LWT - Food Science and Technology 44 (2011) 62e66
Contents lists available at ScienceDirect
LWT - Food Science and Technology
journal homepage: www.elsevier.com/locate/lwt
Process optimization for aqueous extraction of reducing sugar from cashew apple
bagasse: A potential, low cost substrate
Arindam Kuila, Anshu Singh, Mainak Mukhopadhyay, Rintu Banerjee*
Microbial Biotechnology and Downstream Processing Laboratory, Agricultural and Food Engineering Department, Indian Institute of Technology, Kharagpur 721 302, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 9 December 2009
Received in revised form
30 March 2010
Accepted 3 June 2010
The present investigation deals with optimization of aqueous extraction of reducing sugar from cashew
apple bagaase, a potential low cost substrate. Response Surface Methodology (RSM) based Box Behnken
Design (BBD) was employed to obtain the best possible combination of liquid: solid, pH, extraction time
and extraction temperature for maximum reducing sugar extraction. The optimum extraction conditions
were as follows: liquid: solid 3.26 (mL/g), pH 6.42, extraction time 6.30 h and temperature 52.27 C.
Under these conditions, the experimental yield was 56.89 (g/100 g dry substrate), which was well
matched with the predictive yield 57.64 (g/100 g dry substrate). Further analysis of sugar was done by
HPLC which revealed glucose (34.28 g/100 g dry substrate), fructose (18.57 g/100 g dry substrate) and
arabinose (3.42 g/100 g dry substrate).
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
Cashew apple bagasse
Response surface methodology
Aqueous reducing sugar extraction
HPLC analysis
1. Introduction
Cashew nut tree (Anacardium occidentale L.) is a branchy evergreen tree. It has several important medicinal applications. The
receptacle is used against sore throat. Anacardol and anacardic acid
(oils from this plant) have activity against Walker carsinosarcoma.
The true fruit of the tree is the cashew nut consisting of edible
kidney-shaped kernel. The cashew apple and nut abscise from trees
naturally when ripe. Maturation occurs over a period of several
weeks during the dry season. According to the report of Pinheiro,
Rocha, Macedo, and Goncalves (2008) India is the third most
producer (4 million tons) of the worldwide production (2 billion
tons). An interesting feature of the cashew is that the nut develops
first and when it is full-grown but not yet ripe, its peduncle
becomes pulpy, fleshy, pear-shaped, so-called cashew apple. In
addition to the valuable cashew nut, the cashew nut tree is source
of byproduct i.e. pseudo fruit (cashew apple) that is used to make
juices and wines (Da Silva, Collares, & Finzer, 2000). According to
the report of Tigressa, Gustavo, and Luciana (2008) only 12 g/100 g
of the total peduncle, the part of the tree that connects it to the
cashew nut, is processed. Also, when the pseudo fruit is industrially
processed for the production of juice, 40 g/100 g of the fruit remains
as bagasse (Tigressa et al., 2008). This bagasse is not used for human
consumption and is generally stored or discarded. But due to large
* Corresponding author. Tel.: þ91 3222 283104; fax: þ91 3222 282244.
E-mail address: [email protected] (R. Banerjee).
0023-6438/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.lwt.2010.06.005
surface area and high sugar/moisture content makes bagasse
difficult for preservation. The utilization of this biomass requires
development and optimization of technologies for the industrialization of cashew apple derivatives, among which extraction of
reducing sugar before spoilage should be of particular interest.
Those facts, together with its rich in sugar content turn cashew
apple bagasse into different valuable products such as ethanol (Liu,
Cheng, Jhang, Li, & Wang, 2009), additives (Denner, 1990) etc, thus
attract increasing interests. The key issue for utilization of cashew
apple bagasse is extraction of reducing sugar from it. There are
several reports on production of reducing sugar from agro residues,
food wastes, lignocellulosic biomass and so on (Gong, Chen, & Chen,
1996; Hernández-Salas et al., 2009; Morjanoff, Dunn, & Gray, 1982;
Raghavendra & Geeta, 2007; Rocha, Rodrigues, Macedo, &
Gonçalves, 2009; Rodríguez-Chong, Alberto Ramírez, Garrote, &
Vázquez, 2004). Limitations of all these processes, such as physical or chemical pretreatment require special instrument and
consume a lot of energy. They often lead to the losses of carbohydrates and generate some inhibitors to the subsequent enzymatic
hydrolysis during the severity of the operational condition. It
makes the process uneconomical and environmental unfriendliness (Yu, Zhang, He, Liu, & Yu, 2009). Enzymatic process requires
high cost enzyme and also enzymatic process is much slower
(Taherzadeh & Korimi, 2007). Extraction of reducing sugar by
varying liquid: solid, pH, incubation time and temperature (without
any enzymatic, physical or chemical treatment) offers several
advantages such as no enzyme requirements, higher yields,
minimal byproduct formation, the absence of substrate loss due to
A. Kuila et al. / LWT - Food Science and Technology 44 (2011) 62e66
Table 1
Biochemical composition of cashew apple bagasse.
