Available online at www.buu.ac.th/BUUConference
ST-O-009
Burapha University International Conference 2015
“Moving Forward to a Prosperous and Sustainable Community”
Enhancing the Production of Reducing Sugars from Banana fruit
dietary fiber by Pretreatment Methods
Paweena Jansuk1*, Noppadon Cheamsawat2
1
King Mongkut’s University of Technology Thonburi, Multidisciplinary Collage, Chemical Engineering, Bangkok 10140, Thailand
2
King Mongkut’s University of Technology Thonburi, Faculty of Engineering, Bangkok 10140, Thailand
Abstract
The use of acid and steam explosion pretreatment to enhance reducing sugar of banana fruit dietary fiber was
investigated. Banana fruit dietary fiber obtained from production of Banana fruit syrup process. The dietary fiber in
banana fruit whose pectin and starch had been removed. The fiber was hydrolyzed with sulfuric acid (0.4% w/v) for 12
hours and was heated with saturated steam at a temperature of 200 °C for 4 minutes in a steam explosion system. The
objective of this work was to investigate the obtimal condition for pretreating Banana fruit dietary fiber with dilute
sulphuric acid and steam explosion for the production of reducing sugars. The pretreated samples reducing sugar yield
was measured after steam explosion. The result shows that acid hydrolysis using sulphuric acid at a concentration of 0.2,
0.4 and 0.6 w/v for 12 hr. gave a maximum reducing sugar yield of 1.612±0.006, 2.941±0.007 and 2.187±0.005 %(g)
respectively and steam explosion gave 6.546±0.006 %(g). In this study, steam explosion treated Banana fruit dietary fiber
prior to steam explosion had a greater capacity for hydrolyzing Banana fruit dietary fiber than dilute sulphuric acid. So
steam explosion treatment is an alternative to improve effective of reducing sugar production from banana fruit dietary
fiber.
© 2015 Published by Burapha University.
Key Words: Reducing sugar; Acid hydrolysis; Steam explosion; Banana fruit dietary fiber; Pretreatment.
*Corresponding author. Tel. +66873936221, 02-470-8326-30; fax: 02-872-8711
E-mail address: [email protected]
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Proceedings of the Burapha University International Conference 2015, 10-12 July 2015, Bangsaen, Chonburi, Thailand
1. Introduction
This research is a part of development in the main research of “Banana Innovative products”. The
projects related to this research have been developed since 2002 including 1) concentrate fructose extraction
process 2) production of RS3 contained flour from banana and 3) the development of chitosan cross-linked
dietary fiber. The fiber content of 1-3% which is 10-30 kilogram from banana 1,000 kilogram, the by-product
of the concentrate fructose extraction from banana will be in further process for supplementary food for GI
(Gastrointestinal) track system. In order to preparing banana fruit dietary fiber to bind bile acid for decrease
cholesterol in human body, the process for pretreatment in this research use 2 technic are acid hydrolysis and
steam explosion, these processes can hydrolyze dietary fiber and produce the reducing sugar. The results from
pretreatment process may be able to estimate chain length of dietary fiber too because of pretreatment with
acid hydrolysis will react at amorphous region and then dietary fiber breaks down to small pieces.
A reducing sugar is a carbohydrate that is oxidized by a weak oxidizing agent (an oxidizing agent
capable of oxidizing aldehydes but not alcohols, such as the Tollen’s reagent, Benedict's test, or the Maillard
reaction) in basic aqueous solution. The characteristic property of reducing sugars is that, in aqueous medium,
they generate one or more compounds containing an aldehyde group. eg.: α-D-glucose, which contains a
hemiacetal group and, therefore, reacts with water to give an open-chain form containing an aldehyde group.
