## 4 Discussion  
In this study, the oyster mushroom is cultivated in the BSG and wheat bran mixture, and the cultivation residue is used as an ingredient for baking bread. The cultivation residue had high fibre, beta-glucan and niacin content. It also contained protein, thiamine, riboflavin and pyridoxine. The development of bread from 50% cultivation residue and 50% wheat flour resulted in a golden-brown bread with different sensory characteristics in terms of colour, texture, taste and smell compared to white bread. Although the bread prototype's sensory characteristics scores differed from white bread, its overall liking and acceptability scores were not significantly different from white bread. According to the findings of this study, the biological efficacy of oyster mushroom in the BSG and wheat bran mixture can be considered good, as the biological efficacy of this type of mushroom varies between less than 30% and more than 100%, depending on the substrate [29]. For example, the oyster mushroom cultivation in maize stalks and wheat straw had a biological efficiency of 27% and 115%, respectively [29]. It is worth mentioning that [PERSON], [PERSON] and [PERSON] [10] calculated the biological efficacy after harvesting one flush based on the weight of dried oyster mushrooms; therefore, their results cannot be directly compared to our findings, despite the same substrate being used. In addition to the substrate type, the biological efficiency depends on the number of flushes and substrate supplementation. The biological efficiency of oyster mushroom in sugarcane bagasse after harvesting one flush was 50% but increased to 115% after harvesting three flushes [30]. The substrate supplementation with other lignocellulosic materials may also improve the biological efficacy [31]. In this study, total biological efficacy was calculated after harvesting two flushes of mushrooms, and BSG was supplemented with 45% wheat bran. Some of the cultivation residue's properties, such as a pleasant smell, can be due to the presence of mycelium. Oyster mushroom mycelium contains diverse aromatic compounds, and its olfactory impact is related to _Pleurotus_ aroma [32]. The main aromatic compound in oyster mushroom mycelium is octan-3-one, followed by octan-3-ol [32]. The octan-3-one odour has been described as sweet, fruity or mildewy and is responsible for the lemon-like odour [32]. The octan-3-ol contributes to the hazelnut and herbaceous sweet note [32]. Other aromatic compounds are oct-1-en-3-one (cooked mushroom note), octanal (honey-orange like odour) and octanol (orange-rose like odour) [32]. The _Pleurotus_ aroma is probably responsible for the bread prototype's aromatic smell, which is one of the sensory characteristics that differentiated this bread from the white bread. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Bread Prototype** & **White Bread** & \\  & **Median (Min–Max)** & **Median (Min–Max)** & _p_-Value \({}^{*}\) \\ \hline Appearance liking & 4.00 (3–5) & 4.00 (3–5) & 0.792 \\ Texture liking & 3.00 (2–5) & 4.00 (2–5) & 0.366 \\ Flavour liking & 3.00 (1–4) & 4.00 (2–5) & 0.019 \\ Aroma liking & 3.00 (1–4) & 4.00 (2–5) & 0.072 \\ Overall liking & 3.00 (2–5) & 4.00 (2–5) & 0.141 \\ Acceptability & 3.00 (2–5) & 4.00 (3–5) & 0.248 \\ \hline \hline \end{tabular} \({}^{\dagger}\) The scores were from 0 to 5 (0 = not present, 1 = very low, 2 = low, 3 = neither high nor low, 4 = high, 5 = very high). \({}^{*}\)_p_-value for comparison between bread prototype and white bread assessed by the Wilcoxon Signed Ranks Test.  
\end{table} 
Table 3: The median scores \({}^{1}\) for the liking and acceptability of the bread prototype and white bread, and the comparison of these two types of bread (_n_ = 11). The nutritional assessment of cultivation residue showed an increase in the crude protein from 18% in the initial substrate to 23% in the cultivation residue (after the second flush harvest). In contrast, data from amino acid analyses demonstrated a decrease in protein content (from 13.7% to 10.8%).