Integrated Bioprocessing of Phytoremediation-Derived Chlorella Biomass: Enzymatic Activity Profiles During Saccharification and Fermentation with Wickerhamomyces sp.

Abstract

Residual microalgal biomass generated during wastewater phytoremediation represents an underexploited resource for developing sustainable bioprocesses. This study investigated the biotechnological valorization of phytoremediation-derived Chlorella biomass through an integrated process combining α-amylase-assisted saccharification and fermentation with the non-conventional yeast Wickerhamomyces sp. UFFS-CE-3.1.2 in a stirred-tank bioreactor. Following physical pretreatment to enhance intracellular compound accessibility, fermentation was conducted for 72 h under anaerobic conditions, and temporal changes in enzymatic activities and fermentation-associated compounds were monitored by spectrophotometric assays and high-performance liquid chromatography (HPLC), respectively. The integrated process exhibited distinct temporal profiles of hydrolytic and antioxidant enzyme activities, with maximum activities of 1275.23 U/mL for catalase, 1014.59 U/mL for ascorbate peroxidase, 1291.67 U/mL for protease, and 228.75 U/mL for lipase. Amylase activity remained detectable throughout the 72 h process. Total sugars decreased from 8.88 g/L at 0 h to 0.03 g/L at 72 h. In comparison, glycerol peaked at 5.62 g/L at 18 h, and ethanol remained at approximately 1.0 g/L between 18 and 48 h. Because several enzymatic activities were already detected before yeast inoculation, the observed profiles cannot be attributed exclusively to Wickerhamomyces sp. and should instead be interpreted as characteristics of the integrated bioprocess. Overall, the results demonstrate that residual Chlorella biomass generated during wastewater phytoremediation can serve as a renewable feedstock for further biotechnological processing, supporting an extended valorization pathway within a circular bioprocessing framework.