# The Influence of Substrate and Strain on Protein Quality of _Pleurotus ostreatus_
## 3 Results and Discussion
### Amino Acid Composition
It has been also found that the nutritional value of _Agaricus brasiliensis_ protein is limited by its low isoleucine and valine content; _Flammulina veltipes_, _Pleurotus ergnigii_ and _Pleurotus ostreatus_ (black oyster) are deficient in leucine while _Agaricus bisporus_ (champignon and portobello), _Letinus edodes_, _Pleurotus digamor_ and _Pleurotus ostreatus_ (white oyster) meet the essential amino acid requirements according to the WHO/FAO/UNU reference standard for protein [16]. Obviously, the literature supports our findings for the high nutritional value of _P. ostreatus_ protein. The free amino acid (or non-protein amino \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Amino Acid (AA)**} & \multicolumn{3}{c}{_P. ostreatus_ Strains and Substrates \({}^{1}\)} \\ \cline{2-5}  & **150 WS** & **150 BOS** & **144 WS** & **144 BOS** \\ \hline Asp + Asn & 18.82 \(\pm\) 0.85 a & 25.34 \(\pm\) 6.74 a & 22.81 \(\pm\) 1.86 a & 24.85 \(\pm\) 0.86 a \\ Glu + Gln & 28.80 \(\pm\) 0.69 a & 39.92 \(\pm\) 6.32 b & 33.00 \(\pm\) 0.92 a & 39.60 \(\pm\) 3.05 b \\ Ser & 10.61 \(\pm\) 0.71 a & 13.60 \(\pm\) 1.39 b & 11.68 \(\pm\) 0.79 a & 13.56 \(\pm\) 1.30 b \\ His & 6.28 \(\pm\) 0.34 a & 8.66 \(\pm\) 0.17 b & 6.43 \(\pm\) 0.20 a & 8.28 \(\pm\) 0.80 b \\ Gly & 9.89 \(\pm\) 3.48 a & 13.59 \(\pm\) 4.30 a & 10.10 \(\pm\) 4.14 a & 12.01 \(\pm\) 3.30 a \\ Thr & 9.82 \(\pm\) 0.44 a & 13.04 \(\pm\) 1.93 b & 10.97 \(\pm\) 0.32 a & 12.45 \(\pm\) 1.22 b \\ Arg & 20.89 \(\pm\) 0.80 a & 30.58 \(\pm\) 1.94 b & 21.60 \(\pm\) 2.27 a & 27.70 \(\pm\) 1.37 b \\ Ala & 12.93 \(\pm\) 0.52 a & 18.28 \(\pm\) 1.85 b & 14.35 \(\pm\) 1.43 a & 17.72 \(\pm\) 1.52 b \\ Tyr & 5.74 \(\pm\) 0.25 a & 8.33 \(\pm\) 1.85 b & 6.81 \(\pm\) 1.10 a & 8.97 \(\pm\) 0.67 b \\ Val & 9.98 \(\pm\) 0.26 a & 13.48 \(\pm\) 1.88 b & 11.78 \(\pm\) 0.22 a & 13.54 \(\pm\) 0.48 b \\ Met & 3.55 \(\pm\) 0.32 a & 5.01 \(\pm\) 0.22 b & 3.97 \(\pm\) 0.17 a & 4.14 \(\pm\) 0.56 b \\ Cys-Cys & 8.90 \(\pm\) 0.98 a & 4.68 \(\pm\) 1.70 a & 3.61 \(\pm\) 1.74 a & 6.54 \(\pm\) 2.53 a \\ Phe & 8.43 \(\pm\) 0.24 a & 10.74 \(\pm\) 1.84 b & 9.64 \(\pm\) 0.51 a & 11.09 \(\pm\) 0.45 b \\ Ile & 8.34 \(\pm\) 0.56 a & 10.61 \(\pm\) 1.08 a & 9.64 \(\pm\) 0.88 a & 10.15 \(\pm\) 1.30 a \\ Leu & 14.71 \(\pm\) 1.81 a & 17.96 \(\pm\) 0.94 a & 17.11 \(\pm\) 3.35 a & 18.18 \(\pm\) 2.80 a \\ Lys & 24.77 \(\pm\) 6.67 a & 32.98 \(\pm\) 2.48 a & 30.82 \(\pm\) 12.51 a & 31.50 \(\pm\) 5.55 a \\ Sum & 202.45 \(\pm\) 4.46 a & 266.20 \(\pm\) 11.50 b & 224.32 \(\pm\) 6.78 a & 259.98 \(\pm\) 6.79 b \\ Essential AA & 106.77 \(\pm\) 11.44 a & 143.06 \(\pm\) 12.48 b & 121.96 \(\pm\) 20.43 a & 137.03 \(\pm\) 14.53 b \\ Essential AA (\%) & 52.70 \(\pm\) 0.11 a & 53.80 \(\pm\) 0.09 a & 54.30 \(\pm\) 2.40 a & 52.70 \(\pm\) 0.10 a \\ SAA \({}^{2}\) (Met + Cys-Cys) & 12.45 \(\pm\) 1.3 a & 9.69 \(\pm\) 1.92 a & 7.58 \(\pm\) 1.91 a & 10.68 \(\pm\) 3.09 a \\ AAA \({}^{3}\) (Phe + Tyr) & 14.17 \(\pm\) 0.49 a & 19.07 \(\pm\) 3.69 b & 16.45 \(\pm\) 1.61 a & 20.06 \(\pm\) 1.12 b \\ Sum of acidic amino acids (Asp + Glu) & 47.62 \(\pm\) 1.54 a & 65.26 \(\pm\) 13.06 b & 5.58 \(\pm\) 2.78 a & 64.45 \(\pm\) 3.91 b \\ Sum of basic amino acids (Lys + Arg + His) & 51.94 \(\pm\) 7.81 a & 72.22 \(\pm\) 5.49 b & 58.85 \(\pm\) 14.98 a & 67.48 \(\pm\) 7.72 b \\ \hline \hline \end{tabular}  
\({}^{1}\) Different lowercase letters denote significant (_p_ < 0.05) differences for each row. \({}^{2}\) SAA: sulfur-containing amino acids. \({}^{3}\) AAA: amino acids with aromatic side chain.  
\end{table} 
Table 2: Amino acid composition of the protein of flours from _P. ostreatus_ strains AMRL150 and 144 cultivated on different substrates (WS: wheat straw; BOS: barley and oat straw). Values (mg/g on a dry mass basis) are expressed as mean \(\pm\) standard deviation (n = 3). acid) content of mushrooms has also been investigated due to their important role in the taste and deliciousness of the product [45; 46].