Constituents
Content (g/100 g substrate)
Moisture
Ash
Volatile matter
Reducing sugar
Starch
Cellulose
58.00
1.07
32.04
7.25
4.28
14.25
chemical modifications, low energy requirements, mild operating
conditions, low chemical disposal costs etc (O’Dwyer, Zhu, Granda,
& Holtzapple, 2007; Tunga et al., 1999).
In order to the effective utilization of bagaase, extraction of
bimolecule (reducing sugar) can be one of the options. The present
study aimed at optimization of aqueous extraction of reducing sugar
from cashew apple bagaase by varying liquid: solid (mL/g), pH,
incubation time (h) and temperature ( C). In this study RSM
(Bhattacharya & Banerjee, 2008; Mundra, Desai, & Lele, 2007) based
on BBD (Bhattacharya, Karmakar, & Banerjee, 2009) was used to
optimize the extraction of reducing sugar from cashew apple bagasse.
2. Materials and methods
2.1. Materials
Cashew apple was collected locally from the agricultural farm at
IIT Kharagpur, India.
2.2. Methods
2.2.1. Preparation of substrate
Cashew apples were sorted and weighed. Known weights of the
fresh apples were fed into the Twister mixer grinder (Bajaj, India).
Table 2
Experimental design (conditions and responses) for aqueous extraction of reducing
sugar from cashew apple bagasse, in terms of coded factor.
Run order
A
B
C
D
Reducing sugar
(g/100 g of dry substrate)
Experimental
Predicted
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
þ1(5)
þ1(5)
0(3)
0(3)
0(3)
þ1(5)
1(1)
0(3)
0(3)
1(1)
0(3)
0(3)
þ1(5)
1(1)
0(3)
0(3)
1(1)
0(3)
þ1(5)
0(3)
1(1)
0(3)
þ1(5)
0(3)
0(3)
1(1)
0(3)
0(6)
þ1(8)
0(6)
0(6)
þ1(8)
0(6)
1(4)
1(4)
1(4)
0(6)
þ1(8)
0(6)
1(4)
0(6)
0(6)
1(4)
0(6)
e 1(4)
0(6)
þ1(8)
þ1(8)
þ1(8)
0(6)
0(6)
0(6)
0(6)
0(6)
0(6)
0(6)
1(4)
0(6)
0(6)
1(4)
0(6)
0(6)
þ1(8)
þ1(8)
0(6)
0(6)
0(6)
1(4)
þ1(8)
0(6)
0(6)
e1(4)
0(6)
1(4)
0(6)
þ1(8)
þ1(8)
1(4)
0(6)
0(6)
þ1(8)
1(40)
0(50)
1(40)
0(50)
1(40)
0(50)
0(50)
1(40)
0(50)
0(50)
þ1(60)
0(50)
0(50)
0(50)
1(40)
þ1(60)
þ1(60)
0(50)
þ1(60)
0(50)
0(50)
0(50)
0(50)
þ1(60)
0(50)
1(40)
þ1(60)
32.43
38.40
30.89
56.45
40.12
38.78
24.54
28.45
47.31
27.09
45.80
57.82
35.70
31.22
42.89
34.78
39.05
41.07
45.98
45.09
35.67
52.01
40.55
43.73
54.95
33.04
46.02
31.58
39.81
33.53
56.41
39.77
36.79
25.39
31.90
40.88
34.10
47.37
56.41
36.48
32.87
42.57
40.15
32.63
37.04
43.27
44.24
37.15
48.76
43.92
46.31
56.41
28.47
45.64
63
Table 3
Results of regression analysis of aqueous extraction of reducing sugar from cashew
apple bagasse using second-order polynomial model.
