Optimization of Decolorization of Palm Oil Mill Effluent (POME) by Growing Cultures of Aspergillus Fumigatus Using Response Surface Methodology

8/18/2019 Optimization of Decolorization of Palm Oil Mill Effluent (POME) by Growing Cultures of Aspergillus Fumigatus Using…

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oil mill industry in Malaysia has been identified as the

largest contributor to the pollution load in rivers throughout

the country. The effluent is colored due to the presence of

lignin and its degraded products, tannin, and humic acids

from crushed palm nut and also lipids and fatty acids re-

leased during steam extraction process (Oswal et al. 2002).

Discharge of colored effluents imparts color to receiving

waters and thus inhibits the growth of marine organisms by reducing the penetration of sunlight, with a consequent

reduction in photosynthetic activity. The colored com-

pounds may chelate with metal ions and thus become di-

rectly toxic to aquatic biota (Mohan and Karthikeyan 1997).

Besides, the humic substances will react with chlorine in

drinking water treatment and produces carcinogenic by-

products such as trihalomethanes (Vukovic et al. 2008). In

addition, substances derived from lignin in POME can pos-

sibly inhibit embryonic development in marine organisms

(Pillai et al. 1997). There is great concern from the public on

the environmental effect of colored wastewater as compared

to harmful wastewater that is colorless (Gupta et al. 2006b).Therefore, it is necessary that the color present in the efflu-

ent is removed before discharge into receiving water bodies.

The existing POME treatment technology such as pond-

ing systems (combination of anaerobic and aerobic pond

processes) is inefficient for the removal of its dark brown

color. It should be highlighted that the POME is treated

without adding any chemicals or biological agents and is

dependent solely on the existence of indigenous microor-

ganisms. Since color has recently emerged as a critical water

quality parameter under the Malaysian Environmental Qual-

ity Act 2009, the removal of colored compounds from

POME has become an important problem to be addressed.

Various studies such as membrane technology (Raja Ehsan

Shah and Kaka Singh 2004; Sulaiman and Ling 2004) and

activated sludge – granular-activated carbon (Zahrim et al.

2009) have been used to achieve the present discharge limit;

nevertheless, color removal in POME remains a major prob-

lem. Besides the inefficient removal of color, the application

of membrane technology also suffers from fouling due to

high suspended solids in POME, while granular-activated

carbon is costly and not economically feasible for industrial

application. Electrocoagulation caused the reduction of the

brown, opaque effluent of raw POME to a pale yellow

solution. Although effective in color removal, there is a

major operational issue in electrocoagulation (Agustin et

al. 2008). Electrode passivation (blockage of the surface of

the electrode) results in a drastic increase in maintenance

costs (Holt et al. 1999). A recent study conducted using

aerobic granular sludge in sequencing batch reactor for color

removal averaged at only 38 % removal with an initial

ADMI of 600 (Abdullah et al. 2011).

Adsorption is a promising technique for the removal of

impurities and color and has potential application for the

treatment of real industrial wastewater. There are two types

of adsorption: One involving nonbiomass material such as

macrocomposite (Lim et al. 2011), bottom ash, and deoiled

soya for the removal of dye (Gupta et al. 2006a ) and remov-

al of dye (Gupta et al. 2007a ), fluoride (Gupta et al. 2007b),

and hexavalent chromium (VI) (Gupta et al. 2010) by car-

bon slurry. The other type of adsorption involves the use of

biomass, either living or nonliving biomass, which is alsoknown as biosorption. Biosorption using biomass has been

found to be convenient, versatile, and economical for impu-

rities removal and offer an alternative technology for the

removal of color in POME. Research on biomass adsorption

has been mostly used for the removal of heavy metal by

nonliving biomass such as cyanobacterium for the removal

of chromium (Gupta and Rastogi 2008d) and green algae for

the removal of hexavalent chromium (Gupta and Rastogi

2009; Gupta et al. 2001), lead (Gupta and Rastogi 2008a ),

and copper (Gupta et al. 2006c). In addition, biosorption of

dye using nonliving biomass such as wheat husk (Gupta et

al. 2007c) has been also reported. Living biomass such asgrowing fungal cells have also been used for the removal of

