Enzymatic Transformation and Bonding of Sulfonamide Antibiotics to Model Humic Substances

Table 3

Concentrations of sulfonamides and hydroxyphenol derivate reacted in the absence or presence of laccase, and resulting rate coefficients of the dissipation of sulfapyridine (SPY), sulfadimethoxine (SDT), and sulfanilamide (SAA).

sulfonamide	sulf. (mmol L^−1)	phenol (mol L^−1)	Laccase (U mL^−1)	Kinetic model	(h^−1)		SE
SPY	0.075	0	0	Zero order (1)	0.003	0.439	0.008
	0.075	0.007	0		0.047	0.910	0.035
	0.075	0.013	0		0.093	0.996	0.060
	0.075	0.020	0		0.140	0.950	0.089
	0.075	0.027	0		0.144	0.981	0.125
	0.075	0.033	0		0.156	0.998	0.144
SDT	0.075	0.033	0		0.131^a
SAA	0.075	0.033	0		0.003^a
SPY^b	1.00	0	48	First order (2)	0.113	0.995	0.033
SDT^b	1.00	0	48		4.29 10^−3	0.882	0.125
SAA^b	1.00	0	48		2.99 10^−4	0.990	0.034
SPY	1.00	0.050	2	First order (2)	0.517	0.966	0.032
SDT	1.00	0.050	2		0.490	0.971	0.060
SAA	1.00	0.050	2		0.447	0.982	0.037

Degradation of SAA and SDT was measured only at one timepoint (5 d). It was assumed that degradation followed zero order kinetics as it was determined for SPY.
^bData from [20].