## 4 Discussion
Among the fungi, _Aspergillus_ and _Scopulariopsis_ had the highest number of strains and were isolated at different sampling times. The most frequent fungi isolated under semipermeable film were _Aspergillus_, _Circinella_ (saprotrophic and nematophages fungi), and _Talaromyces_. They have been described as fungi responsible for organic matter degradation in the thermophilic phase due to their resistance to high temperatures (50-65 \({}^{\circ}\)C). These filamentous fungi belong to Hypocreales, Sordariales, and Microascales or orders with high representation in the mesophilic and thermophilic phases. A similar dynamic was described by [PERSON] et al. [28], where members of _Aspergillus_, _Scopulariopsis_, and _Acemonium_, characterised this process. In this study, _Aspergillus versicolor_ HM30 was isolated at the beginning of the process, a common inhabitant in all the environments. Previous studies have reported xylanase production by this species and its potential to bioaccumulate heavy metals and degrade dyes in water effluents [29; 30]. All of these fungi, except _Scopulariopsis_, _Coprinopsis_ (_Hornographiella_), and _Trichosporon_, have been identified in composting processes using pyrosequencing techniques [31]. However, _S. brevicaulis_ has been isolated in the composting of lignocellulosic material, in the mesophilic and thermophilic phases [9]. This species has been recently described as degrader of polycyclic aromatic hydrocarbons (PAHs) like anthracene and described as a thermotolerant fungus [32; 33]. In this pile, fungi such as _Hornographiela aspergilatta_ and _Emericella nidulans_ have not been previously described in the sewage sludge composting process and they showed a high number of enzymes. _Hornographiela aspergilatta_, an opportunist pathogen related to complications in patients undergoing treatments for lung diseases [34], could not be considered as a GRAS microorganism (Generally Recognised as Safe). However, its enzymes could be used from previous extraction or genetic engineering. As well, _Emericella nidulans_ HM22 produced all the enzymes studied. The ability of this species to produce enzymes involved in cellulose degradation, like xylanase, has been reported previously [35]. This species has been isolated from soil and is considered a thermotolerant fungus, and could be regarded as a species with a potential biotechnological application and a good candidate for further studies. It is interesting to note the presence in the maturation stage of _Thielavia_ and _Bjerkandera_ sp. _Thielavia_ sp. HM70 showed positive results for nine enzymes, four of them corresponding to lignocellulosic enzymes. _Thielavia_ is an ascomycete fungus that includes mesophilic and thermophilic species able to secrete up to five types of laccases [36; 37]. _Bjerkandera_ sp. HM70 was also identified in the maturation stage. This fungus is a white rot fungus, whose whole genome has been sequenced and it is characterised by the presence of a broad set of enzymatic activities, mainly peroxididases such as versatile peroxidase, manganese peroxidase, and inducible lacases in the presence of lignocellulosic material [38]. Concerning bacteria, _E. ficeum_ (strains BM08 and BT08) showed a remarkable activity. This bacteria has been widely isolated from water and soil samples and has been reported as an efficient degrader of aromatic compounds [39]. _Bacillus_ was identified in several strains during the process. _B. pumilus_, BM02, BM05, and BT02 had a higher number of activities like proteolytic, amyloidytic, pectinolytic, hemicellulose, peroxidase, and polyphenol oxidase. These results are in accordance with previous studies in which _B. licheniformis_ and _B. pumilus_ were described as polyphenol oxidase and peroxidase producers [40]. These strains showed a broad metabolic profile and have been previously characterised by their ability to produce peroxididases and proteases.