Supplementary Information (SI)
The role of electron donors generated from UV photolysis for accelerating
pyridine biodegradation
Yingxia Tang1, Yongming Zhang1, Ning Yan1, Rui Liu2, Bruce E. Rittmann3
1. Department of Environmental Science and Engineering, College of Life and Environmental Science,
Shanghai Normal University, Shanghai, 200234, P. R. China
R. China
2. Zhejiang Provincial Key Laboratory of Water Science and Technology, Department of Environmental
Technology and Ecology, Yangtze Delta Region Institute of Tsinghua University, Zhejiang, Jiaxing, 314006, P.
R. China
3. Swette Center for Environmental Biotechnology, Biodesign Institute, Arizona State University, Tempe,
AZ85287-5701, USA
Removal kinetics for the pyridine intermediate 2-hydropyridine (2HP)
The pyridine biodegradation pathway begins with transformation to 2-hydropyridine
(2HP), which then reacts further to downstream products (Figure 1 of the main manuscript):
Pyridine (C5H5N)  2-HP (C5H5ON)  downstream products
(S1)
The net accumulation of 2HP during pyridine biodegradation is given by:
C2HP = ΔCP – ΔC2HP
(S2)
where
C2HP is the concentration of 2HP (mM)
ΔCP is the cumulative concentration of lost pyridine (mM), which is equal to initial
pyridine concentration (CP0) minus the concentration of remaining pyridine (CP), or
ΔCP = CP0 – CP.
ΔC2HP is the cumulative concentration of 2-hydropyridine (mM) lost to downstream
products
Equation (S2) can be transformed by substitution of the definition of ∆CP:
C2HP = CP0 – CP – ΔC2HP
(S3)
which leads to
ΔC2HP = CP0 – CP – C2HP
(S4)
Here, CP0, CP and C2HP are, respectively, the initial pyridine concentration, the measured residual
pyridine concentration, and the measured 2HP concentration.
Figure 6 of the main text gives
the C2HP concentrations for experiments in which it was measured, along with the corresponding
CP concentrations.
Figure S1 presents the data for how ∆C2HP increase over time for the experiments of Figure
6.
The trends of the ∆C2HP data can be fit with:
C2HP 
C2HPmax t
K t
(S5)
Here, ∆C2HPmax is a maximum value of ∆C2HP, which should equal the initial pyridine
concentration; K is 2-hydropyridine loss coefficient; and t is elapsed time. In all cases,
∆C2HPmax equals 1.5 mM, or the maximum amount of transformed pyridine.
However, the K
values are lower for P+B and S+B (1.83 h) compared to B (3.99 h). This is evidence that the
biotransformation rate for 2HP was faster in the presence of succinate, whether added separately
or produced from photolysis.
Figure 7 of the main manuscript provides a more in-depth
analysis of the 2HP-biotransformation kinetics.
1.6
B(C)
B(E)
C (mM)
1.2
0.8
0.4
B: ΔC 2HPmax =1.5 (mM); K =3.99 (h); R2 =0.991
ΔC 2HP (mM)
0.0
1.2 0
4
8
T (h)
12
P+B(C)
0.8
0.4
16
P+B(E)
P+B: ΔC 2HPmax=1.5 (mM ); K =1.83 (h); R2=0.999
0.0
1.2
0
4
8
12
16
C (mM)
T (h)
S+B(C)
0.8
0.4
S+B(E)
S+B: ΔC 2HPmax=1.5 (mM ); K =1.83 (h); R2=0.999
0.0
0
4
8
t (h)
12
16
Figure S1. Cumulative loss of 2-hydropyridine (ΔC2HP) with time for the experiments in
Figure 6 of the main manuscript.
(E) symbols represent experimental values, and (C) lines
represent calculated values fit to Eqn. S5.