Integrated Extractive Fermentation and Aqueous Two-Phase Systems Enable Efficient Production and Purification of an Extracellular Protease from Aspergillus sp. UCP1287

Proteases are among the most commercially important industrial enzymes, yet their large-scale production is often limited by complex and costly downstream processing. In this study, an integrated bioprocess was developed for the production, in situ recovery, and purification of an extracellular protease produced by Aspergillus sp. (SIS 22/UCP 1287) under submerged fermentation. Enzyme extraction was coupled directly to fermentation using a polyethylene glycol (PEG)–phosphate aqueous two-phase system (ATPS), aiming to enhance recovery while preserving enzymatic activity. The effects of PEG molecular weight, polymer and phosphate concentrations, and pH on enzyme partitioning were systematically investigated through a full factorial experimental design. Low-molecular-weight PEG and near-neutral pH conditions significantly favored enzyme migration to the PEG-rich phase. Under optimized conditions (15% PEG 3500, 20% phosphate, pH 7.0), the ATPS achieved a partition coefficient of 65.55, enzyme recovery of 209%, and a purification factor of 1.64. Subsequent purification by DEAE–Sephadex ion-exchange chromatography yielded a tenfold increase in specific activity, with optimal elution at 0.5 M NaCl. SDS–PAGE analysis confirmed the homogeneity of the purified protease, revealing a single band at approximately 59 kDa. Overall, the proposed integrated ATPS–chromatography strategy represents a robust, scalable, and environmentally friendly platform that significantly simplifies downstream processing while maintaining high enzyme activity, highlighting its potential for industrial and biotechnological applications.