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Agrowastes of banana peels as an eco-friendly
feedstock for the production of biofuels using
immobilized yeast cells
To cite this article: R Abdulla et al 2022 IOP Conf. Ser.: Earth Environ. Sci. 1103 012022
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Natural Disaster Seminar 2019
IOP Conf. Series: Earth and Environmental Science 1103 (2022) 012022
IOP Publishing
doi:10.1088/1755-1315/1103/1/012022
1
Agrowastes of banana peels as an eco-friendly feedstock for
the production of biofuels using immobilized yeast cells
R Abdulla1*, Q Johnny1, R Jawan1 and S A Sani1
1 Faculty of Science and Natural Resources, Universiti Malaysia Sabah, 88400, Kota
Kinabalu, Malaysia
*Corresponding author’s e-mail: rahmahabdulla@gmail.com
Abstract. Liquid biofuels such as bioethanol is a promising renewable fuel as it can be
produced from various biomass wastes as feedstocks. The concept of waste to wealth approach
is inevitable for bioethanol production. In Malaysia, banana peels are one of the largest
agricultural wastes found in the local market. Thus, in this study, banana peels were used as a
feedstock to produce bioethanol through fermentation using immobilized yeast cells. For
higher yield of bioethanol, optimization parameters were conducted for both dilute acid
hydrolysis and fermentation process. First, the banana peels were sliced and oven-dried at 70oC
for 24 h before being ground to fine powder. Then, the samples were subjected to dilute acid
hydrolysis. Parameters such as concentration of H2SO4, temperature and time were optimized
during the hydrolysis. Higher amount of reducing sugar was obtained at 0.10 M H2SO4, at 90oC
for 20 min with 5.190 mg/mL, 5.196 mg/mL and 5.306 mg/mL respectively for the hydrolysis
process. Yeast Saccharomyces cerevisiae was immobilized using 3% (w/v) of sodium alginate
and 2% (w/v) calcium chloride using entrapment technique, in the form of beads. These
immobilized beads were added into the fermentation medium together with the optimized
pretreated hydrolysate of banana peels. Parameters such as cells loading (weight of beads), pH,
temperature and time were also optimized in the fermentation process. From the results, it was
found out that the optimized parameters of 9g of cells loading, pH 5, at 30oC for 24 h utilized
more sugar during fermentation process based on the absorbance reading.
1. Introduction
The world is very dependent on fossil fuels which dominates the energy industry. Fossil fuels are
crucial for the process of urbanization and industrialization, mainly for production of fuel and
electricity [1]. However, due to shortage of energy sources, concern in searching for alternative fuels
are increasing to reduce the consumption of non-renewable energy sources by using biofuels. Liquid
biofuesl such as bioethanol is expected to be one of the dominating renewable fuels in various
developing sectors replacing the fossil fuels as they are sustainable, cost-effective and safer to use [2].
Bioethanol has many advantages which enables it to become one of the most promising alternative
fuel. According to Niven (2005), the government of India has introduced alcohol as automotive fuel
blending 5% of ethanol with petrol [3]. Alcohols have been used as fuels since the inception of the
automobile. Currently, fuel ethanol blends are successfully used in all types of vehicles and engines
that require gasoline [4]. Recently, new interest has focussed on feedstocks for bioethanol production
Natural Disaster Seminar 2019
IOP Conf. Series: Earth and Environmental Science 1103 (2022) 012022
IOP Publishing
doi:10.1088/1755-1315/1103/1/012022
2
using sugar-based, starchy and lignocellulosic biomass. The use of agricultural wastes as raw material
is said to be particularly convenient because it is inexpensive, abundant and thus able to reduce the
cost of production [5;6].
In Malaysia, banana is one of the most highly produced tropical fruit and widely cultivated as the
total planted area of banana had reached 33,704.2 ha in year 2001 [7]. The more production of banana
results in the increase of wastes being generated. According to scientists, approximately one ton of
wastes are produced for every ten ton of bananas cultivated [8]. Banana biomass comprises of three
main items which are the rejected fruits, the peels and the pseudostems, which could be employed in
bioethanol production [9;10]. Several attempts have been made to utilize banana waste as a substrate
for bioethanol fuel production [11;12;13;14]. Tan et al. (2019) investigated the potential of
fermentable sugars found in banana frond juice for production of bioethanol by using S. cerevisiae
yeast [14]. Meanwhile, Ingale et al. (2014) exploited the banana pseudostems as a feedstock in solid
state fermentation process for bioethanol production using S. cerevisiae NCIM 3570 [12].