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Proceedings of the Burapha University International Conference 2015, 10-12 July 2015, Bangsaen, Chonburi, Thailand
Torget (1990) used preteatment methods for enhancing the production of Reducing Sugars was
solution of dilute (0.4 wt.%) sulfuric acid has been also used to hydrolyze biomass, dilute acid pretreatment in
hydrolysis of hemicellulose to its monomeric units, rendering the cellulose more available. Esteghalian (1997)
used acid pretreatment and may require the use of an alkali to neutralize the hydrolysate. Addition of sulfuric
acid has been initially applied to remove hemicellulose either in combination with break down of cellulose to
glucose or prior to acid hydrolysis of cellulose. Grous (1985) removed hemicellulose by sulfuric acid and
enhanced digestibility of cellulose in the residual solids. The most widely used and tested approaches are
based on dilute sulfuric acid. Steam pretreatment is the most extensively studied and commonly applied
physicochemical method of biomass pretreatment. Macmillan (1994) used steam explosion action on the fiber
and steam explosion was previously called steam explosion because of believe that an “explosive” action on
the fiber was necessary for them to become hydrolysable. The term “autohydrolysis” has also been used as a
synonym for steam explosion describing the changes that occur during Steam explosion. Process description
and mode of action: in this process physically pretreated (chipped, ground or simply raw preconditioned)
biomass is usually treated with high pressure saturated steam at temperatures of about 160-240 °C and
pressures between 0.7 and 4.8 MPa. The pressure is held for several seconds to a few minutes to promote
hemicellulose hydrolysis and then released. Hemicellulose is the predominant fraction of the carbohydrates
solubilized in the liquid phase during pretreatment, while the lignin is transformed as result of the high
temperature. The cellulose in the solid fraction becomes more accessible hence increasing the digestibility of
the lignocellulosic feedstock. Mosier (2005) used hydrolysis process to hydrolyzed hemicellulose was thought
to be mediated by the acetic acid generated from acetyl groups associated with hemicellulose and other acids
released during pretreatment, that may further catalyse the hemicellulose hydrolysis resulting in release of
glucose and xylose monomers hence the use of the term autohydrolysis. At high severity (270 °C, 1 min)
steam explosion results in optimal hemicellulose solubilization but lower temperature and longer residence
time (190 °C, 10 min) have been shown to be more favourable because they avoid the formation of sugar
degradation products that inhibit subsequent fermentation. Mosier (2005) reported that steam explosion can be
effectively enhanced by addition of H2SO4, CO2 or SO2 as a catalyst. The use of acid catalyst increases the
recovery of hemicellulose sugars, decreases the production of inhibitory compounds and improves the
enzymatic hydrolysis on the solid residue.
The aim of the study was to obtain soluble reducing sugars by using different pretreatment methods
prior to binding bile acid properties of banana fruit dietary fiber and to determine the optimal condition of
each treatment and measure the reducing sugar produced.
2. Materials and methods
2.1. Substrate Preparation
The raw material is ripe banana fiber from the process of concentrate fructose extraction which is rinsed
by tap water filtered by carbon (non chlrine and Conductivity is not over 200 microS/cm) and digested by
α-amylase enzyme and pectinase after that cleaned by water.
2.2. Acid pretreatment by H2SO4
Each 100 grams of banana fruit dietary fiber was suspended in 250 ml 0.2, 0.4 and 0.6 w/v sulphuric acid
(H2SO4) for overnight. The solid residues were collected and washed extensively with tap water until neutral
pH was reached Dinitrosalicylic acid (DNS) Reagent.
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Proceedings of the Burapha University International Conference 2015, 10-12 July 2015, Bangsaen, Chonburi, Thailand
2.3. Steam explosion pretreatment
1,100 grams of banana fruit dietary fiber was suspended in 2500 ml 0.4 w/v H2SO4 for overnight and then
gave 14.5 kgf/cm3 pressure and heat at 200 °C for 4 min. The solid residues were collected and washed
extensively with tap water until neutral pH was reached Dinitrosalicylic acid (DNS) Reagent.
