a high content of proteins and peptides. The use of microalgal biomass hydrolysate in fermentation processes requiring phosphorus limitation was also shown to be feasible through phosphorus depletion using FeCl\({}_{3}\) as a precipitating agent. All in all, this study presents useful insights into the disruption and enzymatic hydrolysis of marine microalgae species, as well as their potential as a feedstock for fermentation. However, the low-carbohydrate saccharification yield achieved with _M. salina_ makes it a \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{4}{c}{**Mass Fraction of the Element, \%**} & \multicolumn{2}{c}{**Ratio, g g\({}^{-1}\)**} \\ \cline{2-7}
**Hydrolysate** & **C** & **H** & **N** & **S** & **P** & **C/N** & **C/P** \\ \hline After hydrolysis & 2.76 & 9.90 & 1.67 & 0.00 & 0.08 & 1.65 & 34.4 \\ After P elimination & 2.52 & 10.84 & 1.65 & 0.00 & 0.00 & 1.53 & 2100.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Elemental composition of the _M. salina_ biomass hydrolysate. poor choice for use as feedstock. Alternatively, other microalgae strains that are richer in carbohydrates and easier to disrupt, such as the members of _Porphyridium_ and _Scenedesmus_ genera [(40; 60)], could be preferred. This would decrease the cost of the energy-intensive mechanical cell disruption and allow for more efficient biomass hydrolysis and, thus, for a higher sugar concentration in the resulting microalgal biomass hydrolysate. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app14219667/s1](https://www.mdpi.com/article/10.3390/app14219667/s1)]([https://www.mdpi.com/article/10.3390/app14219667/s1](https://www.mdpi.com/article/10.3390/app14219667/s1)), Figure S1: Variation of the centrifugation duration for phosphate precipitation with a constant Fe:P stoichiometric ratio of 1.5; Table S1: Stepwise phosphate precipitation of microalgae hydrolysate on a 1 L scale; Table S2: Stepwise phosphate precipitation of microalgae hydrolysate on a 50 mL scale. Conceptualization, A.K., T.B. and D.W.-B. ; methodology, validation, formal analysis, and investigation, A.K., T.P., E.K., L.G. and P.; writing--original draft preparation, A.K. ; writing--review and editing, T.B. and D.W.-B. ; visualization, A.K. ; supervision, D.W.-B. ; project administration, T.B. and D.W.-B. ; funding acquisition, T.B. and D.W.-B. All authors have read and agreed to the published version of the manuscript. This research was funded by the German Federal Ministry of Education and Research (BMBF, Berlin, Germany), under grant number 03 SF0577A. Not applicable. The data presented in this study are available on request from the corresponding author. We thank [PERSON] and [PERSON] at the Analytical Department of the TUM Catalysis Research Center (CRC) for performing the elemental analysis. The support of [PERSON] by the TUM Graduate School (Technical University of Munich, Germany) is acknowledged as well. The authors declare no conflicts of interest.