## 4 Discussion  
The main objective of the present study concerned the application of a biotechnological procedure suitable to utilize CSC, targeting the reduction of gossypol. According to some preliminary experiments that we performed, and in accordance with the existing literature, it was shown that the addition of LCP, which is a by-product rich in nitrogen, promotes the conditions that facilitate mycelium's colonization and, therefore, the application of the SSF process. Therefore, according to the latter, a substrate was prepared by adding LCP at a ratio of 20% \(w/w\) since the specific addition displayed the best results. The final goal concerned the evaluation of SSF's technique on a substrate consisting of a CSC-LCP (80-20% \(w/w\)) mixture, focusing on the reduction of its gossypol content and the parallel enhancement of its nutritional value in order to be transformed into a suitable material that could potentially be used as a feed supplement in animals' diets. The nutritional value of the examined substrate was improved after employing the SSF procedure, which is attested by the evaluation of its physicochemical parameters, especially for its proteins and 1,3-1,6 \(\beta\)-glucans content. Moisture is a very important attribute that affects SSF's efficiency, since it is closely associated with nutrient availability [22]. In specific, a reasonable presence of moisture exerts a beneficial effect on SSF by promoting fungal growth, nutrient transfer, and enzymatic activity, whereas a high moisture content is capable of mitigating the substrate's porosity, limiting oxygen's transfer, and facilitating possible contamination, since the employed substrate forms an ideal environment for the growth of unfavorable microorganisms. On  
Figure 2: Representative chromatogram of Total Gossypol (R.T. \(\approx\) 10.1) at Day 0 (chrom. A) and at the end of the SSF procedure (Day 11) (chrom. B). the other hand, a low moisture content is an aggravating factor for the successful implementation of the SSF process since accessibility and solubility are confined. Hence, the employed microorganism is not able to absorb the required amounts of the necessary nutrients, resulting in poor fungal growth [23]. It must be noted however that at the end of the SSF procedure, moisture content was found to be increased. This can be rationalized considering that during SSF implementation, the water balance is affected by several factors such as the presence of required water, which is essential for starch's hydrolysis, the production of metabolic water, the absorption of intracellular water through biomass synthesis, and the evaporation of water assisted by the metabolic heat [24]. According to [PERSON] et al. [25], a moisture content of 60% is considered the optimum value for a successful SSF application. Our results are in line with previous literature reports, since herein the moisture content reached 68% at the end of the SSF procedure. One of the most common strategies adopted for the efficient utilization of lignocellulosic materials includes the application of SSF by employing suitable microorganisms, namely, white-rot fungi. The latter is capable of consuming the available nutrients included in the respective materials, targeting the production of new organic compounds that can be transferred to the whole biomass through fungal activity, thus enhancing their nutritional value [26]. _P. ostreatus_ displays the capability to act as a lignocellulosic degradation agent since it is composed of extracellular enzymes that can modify the lignocellulosic materials. In the present work, the amount of Crude Fiber Substances (CFS) was increased during the process implementation. A possible explanation that justifies the increased level of CFS is connected with the parallel increase in cellulose content [10]. Furthermore, CFS's elevated presence could probably be rationalized by microbial activity.