Electronic Supplementary Material
For
Removal of the Sesquiterpene βCaryophyllene from Air via Biofiltration:
Performance Assessment and Microbial
Community Structure
William M. Moe*, Weili Hu, Trent A. Key, Kimberly S. Bowman
Department of Civil and Environmental Engineering, 3515B Patrick Taylor Hall,
Louisiana State University, Baton Rouge, LA 70803, USA
*Corresponding author
Tel: (225) 578-9174
Email: [email protected]
1
Enrichment Culture Development
A sparged-gas bioreactor configuration similar to that reported previously for
development of enrichment cultures able to biodegrade a variety of volatile
organic compounds (Lee et al., 2002; Atoche and Moe, 2004; Moe and Qi, 2005;
Qi and Moe, 2006) was employed to develop an enrichment culture. The 4.0 L
glass kettle reactor (Pyrex, Acton, MA) was filled with 2.5 L of nutrient solution
containing the following constituents added to tap water: NH4NO3 1.25g/L,
KH2PO4 1.0 g/L, MgSO4·7H2O 0.5 g/L, CaCl2·2H2O 0.02 g/L, CuCl2·2H2O 0.17
mg/L, CoCl2·6H2O 0.24 mg/L, ZnSO4·7H2O 0.58 mg/L, MnSO4·H2O 1.01 mg/L,
Na2MoO4·2H2O 0.24 mg/L, NiCl2·6H2O 0.10 mg/L and FeSO4·7H2O 1.36 mg/L.
The reactor was inoculated with a 0.5 L suspension of commercially available
potting soil (Showscape Potting Soil, Phillips Bark, MS, USA) comprised of
ground and composted organic forest material, sand, and perlite. Air, at a flow
rate of 1.0 L/min, entered the reactor via a gas diffuser stone submerged in the
liquid medium. β-caryophyllene was delivered to the influent air supply by
manually injecting it into a glass, septum-filled injection port at repeated intervals
when it was visually observed that the previous injection had mostly evaporated
(approximately 3-day intervals).
On a daily basis, after adding DI water to reach a total volume of 3.0 L in the
reactor (to compensate for evaporative losses), 100 mL of the mixed liquid was
removed and 100 mL of nutrient solution was added while the reactor remained
mixed. This resulted in a hydraulic residence time (HRT) of 30 days. While there
was some growth in the aqueous phase (total suspended solids concentration
ranging from 19 mg/L to 72 mg/L over the duration of operation), a majority of
the biomass was present in the reactor as a fixed film growing attached to the
glass sidewalls and inner lid surface above the water level.
At the time of biofilter inoculation (182 days after startup of the sparged gas
reactor), biomass growing attached to the sidewall and inner lid surface of the
reactor (which had a surface temperature of 34°C) was scraped off and mixed
with 500 mL of reactor liquid. The resulting suspension was then homogenized in
a laboratory blender before use as inoculum for the laboratory biofilter.
2
Abiotic Adsorption Test
After the biofilter column was initially assembled but prior to microbial
inoculation, β-caryophyllene was supplied to the system to assess the abiotic
adsorption capacity of the polyurethane foam packing medium. The
experimentally measured breakthrough curve during β-caryophyllene loading to
the abiotic column (prior to inoculation) is depicted in Fig. S1. As shown, 5%
pollutant breakthrough occurred within one day, and 95% pollutant breakthrough
occurred after five days of continuous loading. Mass balance calculations revealed
that after complete breakthrough was achieved, the contaminant mass entering
and exiting the biofilter column differed by 0.939 g C. Assuming that all of the
pollutants measured as C were comprised of β-caryophyllene and using the
empirical formula for β-caryophyllene (0.882 g C / per g β-caryophyllene based
on the formula C15H24), the pollutant mass accumulating in the biofilter column
was calculated to be 1.06 g β-caryophyllene. The corresponding mass of βcaryophyllene adsorbed per unit mass of polyurethane foam was calculated to be
Effluent conce ntration (ppm C)
3.63 mg/g.
100
80
60
40
20
0
0
1
2
3
4
5
6
7
8
Tim e (days)
Fig. S1 Experimentally measured effluent concentration during the abiotic adsorption test
conducted prior to biofilter inoculation.
High Purity Versus Low Purity β-Caryophyllene
During the last five days of Period 1 (days 35-40), higher purity β-caryophyllene
(>98.5% purity as opposed to >90% purity) was supplied to the biofilter. Fig S2
depicts the influent and effluent concentrations for five days (days 30-35) low
purity β-caryophyllene (>90% purity) supplied to the biofilter following five days
higher purity β-caryophyllene (>98.5% purity) was applied. As shown in the
3
figure, the mean influent concentration for the higher purity β-caryophyllene
duration was 85.89±2.67 ppm C, it did not differ from the low purity βcaryophyllene duration of 83.7±4.0 ppm C. The effluent concentration was quite
stable through the ten days at the value of 3.3±0.2 ppm C.