Model term
Regression coefficient
Std. deviation
t-statistic
P-value
Intercept
A
B
C
D
AA
BB
CC
DD
AB
AC
AD
BC
BD
CD
382.81
18.59
27.45
22.95
9.56
3.44
1.99
1.43
0.09
0.53
0.37
0.09
0.04
0.01
0.12
92.12
8.44
9.51
9.51
2.33
0.52
0.52
0.52
0.02
0.60
0.60
0.12
0.60
0.12
0.12
4.16
2.20
2.89
2.41
4.10
6.66
3.85
2.78
4.20
0.88
0.62
0.79
0.07
0.07
1.02
0.001
0.048
0.014
0.033
0.001
0.000
0.002
0.017
0.001
0.394
0.548
0.445
0.944
0.947
0.329
The model is having 3 jars, 3 blades and power consumption of
750 W. Water was added into the mixer grinder in the ratio of 2
(mL/g of cashew apple) and then blending was done. After the juice
extraction, the remaining solid residue (bagaase) was air dried
overnight at 37 C.
2.2.2. Determination of biochemical compositions of cashew apple
bagasse
Using some methods (Erol, Haykiri-Acma, & Küçükbayrak, 2009;
Miller, 1959; Updegraff, 1969; Viles & Silverman, 1949) major
biochemical composition (moisture, ash, starch, reducing sugar and
cellulose) of cashew apple bagasse was determined in triplicates.
Table 1 shows the major biochemical composition of cashew apple
bagasse.
2.2.3. Aqueous extraction of reducing sugar from cashew apple
bagasse
Aqueous extraction of reducing sugar was performed in 50 ml
stoppered conical flask containing air dried cashew apple bagasse
and 10 ml of 0.2 (mol/L) of disodium hydrogen phosphate/0.1 (mol/
L) of citrate buffer (pH 4e8). Samples were taken from the reaction
mixture at specific time interval according to the experimental
design. Each sample taken from the reaction mixture was centrifuged at 136.4 g force for 5 min. Then reducing sugars (g/100 g
dry cashew apple bagasse) in the supernatant was estimated by
dinitrosalicylic acid method (Miller, 1959).
2.2.4. Optimization of aqueous extraction of reducing sugar from
cashew apple bagasse
For optimization of reducing sugar extraction from cashew
apple bagasse the boundary parameters were liquid: solid (1e5),
Table 4
ANOVA analysis of RSM model for aqueous extraction of reducing sugar from cashew
apple bagasse.
Source
Regression
Linear
Square
Interaction
Residual error
Lack-of-fit
Pure error
Total
R2 ¼ 86.58%,
a
b
c
DFa
Seq SSb
Adj SSb
Adj MSc
F
P
14
4
4
6
12
10
2
27
R2 ¼ 70.93%
1762.33
553.01
1144.84
64.47
273.05
268.93
4.12
2035.38
1762.33
470.62
1144.84
64.47
273.05
268.93
4.12
125.88
117.65
286.21
10.75
22.75
26.89
2.06
5.53
5.17
12.58
0.47
0.003
0.012
0.000
0.816
13.05
0.073
Degrees of freedom.
Sum of squares.
Mean squares.
64
A. Kuila et al. / LWT - Food Science and Technology 44 (2011) 62e66
sample. It consisted of an isocratic elution mobile phase of acetonitrileewater (75: 25, mL/mL), degassed before use. The flow-rate
of the eluent was 1.8 ml/min at 25 C column temperature. The
injected volume was 20 ml at a run time of 15 min. Sugar standards
were used for quantification of different sugars (glucose, xylose,
mannose, galactose, arabinose etc) in the sample.
3. Result and discussion
3.1. Biochemical composition analysis of cashew apple bagasse
Fig. 1. Response surface plot showing the effect of liquid: solid (v/dw) and pH on
aqueous extraction of reducing sugar.
pH (4e8), incubation time (4e8 h) and temperature (40 Ce60 C).
Table 2 shows the coded and actual values of the experimental
variables.
