## 4 Discussion
In specific, during the SSF procedure, the employed microorganisms display the ability to convert into assimilable forms the substrate's molecules in order to fulfill their biological requirements. Peptidoglycan, which is included among these assimilable molecules, is a polysaccharide that is considered one of the main components of the bacterial wall. At the end of the SSF procedure, the respective microorganism is not separated from the biomass, affording a possible increase in CFS content as a consequence of the respective molecules' conversion into peptidoglycan via the biological action of involved microorganism [27; 28]. The observed reduction in cellulose content is presumably justified considering the different ratios of fiber fractions that are present in the initial raw materials. Additionally, cellulose's reduction is possibly associated with the nutritional composition of the studied substrate since the latter displays the potential to provide the participating microorganism with the required nutrients such as N, P, and K, leading to an extensive degradation [29]. The enzymatic activity of _P. ostreatus_ is responsible for the reduction of the unwanted lignin content, probably due to the action of lignin-modifying enzymes [30]. Furthermore, according to [PERSON] and [PERSON] [30], Pleurotus spp. can be characterized as selective degraders since they degrade lignin more efficiently as compared to cellulose. TSS and RSS constitute an energy source for the employed microorganism. They observed that the content at Day 11 was possibly correlated to the excessed secretion of enzymes that are used to facilitate the degradation process [31]. According to [PERSON] et al. [32], the elevated ash content during the SSF process is presumably connected with the enzymatic activity of _P. ostreatus_, which facilitates the reduction of organic matter on the investigated substrate. Moreover, it must be noted that the increased ash presence is of high importance since it can be considered a marker indicating a significant mineral content [33]. The nutritional value of mushrooms is highlighted by the presence of various bioactive compounds, including 1,3-1,6 \(\beta\)-glucans, which are well known for their health-beneficial effects on both humans and animals. Herein, the concentration of 1,3-1,6 \(\beta\)-glucans increased considerably at the end of the procedure; an outcome connected with _P. ostreatus_' biochemical activity that transforms a substrate's nutrients into organic compounds. The protein content of the investigated substrate constitutes the most significant attribute. SSF has the potential to act as a valuable procedure since its efficacy can be attestedby the bioconversion of the examined substrate into protein-enriched material. Considering our results, protein content increases during the SSF procedure, presumably as a result of the excessed nitrogen assimilation in terms of the aerobic fermentation initiated by _P. ostreatus_, which is the employed microorganism [34]. An additional reason justifying the increased protein profile concerns the secretion of various proteinaceous extracellular enzymes that display the ability to facilitate degradation during the procedure [35]. According to [PERSON] and [PERSON] [36], the elevated protein concentration could possibly be connected with the fungal growth and colonization of the employed microorganism [37]  
As has already been pointed out, CSC is a by-product with serious constraints and obstacles with respect to it being exploited as a feed supplement, especially for non-ruminants, all connected to gossypol's presence. This has initiated the implementation of various research endeavors toward the development of effective practices for the reduction of the contained FG and TG in order to be suitable for utilization in the animal sector. For this purpose, various strategies have been considered, among which the SSF presents an intriguing case, since it was determined as one of the most efficient. [PERSON] et al.