the dye Acid Brilliant Red B (Xin et al. 2012) as well as

cadmium and zinc (Liu et al. 2006). The use of growing

cells for biosorption of color leads to simpler nutrient re-

quirement since POME can provide suitable buffering sys-

tem and nutrients for the growth of fungi. In addition, the

system is simple and economical. Up till now, most of the

studies found in the literature focused on the biosorption of

color using dead cells of fungi (Patel and Suresh 2008; Aksu

and KarabayIr 2008). However, in this study, fungi were

grown in POME. The subsequent increase in biomass in-

creased the adsorption of color and the removal of other

compounds in POME. This can further enhance the efficien-

cy of the treatment process for the removal of chemical

oxygen demand (COD), total polyphenolic compounds, lig-

nin content, and ammoniacal nitrogen content. Decoloriza-

tion of colored wastewater such as pulp and paper

wastewater, molasses wastewater, and olive mill effluent

using fungi had been reported in the literature. To the best

of our knowledge, decolorization of POME using fungi has

yet to be reported.

The application of response surface methodology (RSM)

has been previously reported for the optimization of distill-

ery wastewater decolorization using growing cells of Asper-

gillus fumigatus (Mohammad et al. 2006), decolorization of

dye using growing cells of Pseudomonas sp. (Du et al.

2010), laccase (Murugesan et al. 2007), and NaOH-

modified rice husk (Chowdhury et al. 2012), and removal

of lignin in pulp mill wastewater (Wang et al. 2011). These

show the extensive and diverse applications of RSM, par-

ticularly in situations where various factors could affect the

efficiency of the process. Hence, this study aimed at opti-

mizing the decolorization of POME by locally isolated A.

Environ Sci Pollut Res (2013) 20:2912 – 2923 2913


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fumigatus using RSM. The effects of the types and concen-

trations of carbon and nitrogen sources, pH, temperature,

and size of the inoculum to the decolorization activity were

identified.

Materials and methods

POME sampling and preparation

Treated POME, or better known as final POME, was

obtained from a local oil palm mill and stored at 4 °C. It

was autoclaved at 121 °C for 15 min to eliminate the

indigenous microbes. The autoclaved POME was then

centrifuged at 4,000 rpm for 15 min to eliminate suspended

solid materials. The POME was used in subsequent experi-

ments (without filtration and dilution).

Fungal isolation, cultivation, and identification

Locally isolated fungi were obtained from diverse environ-

mental samples such as POME, POME sludge, textile

sludge, soil, wood, grass, spoilt food, and pineapple wastes.

Samples were aseptically placed onto potato dextrose agar

containing 10 % v / v sterilized POME. Different fungal

strains were isolated into a single colony by repeated sub-

culturings. A total of 24 fungal strains were maintained at

4 °C on agar plate and were screened for their decolorization

potential. A small piece of agar block was cut out from the

agar plate of actively growing fungi and transferred into

POME (pH was adjusted to pH 5 using HCl). It was cultured

at ambient temperature (26 – 28 °C) under shaking condition

(150 rpm) supplemented with glucose (1 % w/ v ) and pep-

tone (0.5 % w/ v ). Fungi that showed high decolorization

capability were further used for the study. For the prepara-

tion of the inoculum, the fungal strain that showed the best

decolorization was grown on agar plate and the spore was

harvested to make a spore suspension with 106/mL spore

number as described by Chidi et al. (2008).

Total DNA was extracted from fungal spores using the

Norgen DNA Isolation Kit. For the polymerase chain reac-

tions (PCR), the primers ITS1 (5′ TCC GTA GGT GAA CCT

TGC GG 3′) and ITS4 (5′ TCC TCC GCT TAT TGA TAT GC

3′) were used to amplify the 18S rDNA fragment sequence.

