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Filamentous fungi are known for their significant potential in biotechnology, thanks to their versatile enzyme systems with various applications. However, dealing with their growth patterns and structural configurations presents significant challenges. To tackle these issues, fungal pellets are emerging as potential solutions, providing compact biomass aggregates that offer distinct advantages for bioprocesses. This study delves into characterization and optimizing pellet formation for Pleurotus ostreatus and Rhizopus stolonifer using the Taguchi methodology, aiming to enhance their biotechnological applications. By systematically varying parameters such as agitation level (AL), glucose concentration (GC), and inoculum size (IS), we identified key factors influencing pellet formation. Results indicate that P. ostreatus forms pellets in rich media from mycelium, while R. stolonifer requires a minimal medium with pH modifications for pelletization via a coagulative mechanism. The optimization process reveals that agitation level is a crucial factor for maximizing pellet production in both models, while the other factors do not seem to influence the process significantly but impact the morphology and quantity of pellets. The results suggest that by optimizing parameters using the Taguchi method, it is possible to achieve acceptable pellet formation performance in both fungi. Understanding these factors is essential for improving the efficiency of biotechnological processes involving fungal biomass, providing valuable insights into enhancing fungal pellet production for various applications.

The fungal cell wall is an attractive structure to look for new antifungal drug targets and for understanding the host-fungus interaction. Sporothrix schenckii is one of the main causative agents of both human and animal sporotrichosis and currently is the species most studied of the Sporothrix genus. The cell wall of this organism has been previously analyzed, and rhamnoconjugates are signature molecules found on the surface of both mycelia and yeast-like cells. Similar to other reactions where sugars are covalently linked to other sugars, lipids, or proteins, the rhamnosylation process in this organism is expected to involve glycosyltransferases with the ability to transfer rhamnose from a sugar donor to the acceptor molecule, i.e., rhamnosyltransferases. However, no obvious rhamnosyltransferase has thus far been identified within the S. schenckii proteome or genome. Here, using a Hidden Markov Model profile strategy, we found within the S. schenckii genome five putative genes encoding for rhamnosyltransferases. Expression analyses indicated that only two of them, named RHT1 and RHT2, were significantly expressed in yeast-like cells and during interaction with the host. These two genes were heterologously expressed in Escherichia coli, and the purified recombinant proteins showed rhamnosyltransferase activity, dependent on the presence of UDP-rhamnose as a sugar donor. To the best of our knowledge, this is the first report about rhamnosyltransferases in S. schenckii.