S. cerevisiae and S. bayanus var. Uvarum are two types of yeasts that are important for
fermentation process [15;16]. An ideal yeast or microorganism is important to obtain optimum yield of
bioethanol. It must have rapid fermentative potential, improved flocculating ability, appropriate
osmotolerant, enhanced ethanol tolerance and also good thermo tolerance to efficiently ferment the
sugars for bioethanol production [17;18]. In this study, immobilized yeast cells of S. cerevisiae will act
as a biocatalyst with calcium alginate entrapment technique in order to increase the fermentation
productivity. According to El-Dalatony et al. (2016), immobilized yeast cells enabled repetitive
ethanol production for 7 cycles resulting in a fermentation efficiency up to 79% for five consecutive
cycles for microalgal biomass fermentation using immobilized S. cerevisiae [19].
Thus, this research is aimed to optimize the bioethanol production of banana peels using
immobilized yeast S. cerevisiae Type II. Significant effect of parameters such as concentration of
H2SO4, temperature, time, cell loading and pH will be optimized during the process of pretreatment
and fermentation of sugar sources from banana peels.
2. Materials and Method
2.1. Collection and preparation of Banana peels
Musa acuminata Colla cv Berangan banana peels were collected from local market in Sabah. The
peels were washed with tap water and cut into a smaller slices. Then, it was oven-dried at 70 oC for 24
h. After drying, the dried samples were ground to fine powder by using a laboratory blender [20]. The
powdered banana peels were stored in a sealed plastic bag until further use. Figure 1 shows the banana
peels preparation method.
Figure 1. Preparation of banana peels, (A) Musa acuminata Colla cv Berangan, (B) fresh banana
peels, (C) Oven dried banana peels and (D) Powder form of banana peels.
A
B
C
D
Natural Disaster Seminar 2019
IOP Conf. Series: Earth and Environmental Science 1103 (2022) 012022
IOP Publishing
doi:10.1088/1755-1315/1103/1/012022
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2.2. Optimization of acid hydrolyis pretreatment
A total of 12 experiments were done for the acid hydolysis pretreatment of banana peel powder with
its respective parameters. The parameters selected were concentration of H2SO4 (0.10 M - 0.20 M),
temperature (70 oC - 130 oC) and hydrolysis time (10 min - 40 min). The baseline was set at
concentration of 0.15M H2SO4, temperature at 90 °C for 20 min. The samples were optimized based
on the selected parameters in order to gain higher yield of reducing sugar. Then, the hydrolysate
obtained were separated by a fabric filter to get the liquid phase product. The reducing sugar content
of the hydrolysate was analyzed using dinitrosalycylic acid (DNS) method [21;22].
2.3. Analysis of reducing sugar concentration
The reducing sugar obtained was estimated using 3,5 dinitrosalycylic acid (DNS) method. DNS
reagent was prepared by dissolving 30 g of potassium sodium tartrate in a 50 mL of distilled water and
1 g of 3,5 dinitrosalycylic acid in a 20 mL of 2 M sodium hydroxide solution. The two solutions were
mixed and top up to 100 mL with distilled water to formed the DNS reagent. Standard curve was
plotted based on the absorbance reading against the glucose concentration. For estimation of reducing
sugar in this study, 1 mL of sample was pipetted into a test tube. Then, the sample was top up with 3
mL of distilled water before adding 1 mL of DNS reagent into the test tube. The test tube was heated
in a boiling water bath for 5 min after covered with cotton. The test tube was allowed to cool at room
temperature and the absorbance was measured at 540 nm wavelength against the blank. Absorbance
reading was compared with the standard curve and concentration of the glucose in the sample was
determined.
2.4. Preparation of inoculum
Yeast strain S. cerevisiae Type II bought from Sigma-Aldrich (Missouri, USA) was used in this
experiment. The yeast strain was cultured on a YPG agar and incubated at 37 oC for 48 h in an
incubator. Then, a loop full of yeast cell was inoculated in 100 mL of sterile YPG medium. Yeast
inoculum was prepared at 30 oC, 200 rpm for 15 h in an incubator. The yeast cells were harvested and
centrifuged aseptically at 2000 rpm for 20 min. The supernatant was discarded while the pellets were
washed twice and used for cell immobilization.
2.5. Immobilization of S. cerevisiae Type II
For yeast cell immobilization, 3% (w/v) of sodium alginate solution was prepared by dissolving 3 g of
sodium alginate in 100 mL sterile distilled water. The solution was autoclaved at 121 oC for 15 min.
Then, 100 mL of yeast slurry prepared was added to the sodium alginate solution. The mixtures
obtained were extruded dropwise with sterile syringe into a gently stirred 2% (w/v) calcium chloride
(CaCl2) solution to form beads. The beads formed were left for 4 h for stabilization. Finally, the beads
were stored at 4 oC in CaCl2 solution until further use.
2.6. Optimization of fermentation for bioethanol production
Optimization of various process conditions for the fermentation were carried out in this study to
investigate its influence on the bioethanol yield. The selected parameters were temperature (30 oC, 35
oC, 40 oC), pH value (4, 5, 6) and fermentation time (24 h, 48 h, 72 h). The baseline parameters was set
at 30 oC, pH 6 for 24 h based on a study by Singh et al. (2014) [23]. The 40 mL of banana hydrolysate
with the highest glucose content and the immobilized beads were added into the fermentation medium
at different cell loading, temperature, pH and time. The ethanol content in the hydrolysate was
determined based on the amount of reducing sugars consumed during the fermentation. The amount of
reducing sugar was determined based on the absorbance reading measured at wavelength of 540 nm.
Absorbance reading of the sample was compared with the standard curve and concentration of the
reducing sugar in the sample was determined. Theoretically, the higher the amount of reducing sugars
consumed, the higher the bioethanol content that can be produced from the sample.
Natural Disaster Seminar 2019
IOP Conf. Series: Earth and Environmental Science 1103 (2022) 012022
IOP Publishing
doi:10.1088/1755-1315/1103/1/012022
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3. Results and Discussion
3.1. Banana peel samples
During the samples preparation, banana peels were cut into smaller parts. The reduction in size of the
peels caused the breakdown of the long polymer chain of the bananas into shorter polymer chain. This
also increase its amorphous region, thereby the degree of crystallinity of the lignocellulosic materials
are reduced [24]. It was also oven dried at 70 oC to prevent contamination from occur and higher
ethanol yield is produced [25;21]. Research by Mohapatra et al. (2010) stated that high glucose
concentration found in banana petiole or frond [26]. According to Tran et al. (2015), the amount of
cellulose contents of banana peels were higher, which is about 9.5 %. Moreover based on the study
conducted, the total amount of reducing sugar in banana peels are estimated to be around 1.08 mg/g
[27]. Due to the high amount of cellulose and reducing sugars in banana peels, it was chosen as a
feedstock in this study.
3.2. Acid hydrolyis pretreatment of banana samples
In pretreatment process, the matrix of cellulose and lignin should be broken down in order to reduce
crystallinity degree of cellulose [24]. Dilute acid hydrolysis is one of the best pretreatment method for
lignocellulosic biomass [28]. It is relatively economical and environmentally-friendly compared to
concentrated acid hydrolysis [29]. Moreover, it also solve the problems related to toxicity, acid
recovery and had better results at solubilizing the hemicellulose [30]. Type and composition of the
lignocellulosic material also determine the release of reducin sugar during acid hdrolysis [31]. Sirkar
et al. 2008 stated that for fruit waste such as banana peels, acid pretreatment is the best method to get
higher yield of fermentable sugar [32].
3.3. Pretreatment optimization
Dilute acid hydrolysis is affected by a number of variables, including hydrolysis time, temperature,
solid/liquid ratio and concentration of acid [33;29]. The acid in hydrolysis act as catalyst, but at
specific condition it could be inhibitor and thus decreasing the sugar yield produced. Hence,
optimization are crucial in order to obtain optimal condition for highest yield of reducing sugar. In this
study, parameters involving concentration of H2SO4, time and temperature were optimized.
3.3.1. Effect of concentration of H2SO4. In this study, the influence of H2SO4 concentration on
hydrolysis process is studied in regards to amount of reducing sugar produced. Three different
concentration; 0.10 M, 0.15 M and 0.20 M produced 5.190 mg/mL, 1.075 mg/mL and 0.055 mg/mL
reducing sugar respectively. Based on Figure 2, the highest amount of reducing sugars produced is
using 0.10 M of H2SO4 concentration with 5.190 mg/mL. Further increase in H2SO4 concentration
resulted in substantially decrease in the amount of sugar consumed. Higher absorbance reading was
recorded using a more diluted H2SO4 of 0.10 M. This showed that hydrolysis with low concentration
of H2SO4 produced higher amount of sugar compared to higher concentration. Previous report by Girio
et al. (2010), stated that the suitable range concentration of H2SO4 are in the range of 0.5 % to 1.5 %
[34]. Hence, 0.10 M of H2SO4 was found to be optimum concentration for hydrolysis reaction of
banana peels. In this optimization step, it was proved that even with a very low concentration of acid, a
relatively high yield of reducing sugars could be obtained. The results of this study was similar to
research investigated by Nurfahmi et al. (2016) using empty fruit bunch [35].Through this study,
banana peels can be said to be one of the potential substrates in producing bioethanol because of its
high content of glucose after pretreatment with dilute acid hydrolysis. Besides, the low acid condition
in dilute acid hydrolysis was said to give more profits for the pre-treatment steps as the cost for the
whole process can be reduced.
B
C
Natural Disaster Seminar 2019
IOP Conf. Series: Earth and Environmental Science 1103 (2022) 012022
IOP Publishing
doi:10.1088/1755-1315/1103/1/012022
5
0
1
2
3
4
5
6
7
0.08 0.1 0.12 0.14 0.16 0.18 0.2 0.22
Concentrat ion of acid (M)
Amo unt of reduci ng sugar s (mg/ml )
Figure 2. Effects of H2SO4 concentration on amount of reducing sugar.
3.3.2. Effect of time. In this study, different hydrolysis time (10, 20, 30 and 40 min) is used in the
optimization process. The absorbance reading was measured and used to calculate the amount of
reducing sugars in each experiments. According to Figure 3, amount of reducing sugar produced is
increased until 20 min and then decline after 20 min. High amount of reducing sugar is achieved at 20
min with 5.196 mg/mL which is higher compared to 10, 30 and 40 min of hydrolysis time. When the
hydrolysis time is longer than 20 min, the sugar yield was slightly decreased. This most probably due
to the presence of the inhibitors after a specific time. Some of the compound produced during
hydrolysis might act as an inhibitor and thus resulting in low yield of glucose [36]. In Nurfahmi et al.
(2016), the palm empty fruit bunch (PEFB) which undergo acid hyrolysis pretreatment managed to
produce optimum amount of total sugars of 122.17 mg/L at concentration H2SO4 0.5 % with reaction
time 30 min [35]. However, in this study, optimum condition for hydrolysis reaction is 20 min.
4
4.5
5
5.5
010 20 30 40 50
Time (minutes)
Amo unt of reduci ng sug ars (mg/m l)
Figure 3. Effect of time on amount of reducing sugar.
3.3.3. Effect of temperature. The study is carried out to determine the significant influences of
temperature on hydrolysis process at 70 oC, 90 oC, 110 oC and 130 oC. The absorbance reading was
measured and the amount of reducing sugars for each temperature is calculated using the standard
curve of glucose. From Figure 4, the highest amount of reducing sugar produced is at 90 oC with
5.306 mg/mL. At 70 oC, the reducing sugar produced is the lowest with 4.329 mg/mL. This indicated
that hydrolysis reaction still occur at 70 oC, but not efficient enough to convert large amount of
cellulose into reducing sugars. Beyond 90 oC, the reaction rate decreases with an increase in
temperature at 110 oC and 130 oC. At high temperature, the reaction rate of hydrolysis of banana peels
was slowly decreases. Temperature has a significant effect on the yield of hydrolysis in which it
influence the hydrolysis rate of reaction [37]. In previous research, Yang and Wyman (2008) reported
that mild temperature led to the significant recovery of sugars while hydrolysis reaction done at high
temperatures were reported to cause the reducing sugars to be further degraded into smaller molecules
and thus decreasing the yield [38]. Temperature directly affected the degradation of sugars into
inhibitors and at the same time will influence the microbial metabolism [39].
Natural Disaster Seminar 2019
IOP Conf. Series: Earth and Environmental Science 1103 (2022) 012022
IOP Publishing
doi:10.1088/1755-1315/1103/1/012022
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4
4.5
5
5.5
6
50 70 90 110 130 150
Temper ature (°C)
Amo unt of reduci ng sug ars (mg/m l)
Figure 4. Effect of temperature on amount of reducing sugar.
3.4. Immobilization of S. cerevisiae Type II
Yeast S. cerevisiae Type II collected was mixed with 3% (w/v) of sodium alginate for immobilization
process by entrapping the yeast cells in 2% (w/v) calcium chloride solution. Uniform spherical beads
were formed with the mean diameter of 3 mm. Sizes of the beads produced by the immobilizaton of S.
cerevisiae Type II by entrapment mehod as shown in Figure 5. From the process, diameter of beads
formed were 2 mm to 4 mm. In this study, entrapment technique was used to immobilized the yeast
cells in calcium alginate. Entrapment of yeast cells is a rapid and easy process. According to
Colagrande et al. (1994), calcium alginate gels are often used in cell entrapment and it also considered
to be suitable carrier in alcoholic fermentation [40]. Immobilization method in this study was
conducted by using 3% of sodium alginate and 2% calcium chloride. Most of the studies that related to
immobilization in beads, suggested that 2% to 3% of sodium alginate is the optimum concentration.
Calcium chloride concentration play a vital role in membrane thickness. Wojcik et al. (2013) reported
that the thickness of the membrane increase with a concentration of calcium chloride [41]. The process
of gelation of beads (spherical shape) is started when the sodium alginate (anionic alginate) with yeast
suspension was dropped to cationic solution that containing calcium ions and resulting in the
formation of a membrane. Smaller size of beads are generally preferable due to the favourable mass
transfer characteristics for the entrapped cells [42].
Figure 5. Immobilized S. cerevisiae Type II beads (A) Round shape beads used for fermentaion
process and (B) Beads visualized under Dino-Lite Microscope.
3.5. Optimization of Fermentation process by using immobilized S. cerevisiae Type II
Fermentation process was carried out using optimized banana hydrolysate and the immobilized beads
of S. cerevisiae Type II yeast. Fermentation processes were optimized by varying the cells loading
(weight of beads), pH, temperature and fermentation time. In this study, bioethanol content in the
hydrolysate was determined based on the amount of reducing sugars consumed during the
fermentation process. The higher the amount of sugar consumed, the higher the bioethanol content.
3mm
A
B
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doi:10.1088/1755-1315/1103/1/012022
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3.5.1. Effects of Fermentation conditions on Bioethanol production
Utilization of sugar during fermentation is one of the important criteria in determining the production
of bioethanol. Overall trends of the effect of the optimized process of cells loading (weight of beads),
pH, temperature and fermentation time on amount of reducing sugar produced during fermentation
was presented in Figure 6.
The influence of cells loading on fermentation is studied with regards to the weight of beads. Three
different weight of beads; 3g, 6g and 9g consumed 0.041 mg/mL, 0.357 mg/mL and 1.772 mg/mL
reducing sugar respectively. Based on Figure 6, it can be seen that the amount of reducing sugars
consumed by immobilized beads with weight of 9g was the highest, followed by immobilized beads
with 6g and 3g of weight. Thus, it can be deduced that higher amount of cells loading will gave higher
yield of bioethanol. Since, higher amount of cells loading of 9g immobilized beads consumed more
sugar during fermentation process. More beads used in fermentation medium will increase the yield of
bioethanol. Similar results also obtained by Zain et al. (2011) which reported that more beads in a
solution will result in higher yield of bioethanol due to the large area for mass transfer in beads [43].
Effect of pH on amount of reducing sugar utilized during fermentation was carried out at pH 4, 5
and 6. From the results obtained (Figure 6), the highest amount of reducing sugars consumed is at pH
5 with 2.157 mg/mL. At pH 4 to 5, the amount of reducing sugar utilized during fermentation was in
an increasing trend from 1.595 mg/mL to 2.157 mg/mL. However, from pH 5 to 6, reducing sugar
consumed is drop to 1.861mg/mL at pH 6. It can be deduced that the bioethanol production will
increased until it reaches pH 5 and drops beyond pH 5. Hence, pH 5 is considered as the optimum pH
for fermentation process using banana hydrolysate. The possible reason for this is that the optimum
initial pH for the growth of yeast is about 4.5-6.0. Hence, the same range of pH in hydrolysate will
result in high efficiency of fermentation by yeast and thus giving highest yield of ethanol. Study by
Lin et al. (2012) reported that maximum bioethanol concentration is also obtained at pH 5 using
immobilised S. cerevisiae [44].
