Valorization of grape pomace and orange peels: Improved production of hydrolytic enzymes for the clarification of orange juice

The production in solid state fermentation (SSF) of several hydrolytic enzymes by Aspergillus awamori on a mixture of grape pomace and orange peels has been studied in two configurations of bioreactor: packed bed and tray-type. When the effect of aeration in both reactors was compared, using the trays-type with an air flow rate of 3 mL/gds·min, average activities of 42.64 and 2.16 IU/gds were measured for xylanase and CMCase, respectively; however in the case of the column reactor the aeration must be doubled to obtain similar activity values. These differences were more significant in the case of exo-PG. The extracts obtained in this reactor were applied to orange juice and the cloudiness was markedly reduced, even improving the efficiency of a commercial enzyme preparation. Thus, while the turbidity of the fresh juice was 4625 NTU, treatment with the extracts reduced the value to 24.25 NTU. In a similar way the clarity increased to 95% after treatment with enzyme extracts. According to the results obtained, the proposed process for grape pomace and orange peels reutilization constitutes a viable alternative for many companies to revalorize their residues and to reduce their contaminant capacity.

► Two agro-industrial residues have been valorized for the production of enzymes. ► Aeration improved the production of exo-polygalacturonase, xylanase and CMC-ase. ► Trays reactor is better than column reactor for obtaining high enzymes productivities. ► Enzyme extracts obtained can be successfully applied for orange juice clarification.