Bacterial growth yields on EDTA, NTA, and their biodegradation intermediates

Abstract

Ethylenediaminetetraacetic acid (EDTA) and nitrilotriacetic acid (NTA) are widely used anthropogenic chelating agents for control of metal speciation and are ubiquitous in natural waters and wastewaters. This is the first report of systematic measurement of the growth yields of a mixed culture (BNC1-BNC2) on EDTA and its biodegradation intermediates, and of Aminobacter aminovorans (aka Chelatobacter heintzii) ATCC 29600 on NTA and its biodegradation intermediates. The yields measured for BNC1-BNC2 co-culture were 75.0 g of cell dry weight (CDW) (mole of EDTA)(-1), 68.6 g of CDW (mole of ED3 A)(-1), 51.2 g of CDW (mole of N,N'-EDDA)(-1), 34.5 g of CDW (mole of ED)(-1), 26.3 g of CDW (mole of IDA)(-1), 12.2 g of CDW (mole of glycine)(-1), and 9.7 g of CDW (mole of glyoxylate)(-1). The yields measured for A. aminovorans were 44.3 g of CDW (mole of NTA)(-1), 37.9 g of CDW (mole of IDA)(-1), 15.2 g of CDW (mole of glycine)(-1), and 10.4 g of CDW (mole of glyoxylate)(-1). The biodegradation pathways of EDTA, NTA, and several of their metabolic intermediates include reactions catalyzed by oxygenase enzymes, which may reduce energy available for cell synthesis. Comparison of measured yields with predicted yields indicates that the effect of oxygenase reaction on cell yield can be quantified experimentally as well as modeled based on thermodynamics.