Immobilization of a novel formaldehyde-degrading fungus in polyvinyl alcohol–sodium alginate beads for continuous wastewater treatment

Abstract

This study introduces a novel formaldehyde-degrading fungus, identified as Geotrichum sp. YC8 based on microscopic morphology and internal transcribed spacer gene sequence analysis. The strain can efficiently degrade 100 mg/L formaldehyde even under high-salinity conditions (50 g/L NaCl) or at an acidic pH of 2.0. Optimal degradation conditions, determined via response surface methodology, were 31.4 °C, pH 5, and 12 % inoculum. YC8 cells were encapsulated in a polyvinyl alcohol–sodium alginate hydrogel to enhance biodegradation, with an optimal formulation of 2 % sodium alginate, 6 % polyvinyl alcohol, and 3 % calcium chloride. The impact of hydrogel bead size on mass transfer efficiency was also evaluated. Batch tests revealed that immobilized cells were more resilient, achieving complete degradation of 800 mg/L formaldehyde within 55 h. Both free and immobilized cells exhibited first-order kinetics at low concentrations and zero-order kinetics at high concentrations. The immobilized cells maintained stable performance in a fluidized bed reactor, enabling continuous degradation of 900 mg/L formaldehyde. This study highlights YC8 as a promising agent for practical formaldehyde degradation applications.