PCR conditions were prepared as described by Korabecna

(2007) using the Bio-Rad MJ Mini Personal Thermal Cycler.

The aligned sequences were analyzed using the Basic Local

Alignment Search Tool (BLASTn) online analysis tool.

Optimization experimental design and data analysis

The first step in optimization was to identify supplementa-

tion of various sources of carbon and nitrogen into POME to

enhance the decolorization efficiency of the isolated A.

fumigatus. A general factorial design (Stat Ease, Design

Expert software 6.0.4) is useful in the optimization of cate-

gorical factors and is able to identify the interaction of

carbon and nitrogen in influencing the decolorization pro-

cess. Selected carbon sources such as glucose, sucrose,

fructose, carboxymethyl cellulose (CMC), and glycerol at

a concentration of 1 % w/ v and nitrogen sources such asyeast extract, peptone, urea, and ammonium sulfate at a

concentration of 0.5 % w/ v were utilized in a series of

experiments. POME (pH 5) were inoculated with 10 % v / v

spores (106/mL) and incubated at ambient temperature for

the maximum predetermined time period of 5 days. A total

of 90 experimental runs were carried out and the average of

triplicate experiments of decolorization percentages was

recorded.

Glucose was chosen as the best carbon source and was

further optimized using a two-level factorial design together

with other numerical factors. Two-level factorial design was

used as a screening tool to determine important factorsaffecting decolorization. The four independent variables that

may affect decolorization were coded at three levels be-

tween −1 and +1 for which the actual range is shown in

Table 1. A triplicate full-factorial design (total experimental

run is 48) was selected with 8 center points. All experiments

were set at different conditions as the experimental run and

incubated for 5 days at 150 rpm.

The central composite design (CCD) was used to find the

optimum response within the specified range of the factors.

It is built from the two-level factorial design with center

points and axial points which are able to provide more

precise results compared to the two-level factorial design.

Three independent variables, namely, pH, glucose concen-

tration, and temperature, were included in face-centered

CCD (Table 2), while insignificant parameters (inoculum

size) from the result of the two-level factorial design were

kept at a minimum level throughout the studies. The actual

range of the independent variables is shown in Table 1. The

experiment was conducted in triplicates (total experimental

run is 42) with 6 center points. A final experiment was

conducted to validate the CCD model developed.

Table 1 Coded and uncoded values of the experimental variables for

two-level factorial design

Independent variables Symbols Coded level

−1 (low level) 0 +1 (high level)

pH A 4 5 6

Glucose concentration

(% w/ v )

B 0.5 1.0 1.5

Temperature (°C) C 30 35 40

Inoculum size (% v / v ) D 2.5 7.5 12.5

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Analytical methods

To separate the fungal biomass and the liquid medium, the

whole fungi culture was centrifuged at 4,000 rpm for 15 min

at 4 °C. The color (ADMI unit), COD (reactor digestion

method), and ammoniacal nitrogen (Nessler method) were

determined according to the HACH Method (2005) by

HACH DR 5000. The pH was measured using the Sartorius

PB-10 pH meter. Total polyphenolic compounds were quan-tified using a reaction with the Folin – Ciocalteu reagent

(Singleton et al. 1999). The total amount of polyphenolic

compound that remained in the culture medium was deter-

mined using gallic acid as standard. The lignin content of

the effluent was estimated using kraft lignin as standard

(Pearl and Benson 1990). All experiments were conducted

in triplicates.

Biodegradation and biosorption study

Fungal culture grown in POME was centrifuged at

4,000 rpm, 4 °C for 15 min. The supernatant was discarded

and the pellet was mixed with an equal volume of NaOH

(0.1 M) solution. The sample was centrifuged at 4,000 rpm,

4 °C for 15 min (Patel and Suresh 2008). The remaining

color in the supernatant was measured as described in the

“Analytical methods” section.

After 5 days of decolorization in POME and desorption

using 0.1 M NaOH, the mycelia of the A. fumigatus were

collected, washed several times with sterile distilled water,

and dried for 24 h at 70 °C. The samples were gold-coated

using the Bio-Rad Polaron Division SEM Coating System.