In the present work, RSM based on BBD was used to investigate
the significance of the effects of liquid to solid ratio (mL/g), pH,
incubation time (h) and temperature ( C) on extraction of reducing
sugar from cashew apple bagasse. All experiments were conducted
in triplicates. A three-level, four-factor factorial BBD and at the
center points leading to 27 runs (24 organized in a fractional
factorial design and 3 involving replications of the central points)
was developed by MINITAB 15 software for the optimization. The
series of experiments designed and conducted are shown in Table 2
in coded and uncoded terms. In coded terms the lowest, central and
the highest levels of four variables are 1, 0 and þ1 respectively.
The experimental data were analyzed by the Response Surface
Regression (RSREG) procedure to fit the following second-order
polynomial equation (Zheng et al., 2008):
Y ¼ ßk0 þ
4
X
i¼1
ßki xi þ
4
X
i¼1
ßkii x2i þ
4
4
X
X
ßkij xi xj
i ¼ 1 j ¼ iþ1
where Y is response (g of reducing sugar/100 g dry substrate); bk0,
bki, bkii and bkij are constant coefficients and xi, xj are the coded
independent variables, which influence the response variables Y.
2.2.5. Analysis of reducing sugars through HPLC
After optimization of reducing sugar extraction, an HPLC system
was used for analysis of sugars present in the optimized aqueous
Biochemical compositions of cashew apple bagasse are shown in
Table 1. Reducing sugar and cellulose content are differ from Rocha
et al. (2009) and Tigressa et al. (2008) respectively. The variation
may be due to the influence of different factors on cashew apple
cultivation and cashew apple juice extraction. Table 1 also shows
that cashew apple bagasse contain 4.28 (g/100 g substrate) starch
and 32.04 ((g/100 g substrate) volatile matter.
3.2. Statistical analysis of the data
The experimental data were first analyzed in order to determine
second-order equations including terms of interaction between the
experimental variables. The equation given below is based on the
statistical analysis of the experimental data shown in Table 2. The
mathematical expression of relationship of reducing sugar yield
from cashew apple bagasse with variables A, B, C and D (liquid:
solid, pH, incubation time and temperature respectively) are given
below in terms of coded factors.
Y ¼ 382:81 þ 18:59A þ 27:45B þ 22:95C þ 9:56D
3:44 A2 1:99B2 1:43C 2 0:09D2 0:53AB þ 0:3AC
þ 0:09AD þ 0:04BC 0:08BD1 0:12CD
(1)
Based on the experimental response the reducing sugar yield
increased from 7.25 to 57.82 g/100 g dry substrate. Runs 7 and 12
had the minimum and maximum reducing sugar extraction
respectively. The quadratic regression model for reducing sugar
yield has been given in Table 3. ANOVA of the regression model
(Table 4) for reducing sugar yield demonstrated that the model was
significant due to F-value (5.53) and R2 value (0.87). Only 13% of the
total variations are not explained by the model and the F value
indicates that reducing sugar extraction from cashew apple bagasse
had a good model fit due to the high value of R2 and F. The p values
are used as a tool to check the significance of each coefficient,
which also indicates that the interaction strength between each
Fig. 2. Response surface plot showing the effect of liquid: solid (v/dw) and incubation time (h) on aqueous extraction of reducing sugar.
A. Kuila et al. / LWT - Food Science and Technology 44 (2011) 62e66
65
Fig. 3. Response surface plot showing the effect of pH and incubation time (h) on aqueous extraction of reducing sugar.
independent variable. The smaller the p values, the bigger the
significant of the corresponding coefficient (Cui et al., 2006)
3.3. Effect of liquid: solid, pH and incubation time on aqueous
extraction of reducing sugar
The combined effect of liquid: solid and pH has been demonstrated in Fig. 1. Reducing sugar production was increased with the
increasing liquid: solid, but after specific liquid: solid 3.26 (mL/g)
increasing the liquid: solid decreased the reducing sugar production. Increasing the pH significantly increased the reducing sugar
yield. Liquid: solid with pH significantly impact on extraction of
reducing sugar.
The joint interaction of liquid: solid and incubation time on
reducing sugar yield was revealed in Fig. 2. Increasing incubation
time (h) also increased the reducing sugar production with liquid:
solid due to incubation time optimum. The maximum reducing
sugar produced (56.89 g/100 g dry substrate) at specific liquid: solid
3.26 (mL/g) and incubation time (6.3 h).
