Method for monitoring the fate of green fluorescent protein added to aerobic and anaerobic wastewater sludge

The fate of active proteins in environmental matrices such as wastewater sludge, soil, and organic amendments is not well understood . In the present paper, we report the use of green fluorescent protein (GFP) as a probe protein to investigate the behaviour of proteins in wastewater sludge. We developed a procedure to quantitatively detect the active form of this protein in such a matrix. The procedure is based on the fluorimetric analysis of GFP in the separated liquid and solid fractions of sludge. We then tested the suitability of the approach by monitoring GFP added to aerobic and anaerobic sludge. Under aerobic conditions at 20 °C, most GFP immediately associated with the sludge solid fraction. About 20% of the fluorescence due to solid fraction associated GFP was still present after 72 h, which suggests a relative persistence of proteins in this system. Under anaerobic conditions at 35 °C, fluorescence signal due to GFP was reduced by 90% after only 6 h.