Effects of enzymatic treatment on the reduction of extracellular polymeric substances (EPS) from biofouled membranes

ABSTRACT

Biofouling is a major problem in a membrane-based water treatment systems because it causes a water flux decline and necessitates an increase in cleaning frequency. The objective of this study was to evaluate the effectiveness of an enzyme treatment method on the reduction of extracellular polymeric substances (EPS). For this enzyme treatment test, acylase I was used as it cleaves quorum sensing signal molecules and proteinase K degrading proteins. It was found that 5 μg/mL of acylase I, 100 μg/mL of proteinase K, and a combination of both enzymes (5 μg/mL of acylase I and 100 μg/mL of proteinase K) could remove 9.0, 56.6, and 33.7% of the bacteria on an reverse osmosis membrane, respectively. Proteinase K removed 33.6% of the EPS concentration per cell number. Although acylase I reduced bacteria numbers at high removal efficiency, it could not remove EPS—and, indeed, increased the number of cells (6.2 × 10⁻³μg-EPS/cells) compared with the control sample (5.2 × 10⁻³μg-EPS/cells). From the excitation emission matrix result, the peak intensities of UV, marine, and visible humic-like substances were decreased after enzyme treatment, but the amount of protein-like substances were not affected. For a more effective biofouling reduction, the enzyme treatment method should thus be accompanied by another EPS-degrading agent.

Keywords:

• Biofouling
• Pseudomonas aeruginosa
• Acylase I
• Proteinase K
• Extracellular polymeric substances

Acknowledgements

This research was supported by a grant (07SeaHeroA01-01) from the Plant Technology Advancement Program funded by the Ministry of Land, Transport and Maritime Affairs, Korea. The authors would also like to thank Prof. Cho’s lab in the Gwangju Institute of Science and Technology for the use of their TOC analyzer.

Notes

Presented at The Fifth Desalination Workshop (IDW 2012), October 28–31, 2012, Jeju, Korea

*N.A.: Not Available.