In Fig. 3 it was observed that increasing incubation time with
the pH reducing sugar production was increased significantly, but
at specific pH (6.42) and incubation time (6.30 h) reducing sugar
production was maximum (56.89 g/100 g dry substrate). Further
increasing the pH reducing sugar production was slowly decreased.
3.4. Optimization of aqueous extraction of reducing sugar from
cashew apple bagasse
The optimal conditions for aqueous extraction of reducing sugar
from cashew apple bagasse were estimated by Minitab 15 software.
Taking costs and efficiency into consideration, the optimum operating parameters was liquid: solid 3.26 (mL/g), pH 6.42, incubation
time 6.30 h and temperature 52.27 C. Under these conditions, the
maximum reducing sugar produced was about 57.64 g/100 g dry
substrate. To confirm the predicted response, using theoretical
optimum response experiments were conducted in triplicates. The
maximum reducing sugar production was found to be 56.89 g/100 g
dry substrate. This is very close to the predicted response. Thus
optimization of aqueous extraction of reducing sugar from cashew
apple bagasse was successfully developed by RSM. Enzymatic
saccharification of alkali pretreated cashew apple bagasse for 72 h,
produced 730 mg/g alkali pretreated cashew apple bagasse (Rocha
et al., 2009). Choudhury, Gray, and Dunn (1980) reported that using
Cellulomonas strain CS1-17 on alkali pretreated sugarcane bagasse
produced 25.6 g/l reducing sugar after 48 h incubation time
(Choudhury et al., 1980). Similarly Woiciechowski, Nitsche, Pandey,
and Soccol (2002) carried out experiment on production of
reducing sugar using acid hydrolysis of cassava bagasse which
resulted 62.40 g reducing sugar/g of cassava bagasse
(Woiciechowski et al., 2002). All the methods of pretreatment has
prospective to release fermentable sugars. But extraction of
reducing sugar by varying liquid: solid, pH, incubation time and
temperature is efficient and has numerous advantages. Thus,
aqueous extraction of reducing sugar is more effective in obtaining
the reducing sugars, which could be the source of useful products.
3.5. HPLC analysis of reducing sugar
After optimization of aqueous extraction of reducing sugar from
cashew apple bagasse, HPLC-RI detection was used to analyze the
sugars present in the optimized samples. Glucose and fructose
showed acceptable recoveries (34.28 g/100 g dry substrate and
18.57 g/100 g dry substrate respectively). Besides these sugars the
optimized sample contains arabinose (3.42 g/100 g dry substrate).
Damasceno, Fernandes, Magalhães, and Brito (2008) determined
sugars in the cashew apple juice. Cashew apple juice contains
glucose, fructose and sucrose, but no arabinose was found.
4. Conclusion
Biochemical analysis of cashew apple bagasse showed that it
contains moisture 58.00 g/100 g substrate, ash 1.07 g/100 g substrate,
volatile matter 32.04 g/100 g substrate, reducing sugar 7.25 g/100 g
substrate, starch 4.28 g/100 g substrate and cellulose 14.25 g/100 g
substrate. Statistical optimization of reducing sugar extraction was
successfully carried out using RSM based on the 24 factorial BBD. The
optimum conditions for reducing sugar extraction were determined
as follows: liquid: solid 3.26 (mL/g), pH 6.42, incubation time 6.30 h
and temperature 52.27 C. Under these optimum conditions the
experimental results reducing sugar yield was 56.89 (g/100 g dry
substrate). An HPLC system was used to analyze the sugars present in
the optimized sample. The aqueous sample contains glucose (34.28 g/
100 g dry substrate), fructose (18.57 g/100 g dry substrate) and
arabinose (3.42 g/100 g dry substrate).
References
Bhattacharya, S. S., & Banerjee, R. (2008). Laccase mediated biodegradation of 2,4dichlorophenol using response surface methodology. Chemosphere, 73(1),
81e85.
Bhattacharya, S. S., Karmakar, S., & Banerjee, R. (2009). Optimization of laccase
mediated biodegradation of 2,4-dichlorophenol using genetic algorithm. Water
Research, 43(14), 3503e3510.
Choudhury, N., Gray, P. P., & Dunn, N. W. (1980). