## 3 Results
#### 3.1.1 Nutrients (Proteins and Carbohydrates)  
The protein and carbohydrate values for each extraction condition are shown in Table 2. As can be seen in the table, the protein values ranged from 4.14 to 6.10 g/100 g of dry matter, being the optimal conditions for the maximal protein recovery (24.4 min, 20 \({}^{\circ}\)C and pH 8.5) obtained under this condition: 5.96 g of proteins/100 g dry matter. On the other hand, the values for the carbohydrates ranged from 1.39 g/100 g dry matter to 2.52 g/100 g dry matter. In this case, the optimal conditions for the highest carbohydrate extraction were 30 min, 50 \({}^{\circ}\)C and a pH of 8.5, obtaining 2.53 g of carbohydrates/100 g dry matter.  
The influence of the extraction time, temperature and pH for the proteins and carbohydrates is shown in Figures 1 and 2, respectively. Regarding the protein, as can be seen in Figure 1, although it seems that both the temperature and time affected protein extraction, the ANOVA analysis revealed that these changes were not significant (\(p\) = 0.0553 for temperature and 0.1690 for the time of extraction). The pH did not show any significant influence (\(p\) = 0.6355). On the contrary, regarding the carbohydrate extraction, the temperature clearly influenced the extraction (\(p\) = 0.0040), while the pH and time of extraction did not have a significant influence (\(p\) = 0.2954 and 0.6061, respectively). Regarding the temperature, as can be seen in Figure 2, an important increase in carbohydrate extraction  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Run \#**} & **Time of Extraction** & **Temperature** & **Proteins** & **Carbohydrates** \\  & **(min)** & **(\({}^{\circ}\)C)** & **pH** & **(g/100 g Dry Matter)** & **(g/100 g Dry Matter)** \\ \hline
1 & 15 & 20 & 7 & 5.19 & 1.48 \\
2 & 30 & 20 & 8.5 & 6.10 & 1.56 \\
3 & 30 & 20 & 5.5 & 5.37 & 1.79 \\
4 & 0.5 & 20 & 8.5 & 4.74 & 1.39 \\
5 & 0.5 & 20 & 5.5 & 5.47 & 2.16 \\
6 & 15 & 35 & 7 & 5.03 & 2.13 \\
7 & 15 & 35 & 7 & 4.80 & 2.01 \\
8 & 15 & 35 & 8.5 & 5.14 & 2.33 \\
9 & 15 & 35 & 5.5 & 5.40 & 2.03 \\
10 & 30 & 35 & 7 & 4.28 & 1.90 \\
11 & 0.5 & 35 & 7 & 4.71 & 1.91 \\
12 & 15 & 50 & 7 & 5.34 & 2.10 \\
13 & 30 & 50 & 8.5 & 5.23 & 2.52 \\
14 & 30 & 50 & 5.5 & 4.69 & 2.03 \\
15 & 0.5 & 50 & 8.5 & 4.14 & 1.84 \\
16 & 0.5 & 50 & 5.5 & 4.95 & 2.22 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Proteins and carbohydrates (g/100 g dry matter) obtained after ultrasound-assisted extraction at different times, temperatures and pH levels.  
was found, obtaining the maximum yield at temperatures between 45-50 \({}^{\circ}\)C. This fact can be explained due to the modification of the integrity of the cell wall after the increase in temperature, then the solvent solution contact with the intracellular compounds was facilitated, thus improving their extraction [27].  
In a similar way, other authors did not observe any significant influence of these parameters for protein extraction from microalgae. In this sense, [PERSON] et al. [28] did not find a significant effect from the sonication time, temperature or pH when extracting proteins from Spirulina platensis. Moreover, the same authors reported a significant and positive influence of the temperature for carbohydrate extraction. On the other hand, [PERSON] et al. [29] optimized the UAE of protein extraction from Spirulina microalgae, using a response surface method with a central composite design. They found that the extraction time (10-120 min) and pH (9-11) had a significant effect on protein solubilization. Finally, [PERSON] et al. [19] also reported that ultrasound treatment increased the protein extraction from Chlorella vulgaris, especially at a basic pH (in a NaOH medium).