# Cell Disruption and Hydrolysis of _Microchloropysis salina_ Biomass as a Feedback for Fermentation  
[PERSON]  
1 Chair of Biochemical Engineering, School of Engineering and Design, Technical University of Munich, 85748 Garching, Germany; [EMAIL_ADDRESS] (A.K. ); [EMAIL_ADDRESS] (T.P. ); [EMAIL_ADDRESS] (E.K. ); [EMAIL_ADDRESS] (L.G. ); [EMAIL_ADDRESS] (P.)  
[PERSON]  
1 Chair of Biochemical Engineering, School of Engineering and Design, Technical University of Munich, 85748 Garching, Germany; [EMAIL_ADDRESS] (A.K. ); [EMAIL_ADDRESS] (T.P. ); [EMAIL_ADDRESS] (E.K. ); [EMAIL_ADDRESS] (L.G. ); [EMAIL_ADDRESS] (P.)  
[PERSON]  
1 Chair of Biochemical Engineering, School of Engineering and Design, Technical University of Munich, 85748 Garching, Germany; [EMAIL_ADDRESS] (A.K. ); [EMAIL_ADDRESS] (T.P. ); [EMAIL_ADDRESS] (E.K. ); [EMAIL_ADDRESS] (L.G. ); [EMAIL_ADDRESS] (P.)  
[PERSON]  
1 Chair of Biochemical Engineering, School of Engineering and Design, Technical University of Munich, 85748 Garching, Germany; [EMAIL_ADDRESS] (A.K. ); [EMAIL_ADDRESS] (T.P. ); [EMAIL_ADDRESS] (E.K. ); [EMAIL_ADDRESS] (L.G. ); [EMAIL_ADDRESS] (P.)  
[PERSON]  
1  
[PERSON]  
Microalgae are a promising biomass source as a feedstock because of their capability to fixate CO\({}_{2}\) very efficiently [7] and grow with wastewater streams [8; 9]. Moreover, they can grow much faster than higher plants, require no arable land, and demand less freshwater use. Utilization of microalgae hydrolysate as a fermentation medium has already been demonstrated to be feasible [10; 11]. Although some microalgae are oleaginous microorganisms that can produce lipids, they have relatively low lipid productivity, resulting in the low cost-competitiveness of microalgae lipid production. It has been previously shown that microalgae cultivated photoautotrophically without nutrient limitation (nitrogen, phosphorous) can achieve significantly higher biomass productivity compared to lipid production under growth-limiting conditions [12]. Therefore, it could be more beneficial to cultivate the microalgae without nutrient limitation to be used as feedstock for fermentation processes after hydrolysis. The marine microalgae _Microchloropsis salina_ is known to achieve relatively high growth rates of 0.03 h\({}^{-1}\), with an optimum salinity of 35 g L\({}^{-1}\) at pH 7.5-8.0 [13]. These conditions naturally limit the presence of contaminants in an open culture, making it possible to use simple open cultivation systems to economically produce microalgae biomass photoautotrophically as a raw material for industrial use [14]. Additionally, the high salinity requirement of the microalgae culture enables the use of seawater as the cultivation medium, reducing freshwater consumption. _M. salina_ is a single-cell species not prone to aggregate or biofilm formation [15], presenting another advantage for easy cultivation. Furthermore, it has been demonstrated recently that this strain can achieve high areal biomass productivity of 27 g m\({}^{-2}\) d\({}^{-1}\) (dry mass) and up to 100% CO\({}_{2}\) fixation efficiency when cultivated in open thin-layer cascade photobioreactors [7]. Given these benefits associated with biomass production, _M. salina_ was chosen as the source of biomass for the production of microalgal biomass hydrolysate in this study. Marine microalgae have rather complex and structurally stable cell walls, which are hard to disrupt [6; 16; 17]. Therefore, various mechanical and chemical cell disruption methods are examined in this study. An efficient cell disruption increases the availability of the substrates for the subsequent enzymatic hydrolysis and is, therefore, crucial for the efficient hydrolysis of the whole-cell microalgae biomass. For the mechanical disruption of highly dense _M. salina_ biomass, ultrasonication, bead milling, and high-pressure homogenization were investigated. These methods were selected specifically for their effectiveness with microalgae [18] and applicability in continuous processes on an industrial scale [19].