Significant influences of temperature on ethanol fermentation was investigated using three different
temperature; 30 oC, 35 oC and 40 oC. The highest amount of reducing sugar produced is at 30 oC with
1.764 mg/mL, followed by 1.274 mg/mL at 35oC and 1.241 mg/mL at 40 oC. Further increase in
fermentation temperature resulted in substantially decrease in the amount of sugar consumed as well
as the bioethanol content produced from the process. At 35 oC, the amount of reducing sugar
consumed is decreasing with an increase in temperature. The possible reason of this is that the yeast
does not grow at temperature almost 40oC and below 30°C. The temperature of fermentation can affect
the growth of S.cerevisae. Thus, it can be deduced that the optimum temperature for fermentation is at
30oC. Abdulla et al. (2018) also used temperature at 30 oC, where papaya hydrolysate was ferment
with pH 5 for 48 h led to maximum bioethanol yield of 0.5415 g/L [21]. The research by Thancharoen
(2015) showed that rotten banana waste using BRM17 yeast strain exhibited the best result for
bioethanol fermentation at 30 oC with 1.13 g/L [45].
Three different fermentation time (24, 48 and 72 h) is used in the optimization process for this
study. According to Figure 6, the amount of reducing sugars consumed is the highest at 24 h of
fermentation time with 1.737 mg/mL and then it decline after 24 h. Reducing sugar concentration at
48h and 72 h with 1.208 mg/mL and 0.893 mg/mL is lower compared to 24 h of fermentation time.
Hence, the bioethanol content will also dropped when the fermentation time is longer than 24 h. It can
be concluded that the optimum fermentation time is 24 h. Longer fermentation time causes the yeast
cell to stop converting sugar into ethanol. According to Tran et al. (2015) it is because the amount of
formed ethanol sufficient inhibits to fermenting [27]. In Jin et al. (2020), saccharification of pretreated
rice straw using crude enzyme released 22.15 g/L reducing sugars in just 20 h. Thus, resulted in an
ethanol concentration of 9.45 g/L and 83.5% bioethanol yield [46].
Hence, in order to increase the ethanol concentration after the distillation process later, the
concentration of available sugars needed to be increased so that the fermentation efficiency is also
improved [47].
Natural Disaster Seminar 2019
IOP Conf. Series: Earth and Environmental Science 1103 (2022) 012022
IOP Publishing
doi:10.1088/1755-1315/1103/1/012022
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0
0.5
1
1.5
2
2.5
2 3 4 5 6 7 8 9 10
Cells loadin g (gram)
Amo unt of r educin g sugar s consu med (mg/m l)
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
3.5 4 4.5 5 5.5 6 6.5
pH
Amo unt of r educin g sugar s consu med (mg/m l)
0.5
0.7
0.9
1.1
1.3
1.5
1.7
1.9
25 30 35 40 45
Temperat ure (°C)
Amo unt of reducin g sugar s consu med (mg/m l)
0
0.5
1
1.5
2
12 36 60 84
Time o f fermen tation (h ours)
Amo unt of r educin g sugar s consu med (mg/m l)
Figure 6. Optimized fermentation parameters, (A) cells loading, (B) pH, (C) temperature and (D)
fermentation time.
4. Conclusion
In this study, Musa acuminata Colla cv Berangan banana peels, grown in Sabah, Malaysia, was used
as a bioethanol feedstock raw material. From the experiment conducted, banana peels showed a great
potential for biofuel production. The optimized conditions for acid hydrolysis pretreatment for sugar
production is 0.10 M H2SO4, at 90oC for 20 min hydrolysis time. Then, yeast S. cerevisiae Type II
was immobilized in order to increase the yield of bioethanol. The second optimization process was
carried out in the fermentation process. At the end of the process, the optimum parameters of the
hydrolysate is 9g of cells loading (weight of beads), at 30oC, pH 5 and 24 h fermentation time. In
summary, banana peels have the potential to be used as feedstock for bioethanol production using
immobilized S. cerevisiae Type II. Further studied can be done to investigate the actual performance
of banana peels as feedstock for bioethanol production by quantifying the ethanol through a gas
chromatography analysis.
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