Penicillium citrinum whole-cells catalyst for the treatment of lipid-rich wastewater

Highlights: • Whole cells of Penicillium citrinum hydrolyzed lipids in dairy wastewater. • Free whole cells had higher hydrolysis efficiency than immobilized whole cells. • Methane production was highest with simultaneous enzymatic and biological treatment. -- Abstract: The performance of Penicillium citrinum whole cells in decreasing lipid and organic contents in dairy wastewater was investigated using sequential and simultaneous treatment processes (enzymatic hydrolysis and anaerobic digestion). Free and immobilized whole cells were used as catalysts for the treatment of dairy wastewater at pH 4.0, 7.0, and 8.0 (optimal pH for P. citrinum whole cell activity) for 48 h. Percent hydrolysis was higher at pH 8.0. Free whole cells achieved a 1.3-fold higher percent hydrolysis (92.5%) than immobilized whole cells. Biodegradability tests were conducted using crude wastewater (E1), wastewater prehydrolyzed by whole cells (E2), and wastewater simultaneously submitted to whole-cell hydrolysis and biodigestion (E3). Low removal of organic matter was obtained in all tests (mean of 43%). E2 and E3 resulted in higher methane production rate than E1, which demonstrates the benefits of combining enzymatic hydrolysis and anaerobic digestion for wastewater treatment, whether sequentially or simultaneously.