Use of citric pulp in cultivation of Aspergillus niger and Trichoderma reesei for cellulases and polygalacturonase production by bioprocess with cell recycle

The production of biofuels and food from clean technologies and renewable sources are a global concern. In this context great importance is being given to the use of agro-industrial waste. The citrus pulp obtained from orange (Citrus sinensis) in industrial process is an important residue that only in São Paulo - Brazil is estimated at 7.7 x10⁶ tons/year. Enzyme production from this waste can reduce costs of biotechnological processes for the production of food and bioenergy since this residue is not expensive. In this study it was evaluated citrus pulp as substrate for the production of polygalacturonases and cellulases by Trichoderma reesei or Aspergillus niger in a batch process of fermentation with cell recycle.  The residue from this fermentation was evaluated for crude protein. The citrus pulp proved to be an efficient substrate for the production of polygalacturonases reaching 8.05 U/mL of Aspergillus niger culture in 72 h after cell recycle. The production of cellulases occurred for both A. niger and Trichoderma reesei , with peaks of 0.57 and 0.72 FPU/mL respectively. As for protein enrichment of the filtered biomass after cultivation with cell recycle  using A. niger and T. reesei, there was a great increase from original citrus pulp (7.97%) to the final residue, 22.8% and 26.8 % respectively. Therefore, with this process it is possible the production of cellulases for 2^nd generation bioethanol and polygalacturonases and protein for food applications. The proposed bioprocess is promising and deserves a more thorough economic study.