Fourier transform infrared (FTIR) spectroscopy (Nicolet

iS5) was used to identify the functional groups present in the

samples. The sample/KBr mass ratio used for the prepara-

tion of the disks was 1:200 within the IR region of the

frequency 400 – 4,000 cm−1 at a scan speed of 16 cm/s.

Besides fungus after 5 days decolorization and desorption,

A. fumigatus was also cultured in mineral salts medium

(0.1 % w/ v KH2PO4, 0 . 0 5 % w/ v MgSO4·7H2O, and

0.05 % w/ v NaCl) supplemented with 1 % w/ v glucose and

0.5 % w/ v ammonium sulfate and analyzed for FTIR. The

samples were prepared by freeze-drying overnight .

The surface area of the fungus after 5 days decolorization

in POME was determined using single-point Brunauer, Em-

met, and Teller surface area (Micromeritics Pulse Chemi-

Sorb 2705). The gas mixture was composed of 30 mol%

nitrogen and 70 mol% helium.

Kinetic studies

The kinetics of color sorption by growing cultures of A.

fumigatus was analyzed using different kinetic models in-

cluding pseudo-first order (Lagergren 1898) and pseudo-

second order (Ho and Mckay 1998).

The conformity between experimental data and the

model-predicted values was expressed by the correlation

coefficient, r 2. A relatively high r 2 value indicates that the

model successfully describes the kinetics of adsorption of

color by A. fumigatus.

Results and discussion

Screening and molecular identification for POME

decolorizers

A total of 11 out of 24 fungi were successfully isolated to

decolorize POME, and the best fungus was further selected

for use in the subsequent experiments. In general, the de-

colorization capacity obtained ranged from 27 to 46 % (four

from Ananas comosus, one from dead branches and Musa

sp., and four from wild grass) and the highest was 63 %

(from POME sludge). The results of sequence alignment

based on BLAST analysis revealed that the best fungus for

decolorization was A. fumigatus. The sequence was submit-

ted to the GenBank database and has been assigned the

accession number JF835995.

Screening results of nutrient supplement

Figure 1 shows the four carbon sources (glucose, sucrose,

fructose, and glycerol) that demonstrated the most significant

effect to decolorize POME up to 67 %. There was no signif-

icant difference between glucose and sucrose, as indicated by a

p value of more than 0.05 significance level (data not shown).

POME supplemented with fructose and glycerol gave a slight-

ly low decolorization percentage, while POME supplemented

with CMC only gave a decolorization percentage of up to

27 %. These results were similar to the results of Jin et al.

(2007) who compared glucose, sucrose, and CMC. It was

found that CMC gave the lowest decolorization percentage

of dye industry effluent using A. fumigatus. Since glucose gave

the best POME decolorization (67 %), it was selected for use in

further experiments involving two-level factorial design to

determine optimal conditions for the decolorization of POME.

Table 2 Coded and uncoded values of the experimental variables for

RSM

Independent variables Symbols Coded level

−1 (low level) 0 +1 (high level)

pH A 4.5 5 6.5

Glucose concentration

(% w/ v )

B 0.75 1.0 1.25

Temperature (°C) C 30 35 40



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factors on the percentage decolorization, the three-

dimensional (3D) plots were drawn.

Figure 2a presents the effect of pH and glucose at fixed

temperature (35 °C). As there was an increase in glucose

concentration, the decolorization efficiency was up to the opti-

mum level with a pH of 5.7. There was no significant difference

observed for the glucose concentration ranges from 0.57

until 0.75 % w/ v . The optimum pH for POME decoloriza-

tion using A. fumigatus was at pH 5.7, which was similar

to the result of Sharma et al. (2009) who reported the

optimum pH for decolorization of dye effluent using A.

fumigatus fresinus at pH 5.5. Decolorization was inhibited

when pH was increased from 5.7 to 6.5. This may be due

to the inhibition of fungal growth and thus decreased the

decolorization capacity. Figure 2b presents the interaction

effect of pH and temperature at fixed glucose concentration

(0.57 % w/ v ). As there was an increase in temperature, the

decolorization efficiency was up to the optimum level with

the pH of 5.7. The 3D plot indicated that decolorization

efficiency is more dependent on pH than on temperature.