2.4. Reducing sugar assay
Add 3 ml of DNS reagent to 3 ml of sample in a lightly capped test tube. (To avoid the loss of liquid due
to evaporation, cover the test tube with a piece of paraffin film if a plain test tube is used.) Heat the mixture at
90º C for 5-15 minutes to develop the red-brown color. Add 1 ml of a 40% potassium sodium tartrate
(Rochelle salt) solution to stabilize the color. After cooling to room temperature in a cold water bath, record
the absorbance with a spectrophotometer at 575 nm.
% Fruit dietary fibre Hydrolysis = (Reducing Sugars produced by growth – Reducing sugar in control x
100)/ Reducing sugar in control
(1)
3. Results
Banana fruit dietary fiber with dilute sulphuric acid and steam explosion for the production of reducing
sugars. The pretreated samples reducing sugar yield was measured after steam explosion. The result shows
that acid hydrolysis using sulphuric acid at a concentration of 0.2, 0.4 and 0.6 w/v for 12 hr. gave a maximum
reducing sugar yield of 1.612±0.006, 2.941±0.007 and 2.187±0.005 %(g) respectively and steam explosion
gave 6.546±0.006 %(g). In this study, steam explosion treated fruit dietary fiber prior to steam explosion had
a greater capacity for hydrolyzing Banana fruit dietary fiber than dilute sulphuric acid. Shown in table1. So
steam explosion treatment is an alternative to improve effective of reducing sugar production from banana
fruit dietary fiber.
Table 1. Quantitative of Reducing Sugar
Sample
Reducing sugar (%g)
No.1
0.035±0.007
No.2
1.612±0.006
No.3
2.941±0.007
No.4
2.187±0.005
No.5
6.546±0.006
** No.1 was banana dietary fiber, No.2 was banana dietary fiber after pretreatment with acid hydrolysis
(0.2%w/v of H2SO4), No.3 was banana dietary fiber after pretreatment with acid hydrolysis (0.4%w/v of
H2SO4), No.4 was banana dietary fiber after pretreatment with acid hydrolysis (0.6%w/v of H2SO4), No.5 was
banana dietary fiber after pretreatment with steam explosion.
4. Conclusion
Experimental study to determine the appropriate method for pretreatment of banana fruit dietary fiber was
carried out using varied the concentrate of acid and steam explosion. Different pretreatment methods were
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Proceedings of the Burapha University International Conference 2015, 10-12 July 2015, Bangsaen, Chonburi, Thailand
evaluated for their ability to produce reducing sugars from banana fruit dietary fiber. Hydrolysing banana
fruit dietary fiber with steam explosion pretreatment gave a higher reducing sugar production than dilute
sulphuric acid pretreatment method. Pretreatment of banana fruit dietary fiber using 0.4 w/v H2SO4 for
overnight and then gave 14.5 kgf/cm3 pressure and heat at 200 oC for 4 minutes gave yielded % reducing
sugar of 6.546±0.006 %. So steam explosion treatment is an alternative to improve effective of reducing
sugar production from banana fruit dietary fiber.
References
Torget, R.W., Werdene, P., Grohmann, K., 1990. Dilute acid pretreatment of two short-rotation herbaceous crops, Application of
Biochem Biotech, Vol. 24/25, p. 115-126.
Esteghalian, A., Hashimoto, A.G., Fenske, J.J., Penner, M.H., 1997. Modelling and optimization of dilute sulfuric acid pretreatment of
corn stove, poplar and switchgraa. Bioresour Technol, Vol. 59, p. 129-136.
Grous, W.R., Converse, A.O., Grethlein, H.E., 1985. Effect of steam explosion pretreatment on pore size and enzymatic hydrolysis of
poplar. Enzyme and Microbial Technology, Vol. 8, p. 274-280.
McMillan, J.D., 1994. Pretreatment of lignocellulosic Biomass. Enzymatic Conversion Biomass Fuels Prod, Vol. 566. p. 292-324.
Mosier, N., Wyman, C.E., Dale, B., Elander, E.R., Lee, Y.Y., Holtzapple, M.T., 2005. Features of promising technologies for
pretreatment of lignocellulosic biomass, Bioresour Technol. Vol. 96. p. 673-686.
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