Lipase-rich fermented solids produced by wickerhamiella osmotolerans: direct application as biocatalysts for dairy wastewater treatment and integration with coagulation/flocculation/sedimentation

Lipase-based bioprocesses are promising alternatives for the treatment of lipid-rich industrial effluents; however, enzyme recovery and purification steps may limit their practical application. In this study, lipase-rich fermented solids produced by Wickerhamiella osmotolerans under solid-state fermentation were evaluated as direct biocatalysts for dairy wastewater treatment. A total of 39 yeast isolates obtained from poultry slaughterhouse wastewater were screened for lipolytic activity. Five isolates with the highest enzymatic indices were selected for molecular identification and identified as Wickerhamiella osmotolerans based on sequencing of the D1/D2 region of the 26 S rDNA. Lipase production was evaluated through sequential experiments investigating particle size, substrate/support composition, moisture content, fermentation time, and inducer addition. Although 100% sunflower seed produced the highest lipolytic activity, the sunflower seed/rice husk mixture (1:1) was selected as a practical trade-off between enzyme production and the incorporation of an agro-industrial residue. Under the selected conditions of 60% initial moisture and 24 h of fermentation, this mixture reached 24.14 U g⁻¹ without external lipid inducers. The direct application of the fermented solid resulted in 65.4% apparent O&G removal but did not reduce turbidity. The subsequent C/F/S step reduced turbidity from 1190 to 693 NTU, corresponding to a stage-specific reduction of 41.8%, but did not provide additional O&G removal. These findings demonstrate a proof-of-concept strategy for simplifying lipase application by eliminating enzyme extraction steps and integrating microbial enzyme production with wastewater treatment.