Experimental results for the biosorption of humic acid using

fungi biosorbents reached the optimum at low pH (Zhou

1992). Another study reported that decolorization of dye

industry effluent by A. fumigatus reached the optimum at

pH 3 (Jin et al. 2007). Figure 2c presents the effect of

glucose and temperature at pH 5.7. Temperature has little

effect on decolorization compared to glucose concentration.

It can be concluded that a small change in pH will bring a

significant change in decolorization, followed by glucose

concentration and finally the temperature. The application

of A. fumigatus for the decolorization of POME seemed to

be a practical approach since it was able to decolorize

POME up to a maximum of 71 % after 5 days of

incubation at 35 °C with shaking (150 rpm) at pH 5.7

supplemented with 2.5 % v / v inoculum and 0.57 % w/ v

glucose.

Decolorization studies

Table 4 summarizes the removal efficiency of color (71 %),

COD (71 %), ammoniacal nitrogen (35 %), total polyphe-

nolic compounds (50 %), and lignin (54 %) after 5 days of

incubation under optimized RSM conditions. The COD,

ammoniacal nitrogen, total polyphenolic compounds, and

lignin in sterile POME (pH 5.7) remained constant with an

increase of color between 4 and 6 % and a slight increase in

pH after 5 days incubation.

Figure 3 shows a similar trend in color, pH, COD,

total polyphenolic compounds, and lignin using A. fumi-

gatus. There is a decrease in pH after 5 days incuba-

tion. This is probably due to the secretion of acidic

metabolites, consequently leading to an increase in the

acidity of the POME. For the fermentation of POME by

Aspergillus niger , citric acid, oxalic acid, and gluconic

acid were produced (Jamal et al. 2007). The release of

acidic metabolites decreases the pH of the culture and

affects the surface charge of the mycelium. At low pH,

high concentrations of protons lead to an increase in

adsorption as the repulsive forces between fungi with

humic acid and lignin were reduced (Zhou and Banks

1993). Besides, the ionization of humic acid and lignin

molecules decrease at low pH and self-aggregation takes

plac e (Belgacem and Gandini 2008) and thus easily

“trapped” by fungi mycelium. This explained why the

adsorption of humic acid and lignin by fungi occurs

best at low pH.

Table 3 ANOVA for the RSM parameters

Term Sum of squares df Mean square F value Prob> F ( p value)

Model 12,273.85 9 1,363.76 157.13


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Fig. 2 a 3D surface plots for

the decolorization of POME as

a function of pH and glucose

with temperature kept at 35 °C.

b 3D surface plots for the

decolorization of POME as a

function of pH and temperature

with glucose concentration kept

at 0.57 % w/ v . c 3D surface plots

for the decolorization of POMEas a function of glucose and

temperature with pH kept at 5.7



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Figure 3b shows a similar trend of color and COD re-

moval during the treatment period. The addition of glucose

was necessary for fungi growth and color removal during

the treatment. The consumption of glucose by A. fumigatus

caused an increase in biomass and thus increased the bio-

sorption surface area. Besides, consumption of glucose and

other compounds in POME causes a decrease in pH which

consequently increases the color and COD removal.

Figure 3c shows the removal of total polyphenolic com-

pounds, lignin, and color during the treatment process. The

correlation analysis (r 2) for color and polyphenolic compounds is 0.9394, whereas for color and lignin is 0.9524.