Concentrations (ppm C)
100
80
Influent
Effluent
60
40
Low purity
ß-caryophyllene
20
High purity
ß-caryophyllene
0
30
32
34
36
38
40
Tim e (days)
Fig. S2 Influent and effluent concentrations from high purity β-caryophyllene experiment at the
end of Period 1.
On day 120, higher purity β-caryophyllene (>98.5% versus >90%) was supplied
to the biofilter for a duration of 4.85 days. Fig S3 depicts influent and effluent
pollutant concentrations during this short period of time. As it shown, the influent
concentration was 90.9±1.2 ppm C, essentially the same as the previous influent
concentration measurement, and the effluent concentration was 3.34±0.37 ppm C
which is quite similar to the effluent mean of 3.3±0.2 ppm C in Period 3B.
Concentration (ppm C)
140
Influent
Effluent
120
100
80
60
40
Low purity
ß-caryophyllene
High purity
ß-caryophyllene
20
0
115
117
119
121
123
125
Tim e (days)
Fig. S3 Influent and effluent concentrations measured during high purity β-caryophyllene test in
Period 3B.
4
Scanning Electron Microscopy
A representative scanning electron microscopy (SEM) image of packing medium
samples collected from the biofilter on day 145 are shown below in Fig. S4. A
large majority of the cells were rod-shaped (0.2 to 0.5 µm in width × 1 to 7 µm in
length) or cocci (0.2 to 1 µm diameter), consistent with the morphology of
bacteria. Some images revealed the presence of what appeared to be filamentous
fungi and higher organisms (e.g., nematodes); however, their relative abundance
was generally low.
Fig. S4 SEM image of biofilter packing medium sampled from the inlet section of the biofilter on
day 145. Bar represents 1.0 µm.
5
Physicochemical Properties of -caryophyllene
Because experimental data are not available regarding several physicochemical
properties of -caryophyllene, estimation methods were applied using models
freely available in the EPI SuiteTM version 4.10 software package (US EPA, 2011,
http://www.epa.gov/oppt/exposure/pubs/episuitedl.htm). This approach has been
utilized previously to estimate properties of other sesquiterpenes (Jenner et al.,
2011). Tabulated results are provided in Table S1.
Table S1: Physicochemical properties of -caryophyllene
a
Parameter
Value
Molecular Formula
C15H24
CAS #
87-44-5
Molecular Weight (g/mole)
204.36
Density at 20ºC (g/mL)
0.902
Boiling point (°C)
262-264
Log KOW (dimensionless)
6.30a
Water Solubility at 25°C (mg/L)
0.05 b -0.54 c
Henry’s Law Constant at 25°C (atm·m3/mol)
0.69d
(unitless)
28.2d
Vapor Pressure (Pa at 25 °C)
4.16e
KOW=octanol-water partition coefficient, estimated using WSKOWWin version 1.67,
atom/fragment contribution method.
b
Water solubility estimated using WSKOWWin version 1.41 regression equation.
c
Water solubility estimated using WATERNT version 1.01.
d
Henry’s Law constant estimated using the Bond contribution method in HenryWin version 3.20.
e
Vapor pressure estimated as the mean of the Antoine and Modified Grain Method in MPBPWin
version 1.43.
The estimated vapor pressure for -caryophyllene shown in Table S1 is somewhat
higher than the value of 1.1 Pa estimated using the alternative approach of
Hoskovec et al. (2005).
6
References Cited
Atoche JC, Moe WM (2004) Treatment of MEK and toluene mixtures in biofilters: Effect of
operating strategy on performance during transient loading. Biotechnol Bioeng 86:468-481. doi:
10.1002/bit.20064
Hoskovec M, Grygarova D, Cvačka J, Streinz L, Zima J, Verevkin SP, Koutek B (2005)
Determining the vapour pressures of plant volatiles from gas chromatographic retention data. J
Chromatography A 1083:161-172. doi: 10.1016/j.chroma.2005.06.006
Jenner KJ, Kreutzer G, Racine P (2011) Persistency assessment and aerobic biodegradation of
selected cyclic sesquiterpenes present in essential oils. Environ Toxicol Chem 30:1096-1108. doi:
10.1002/etc.492
Lee S, Moe WM, Valsaraj KT, Pardue JH (2002) Effect of sorption and desorption-resistance on
aerobic trichloroethylene biodegradation in soils. Environ Toxicol Chem 21(8):1609–1617. doi:
10.1897/1551-5028(2002)021<1609:EOSADR>2.0.CO;2
Moe WM, Qi B (2005) Biofilter treatment of volatile organic compound emissions from
reformulated paint: Complex mixtures, intermittent operation, and startup. J Air Waste Manag
Assoc 55:950-960. doi: 10.1080/10473289.2005.10464687
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