# Cell Disruption and Hydrolysis of _Microchloropysis salina_ Biomass as a Feedback for Fermentation
Nonetheless, mechanical cell disruption methods are energy intensive, increasing production costs. In order to determine if a lower-cost alternative is possible without compromising on the disintegration efficiency, acidic hydrolysis of the undisrupted cells followed by enzymatic hydrolysis was also performed. Enzymatic hydrolysis of the disrupted microalgae cells aimed for maximum saccharification efficiency of the carbohydrates in the microalgal biomass. The enzymes were selected based on the cell wall composition of _Microchloropsis_ species targeting the main constituents of the cell wall, namely glucose and mannose [12; 17]. For process scalability, combinations of various commercially available enzyme mixtures were tested for biomass hydrolysis. _M. salina_ biomass grown under nutrient-replete conditions has around 26% (\(w/w\)) carbohydrates and 50% (\(w/w\)) proteins [12], both of which could be converted into valuable carbon sources that can be utilized in a fermentation process. This corresponds to a theoretical maximum of 65 g L\({}^{-1}\) sugar concentration in a microalgal biomass hydrolysate produced using concentrated biomass with 250 g dry cell weight per liter. Although sugar concentrations around 20-50 g L\({}^{-1}\) are considered typical for the waste streams or biomass hydrolyses generally used as a substrate for fermentation [20; 21; 22; 23], such a low concentration of the carbon source is still significantly diluted in comparison to synthetic media used in industrial processes. Therefore, it is essential to keep the initial biomass density as high as possible to maximize the sugar concentration in the resulting biomass hydrolysate. Consequently, this study used high-density whole-cell microalgae paste with a 100-250 g L\({}^{-1}\) solids content as the starting material. A major advantage of using biomass hydrolysate as a cultivation medium is its high content of nitrogen and phosphorus in addition to carbon. These essential nutrients are required for unlimited microbial growth and are introduced into the synthetic growth media typically in the form of ammonia and phosphate salts, similarly to the use of a fertilizer in agriculture. Therefore, this study conducted an elemental analysis of the microalgal biomass hydrolysate to assess its suitability as a growth medium without the addition of these salts. Nevertheless, some fermentation processes, such as microbial oil production by oleaginous microorganisms or hydrogen production by photosynthetic microbes, require a nutrient deficiency in the cultivation medium to induce the metabolism to produce the desired product. To investigate the feasibility of using microalgae hydrolysate in such fermentation processes, phosphorus depletion of the biomass hydrolysate was also explored. Since using a precipitating agent is an easy and effective method commonly used in wastewater treatment facilities on large scales [24], phosphorus elimination using FeCl\({}_{3}\) as a precipitating agent was the preferred method in this work. This study focuses on _M. salina_ biomass hydrolysis by employing various mechanical and chemical cell disruption strategies in combination with enzymatic hydrolysis and aims to explore the potential of the resulting hydrolysate as a feedstock for fermentation. The analysis focuses mainly on the monosaccharide composition and the total protein and peptide content since these are the carbon sources that microorganisms can utilize in a subsequent fermentation.