In other words, lignin and total polyphenolic compounds are

directly proportional to color. Similar results were obtained

from the decolorization of debarking water which was con-

tributed mainly by the lignin content (Kindsigo and Kallas

2009). To the best of our knowledge, there is no study

related to the removal of polyphenolic compounds in treated

Table 4 Reduction in effluent quality parameters using A. fumigatus

Parameter Initial Final Percentage

Color (ADMI) 3,260±41 935±35 71

pH 5.71± 0.02 2.72±0.05 –

COD (mg/L) 2,429±91 703±32 71

Ammoniacal nitrogen (mg/L) 157± 7 102± 4 35

Total polyphenolic compounds

(mg/L)

303±12 151±6 50

Lignin concentration (mg/L) 338± 2 155± 3 54

Fig. 3 Profile of color, pH,

COD, and total polyphenolic

compounds/lignin

concentration versus time at the

optimal condition predicted byRSM. a Plot of color ( green

triangles) and pH ( purple

multiplication sign) versus

time. b Plot of color ( green

triangles) and COD (orange

squares) versus time. c Plot of

color and total polyphenolic

compounds ( purple

multiplication sign)/lignin

concentration (orange squares)

versus time



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POME. The only work reported in the literature was the

removal of polyphenolic compound in anaerobic POME

using Lactobacillus plantarum (Limkhuansuwan and Chai-

prasert 2010). A. fumigatus showed polyphenol removal of

more than ten times as compared to L. plantarum.

Decolorization mechanism

For the growing cultures, desorption of color from fungus

pellet using 0.1 M NaOH produced about 89± 2 % of color

removal from POME. From the results obtained, it may be

inferred that most of the color-causing compounds were

bou nd to the myc eli um via ads orp tion; thi s typ icall y

involves a combination of active and passive transport

mechanism starting with the diffusion of the adsorbed com-

ponent to the surface of the cell (Bayramoğlu and Yakup

Ar ıca 2007). The active transport mechanism generally

involves the use of energy generated by living cells, whereas

the passive transport mechanism is the diffusion of the

colored compounds and is mainly influenced by the affinity between the biosorbent and sorbate (Volesky 2007). Desorp-

tion using NaOH indicates that electrostatic attraction was

the main the active force between the fungi and colored

compounds (Xin et al. 2010) and the resulting adsorption

is reversible in nature (Gupta et al. 2009).

Figure 4 shows that the fungus pellets after desorption

had a highly porous mycelium matrix and their large surface

areas were clean for colored compound uptake (Fig. 5). The

appearance of the hyphae of A. fumigatus implies a very

high capacity for uptake of colored compounds. A porous

structure is very important for colored molecules to be

adsorbed on the fungi. The surface area of A. fumigatus after

5 days decolorization in POME is 6.67 m2/g. This value is

higher than the immobilized A. niger for biosorption of dyes

that is in the range of 2.40 to 3.16 m2/g (Fu and Viraraghavan

2003). This shows that using living A. fumigatus gives a

higher surface area compared with the immobilized fungusfor biosorption of colored compounds. Besides, the scanning

electron microscopy (SEM) image in Fig. 5 shows that the

mycelium still kept a smooth morphology even after adsorp-

tion of color, and this was different from the study of Wang

and Hu (2008) on the adsorption of reactive dye by immobi-

lized growing A. fumigatus beads. Wang and Hu (2008)

reported that the damaged part of the cell walls of A. fumigatus

may be due to the toxicity of the dye in the medium.

The FTIR spectra of A. fumigatus cultured in colorless

mineral salts medium after 5 days decolorization and desorp-

tion are given in Fig. 6. A similar and very strong peak was

observed for fungus before decolorization (3,445.27 cm−1),

fungus after 5 days decolorization (3,435.62 cm−1), and fun-

gus after desorption (3,448.05 cm−1). The broad overlapping

peak of the fungus after 5 days of decolorization might be

due to hydroxyl or amine groups present in the POME.

The appearance of weak bands (2,922.69, 2,922.49, and

2,923.47 cm−1) in all of the samples could be assigned to

the C – H sp3. The medium band for fungus before decol-

orization (1,634.99 cm−1), fungus after 5 days decoloriza-

tion (1,640.60 cm−1), and fungus after desorption

(1,635.00 cm−1) was a consequence of the amide carbonyl

group (C0O amide) and the shifted peak, suggesting its

role in adsorption. The weak band for fungus before

decolorization (1,433.42 cm−1), fungus after 5 days decol-

orization (1,430.86 cm−1), and fungus after desorption

(1,384.82 cm−1) could be attributed to the presence of addi-

tional nitro groups (N0O) in POME. The overlapped band for

fungus before decolorization (1,055.69 cm−1), fungus after

5 days decolorization (1,056.23 cm−1

), and fungus after de-

sorption (1,071.43 cm−1) could be assigned to the – CN

stretching vibration of the chitin – chitosan and protein frac-

tions (Gupta and Rastogi 2008b). The appearance of a bandFig. 4 SEM image of A. fumigatus after desorption at ×1,500

Fig. 5 SEM image of A. fumigatus after decolorization of POME at

×1,500



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for the fungus before decolorization (554.99 cm−1), fungus

after 5 days decolorization (463.20 cm−1), and fungus after

desorption (666.55, 578.42, and 502.57 cm−1) represents the

C – N – C scissoring that is only found in protein structures

(Akar et al. 2009). Significant changes in wave numbers for

the fungus after 5 days decolorization suggested that the

hydroxyl group, C – H sp3, and the amide carbonyl group,

N0O and C – N, could combine intensively with the colored

compound in POME (Gupta and Rastogi 2008c).

Kinetic studies

The correlation analysis values for pseudo-first-order

and pseudo-second-order kinetics are 0.9892 and 0.012,

respectively. The pseudo-first-order kinetics had the

highest r 2 values, as shown in Fig. 7, with the rate

constant (k ) of 0.1044. The pseudo-first-order kinetics

also had the highest precision between the experimental

qe

and calculated qe

compared to the pseudo-second-

order kinetics. Thus, the pseudo-first-order kinetics

model was taken as the best fit equation to describe

the sorption mechanism of color. The pseudo-first-order kinetics considers the rate of adsorption to be propor-

tional to the number of unoccupied sites. The applica-

bility of the pseudo-first-order kinetics shows that the

adsorption rate depends on the ADMI value. Numerous

studies reported on the pseudo-first-order kinetics for

the sorption of dyes such as the sorption of acid dyes

onto chitosan (Wong et al. 2004) and sorption of hex-

avalent chromium using Acinetobacter junii (Paul et al.

2012). However, to the best of our knowledge, this is

the first report on pseudo-first-order kinetics for the

absorption of color using growing fungi where the bio-

mass of the fungi changed with time.

Conclusions

The results of this study indicated that growing cultures

of A. fumigatus can be used for the decolorization of

POME to a maximum of 71 % in 5 days. Optimization

studies indicated that pH 5.7, incubation temperature of

35 °C, and inoculum size of 2.5 % v / v with the addition

of glucose 0.57 % w/ v were optimal for maximum

decolorization of POME. This is the first reported work

on the application A. fumigatus for the decolorization of

POME. These results suggested that the decolorization

process mediated by A. fumigatus has potential applica-

tions for treatment operations through the biosorption

and biodegradation processes. Further research should

be carried out in nonsterile wastewater and scale-up in

a bioreactor.

Fig. 7 Pseudo-first-order kinetic modeling of the decolorization of

POME by A. fumigatus

Fig. 6 FTIR spectra for a fungus before decolorization, b fungus after

5 days decolorization, and c fungus after desorption using 0.1 M NaOH



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Acknowledgments The authors would like to express their appreci-

ation to the Ministry of Sciences and Innovation Malaysia (National

Science Fellowship) and Universiti Teknologi Malaysia for the finan-

cial support. The authors also would like to thank the local company

Johor for sampling of the wastewater.

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Optimization of Decolorization of Palm Oil Mill Effluent (POME) by Growing Cultures of Aspergillus Fumigatus Using Response Surface Methodology