Indonesian
Journal of Biotechnology, June, 2014
Margino et al.
Vol. 19, No. I.J.
1, pp.56-63
Biotech.
Poly-β-Hydroxybutyrate (PHB) Production By Amylolytic Micrococcus sp.
PG1 Isolated From Soil Polluted Arrowroot Starch Waste
Sebastian Margino1, Erni Martani1 and Andriessa Prameswara2,
1
Department of Agricultural Microbiology, Faculty of Agriculture, Universitas Gadjah Mada, Yogyakarta,
Indonesia
2
Study Program for Biotechnology, Graduate School of Universitas Gadjah Mada, Yogyakarta,
Indonesia
Abstract
Poly-β-hydroxybutyrate (PHB) production from amylolytic Micrococcus sp. PG1. Poly-β-hydroxybutyrate
(PHB) is an organic polymer, which synthesized by many bacteria and serves as internal energy. PHB is
potential as future bioplastic but its price is very expensive due to glucose usage in PHB industry. The
development of PHB production using starch as an alternative carbon source has been conducted to reduce
the dependence of glucose in PHB production. In this study, amylolytic bacteria from arrowroot processing
site were screened quantitavely based on amylase specific activity and PHB producing ability. The result of the
study showed that among of 24 amylolytic isolates, 12 isolates of them were able to accumulate PHB ranged
from 0,68-11,65% (g PHB/g cdw). The highest PHB production from substrate arrowroot starch was PG1 and
after optimization resulted in increasing of PHB production up to 16,8% (g PHB/g cdw) 40 hours incubation
time. Based on morphological, biochemical and physiological characters, the PG1 isolate was identified as
Micrococcus sp. PG1. Result of the FTIR analysis of produced polymer by Micrococcus sp. PG1 was indicated
as poly-β- hydroxybutyrate (PHB)
Keywords: Poly-β-hydroxybutyrate (PHB), indigenous amylolytic bacteria, arrowroot starch
production (Koller et al., 2010). Among those,
starch is potential to develop as alternative
carbon source for PHB production because it
is cheap, vary and many in supply (Koller et
al., 2010; Gonzalez-Garcia et al., 2011).
Research of starch as carbon source for
PHB production has been explored during
years with various of bacteria. Margino et al.
(2000) use tapioka starch to produce PHB by
Bacillus and Pseudomonas while Yanti (2011)
use sago starch and isolate Bacillus PSA 10.
The results suggested that there is possibility
to use other starches as carbon source for PHB
production. One of alternatives is arrowroot
(Maranta arundinaceae) starch which has
carbon (C) content 57,69%, nitrogen (N)
content 0,33%, phosphorous (P) content
0,004% and kalium (K) content 0,35 %.
In order to optimize arrowroot starch
as carbon source in PHB production,
exploitation of amylolytic bacteria which can
Introduction
Poly-β-hydroxybutyrate (PHB) is a
polymer, which naturally synthesized by
many bacteria and serves as internal energy.
PHB is biodegradabel and biocompatible
(Chen, 2009) and its physical and chemical
characteristics are similar to polypropylene
(Flieger et al., 2003; Reddy et al., 2003). PHB
is potential as future bioplastic but its price
is very expensive due to glucose usage in
PHB industry. The development of PHB
production using alternative carbon source
such as starch, canola industrial wastes,
dairy wastes, and bit has been conducted to
reduce the dependence of glucose in PHB
*
Corresponding author:
Sebastian Margino. Faculty of Agriculture,
Universitas Gadjah Mada, Yogyakarta, Indonesia.
Email: margino@ugm.ac.id
56
Margino et al.
I.J. Biotech.
also synthesize PHB is required. Hoping that
by optimization measures the production
of PHB from arrowroot starch be more
effective and efficient. Amylolytic bacteria
which can hydrolyzed arrowroot starches
are potential to be found from arrowroot
processing starch. Therefore, screening of
indigenous amylolytic bacteria is done to get
the potential isolate.
(pH 6.5). The mixture was then incubated
at 37°C for 1 hour. Reaction was stopped by
adding 1.5 ml of I N acetic acid followed by
0.5 ml of Lugol’s iodine. Absorbance was
read at 700 nm (Lee and Fujio, 1997). The
alpha-amylase activity was calculated by
(Espino and Tambalo, 1997) :
DUN/ml = [(R0-R1)/R0] [faktor
pengenceran] [10]
DUN/ml = Denitrinizing unit per ml
R0
= Blank absorbance
R1
= Isolate absorbance
Materials And Methods
Isolation of bacteria from starch production
site
Three different samples being liquid
waste, solid waste and raw arrowroot
starch were collected from arrowroot starch
processing site in Sendang Sari, Kulon
Progo, Yogyakarta, Indonesia. Ten grams of
each samples were serially diluted in 90 ml
distilled water and placed onto arrowroot
starch nutrient agar plates (Joetono et al.,
1978). Cultures were incubated at room
temperature for 24-72 hours. Various colonies
of different morphologies were individually
picked and sub cultured on nutrient agar
plate added by arrowroote starch.
Determination of crude enzyme protein
was measured by Bradford method (Bradford,
1976). The specific activity of amylase was
determined by dividing the volumetric
activity (DUN/ml) by the protein content
(mg/ml).
Production of PHB was quantitatively
measured by using Ramsay media (6.7
g of Na 2HPO 4.7H 20; 1.5 g of KH 2PO 4; 1.0
g of (NH 4)2SO 4; 0.2 g of MgSO 4.7H 20; 60
mg of ferrous ammonium citrate; 10 mg
of CaCl2.2H20, and 1 ml of trace-element
solution. Each liter of trace-element solution
contained 0.3 g of H3B03; 0.2 g of CoCl2.6H20;
0.1 g of ZnSO4.7H20; 30 mg of MnCl2.4H20; 30
mg of NaMoO4.2H2O; 20 mg of NiCl2.6H20
and 10 mg of CuSO4.5H20)(Ramsay et al.,
1990) with arrowroot starches as carbon
sources 1% (w/v), inoculum concentration
5% (v/v), temperature 30°C, pH 7, agitation
rate 125 rpm and incubation time 72 hours.
The culture then subjected to centrifugation
for 20 minutes at 3,000 rpm (Hahn et al.,
1995). Extraction of PHB from bacteria cells
was done by N-hexane acetone-diethyleter
method (Senior et al., 1972). Pellet then were
changed to crotonic acid by adding 3 ml of
sulfuric acid and boiled it at 100°C for 10
minutes. The PHB content was measured by
U.V. spectrophotometer at 235 nm.
Microorganisms screening for amylolitic
activity, amylase activity and PHB
activity
Determination of amylolytic activity
on starch agar media was based on the
presence of clear zone around the bacterial
colony upon flooding with I2KI solution.
The hydrolytic ability value is the ratio of
hydrolysis zone (clear zone) diameter (cm)
formed by a bacterium colony and its colony
diameter (cm) (Jamilah et al., 2009).
Amylolytic isolates were grown in
Ammonium Sulphate Starch media (Fred and
Waksman, 1928) with inoculum concentration
5% (v/v) and were incubated at agitation
rate 125 rpm, temperature 30°C for 72 hours
(Lee and Fujio, 1997). Crude enzymes were
obtained by centrifugation at 4,000 rpm,
temperature 4°C for 20 minutes. One ml of
the crude enzyme was added to one ml of 2%
arrowroot starch in 0.1 M phosphate buffer
Growth optimization
The selected isolate was optimized
for PHB fermentation condition in terms of
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Margino et al.
I.J. Biotech.
inoculum concentration (2.5; 5; 10; 15% (v/v)),
nutrients concentrations such as arrowroot
starch (2.5; 5; 10; 20 and 30 g/l), (NH4)2SO4(0;
0.5; 1; 1.5 and 2 g/l), Na2HPO4.7H20 (0; 2.3;
4.5; 6.7 and 8.9 g/l0) and KCl (0; 0.5; 1; 1.5;
2 g/l); and environmental condition such as
pH (5; 6; 7 and 8), incubation temperature (30;
37 and 40°C) and agitation rate (75; 100; 125
and 150 rpm). All optimization parameters
were observed in shake flask culture.
characters in Bergey’s Manual of Determinative
Bacteria 9th (Holt et al., 1994).
The polymer produced by the selected
isolate was extracted by incubated cell mass
with H2O2 5% (v/v) and chloroform (1:1) for 2
hours. Pellet was harvested by centrifugation
4,000 rpm for 20 minutes. The bottom part
of supernatant was pour on the petri dish to
let the chloroform evaporate. The extracted
polymer was analyzed by Fourier Transform
Infrared spectroscopy (FTIR).
PHB production in fermentor (batch)
The production of PHB by selected
isolate was carried out in 2 l fermentor
with a 1.5 l working volume. The best
condition from optimization steps was
applied. The agitation rate and temperature
was maintained stable. pH of the medium
was checked before inoculation. Aeration
for this condition was 1.6 l/minute. Samples
were withdrawn aseptically at 4 hourly
intervals. PHB concentration, cell dry weight
(cdw), glucose level and residual starch was
observed.
Results and Discussion
Isolation and screening of amylolytic
bacteria producing PHB
Twenty four amylolitic bacteria were
isolated from arrowroot processing site.
Twelve among them which had hydrolytic
ability ranging from 2.50-6.00 were screening
for amylase activity and PHB production
(Table 1). The amylase specific activity ranges
from 111.85-2121.52 DUN/mg and PHB
productivity capacity ranged from 0.68-11.65%
(g PHB/g cdw) for those isolates. Based on this
data, PG1 was chosen as the most potential
isolate. It has amylolytic activity 2121,52 DUN/
mg and PHB production 11.65%.
Genus of selected isolate identification and
FTIR analysis of the polymer
The selected isolate was further
identified based on morphology, biochemical
and physiological characteristics (Joetono et
al., 1980). The characters was compared with
Growth optimization
The best conditions for PHB production
by the isolate PG1 was achieved at 5% (v/v)
Table 1. Hydrolytic ability, amylase activity and PHB production of several amylolytic isolates from arrowroot
processing site
Isolate
code
Hydrolytic
ability
ABG 21
ABG 22
AG 3
AG 4
AG 7
AG 8
LC 32
PG 8
PG 1
PG 4
PG 5
PG 6
3.08
3.20
2.54
5.95
3.66
3.16
3.k11
3.5
3.71
4.48
3.54
2.57
Amylase
activity
(DUN/ml)
86.59
86.64
24.56
30.26
27.07
46.34
86.90
16.23
95.74
89.77
89.94
24.05
Protein
content (mg/
ml)
0.272
0.319
0.169
0.163
0.143
0.154
0.297
0.145
0.045
0.200
0.081
0.144
Spesific Activity of
Amylase (DUN/mg
protein)
318.18
271.55
145.28
186.03
189.35
300.80
292.86
111.85
2,121.52
448.80
1106.31
167.53
58
PHB
content
(g/l)
0.0134
0.0050
0.0085
0.0078
0.0147
0.0118
0.0090
0.0398
0.0816
0.0130
0.0120
0.1025
Cell dry
weight
(g/l)
0.58
0.69
0.80
0.38
0.68
0.52
1.33
0.76
0.70
0.67
0.57
1.29
PHB (%)
2.31a
0.72a
1.06a
2.08abc
2.16ab
2.29abc
0.68a
5.23de
11.65g
1.96ab
2.09ab
7.98f
Margino et al.
I.J. Biotech.
Figure 1. Effect of inoculum and nutrient concentration on PHB production
inoculum concentration, arrowroot starch at
5 g/l, (NH4)2SO41 g/l, Na2HPO4.7H20 6,7 g/l
and KCl 2 g/l (Figure 1). Whereas the best
environmental condition in term of initial pH
at 7, temperature at 30°C and agitation speed
at 125 rpm (Figure 2). After optimization,
PHB production of PG1 was increased from
11,65 to 16,8 %.
PG1 isolate had the highest rate of PHB
production by 6% at inoculum concentration
5 % (Figure 1). Inoculum concentration is
important to be studied because inoculum
concentrations affect the efficiency of PHB
production and the incubation time (Yamane
et al., 1996; Cetin et al., 2006). While for the
nutrient concentration, all parameters were
similar with the standart Ramsay’s medium,
except the KCl concentration. PG1 achieved
9.6% PHB when used 5 g/l arrowroot
starch, and respectively 13.7% and 14.4 % of
PHB with 6.7 g/l Na2HPO4.7H20 and 1g/l
(NH4)2SO4. For the K component, PG1 isolate
required 2 g/l KCL to get the best production
of PHB. It was suggested that PG1 isolate
required more K for PHB production.
The effect of temperature was studied
to find out the best temperature to support
production PHB by PG1. PG1 required
incubation temperature at 37 °C to achieved
12 % of PHB. Shi et al. (2001) mentioned that
incubation temperature at 37 °C significantly
induced the expression of gene which
responsible for PHB production. Bacillus
megaterium PSA 10 also need incubation
temperature at 37 °C for the PHB production
(Yanti, 2011).
PG1 produced 14.9 % PHB when
incubated with agitation rate 125 rpm.
Agitation rate below and above 125 rpm
caused a decrease in PHB production,
suggest that this agitation rate served the best
condition for PG1 in using starch as carbon
source for growth and PHB production.
In terms of initial pH, our result (Figure
2) showed consintency with Palleroni and
Palleroni (1978) who recommended a pH range
of 6.0 to 7.5 for microbial growth and PHB
production. Wei et al. (2011) also showed the
best PHB production by Cupriavidus taiwanensis
at initial pH 7. PG1 achieved the best PHB
production by 16.8 % at initial pH 7.
Production of PHB in fermentor
Optimization result showed that PG1
isolate could produce highest PHB 37 mg/L
and cell dry weight 850 mg/L, respectivelly,
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Margino et al.
I.J. Biotech.
Figure 2. Effect of environmental condition on PHB production
Figure 3. Time course of PHB production by Micrococcus sp. PG1
for 40 hours incubation time (Figure 3). The
PHB production sharply increase when the
level of starch was sharply decrease. This
condition was linear with (Anderson & Dawes,
1990) that mentioned the production of PHB
occurred when the nutrients is unbalanced
because of the lack of carbon source. This
result showed that PG1 synthesized PHB
since exponential phase. PHB production
during exponential phase means the PHB
production is growth associated (Lee, 1996;
Grothe et al., 1999).
Identification of PGI Isolate
Based on the morphological,
biochemical, and physiological characters
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Margino et al.
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(a)
(b)
Figure 4. FTIR spectroscopy of the extracted polymer synthesized by PG1 (a) and PHB standard (b)
PGI isolate was identified as Micrococcus sp.
PG1 (data unpublished).
to specific rotations around carbon atoms
specific to certain functional groups (Figure
4). The peak at 1728.22 cm -1 corresponds
to ester carbonyl (C=O) stretch of the ester
group present in the molecular chain of
highly ordered crystalline structure. The peak
of at 1280.73 cm-1corresponds to -CH group
(Figure 4). These peaks are corresponding
to the peaks obtained for the standard PHB
(Sigma) at 1728.22 cm -1 and 1280.73 cm -1
FTIR analysis
FTIR analysis of polymer produced by
PG1 using arrowroot starch as subtrates was
investigated along with PHB obtained from
commercial source (Sigma). FTIR spectra of the
extracted polymer showed the intense peaks
1728.22 cm-1and 1280.73 cm-1 corresponding
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Margino et al.
I.J. Biotech.
exactly confirming that the extracted polymer
was poly-β-hydroxubutyrate (PHB) (Hong et
al., 1999).
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Conclusion
The best condition for PHB production
by the isolate PG1 was achieved at 5 % (v/v)
inoculum concentration, arrowroot starch 5
g/l (w/v), (NH4)2SO41 g/l, Na2HPO4.7H20
6,7 g/l and KCl 2 g/l; whereas the best
environmental conditions in term of initial
pH was 7, temperature 37°C and agitation
speed 125 rpm. Optimization of PG1 resulted
in increasing of PHB production up to 16.8%
(g PHB/g cdw) for 40 hours incubation time.
FTIR analysis of the polymer indicated that
produced polymer by Mirococcus sp. PG1 was
a poly-β-hydroxybutirate.
Acknowledgement
This research was funded by “Hibah
Kompetensi” under the Minister of National
Education, Republic of Indonesia under the
PI: Prof. Ir. Sebastian Margino, Ph.D.
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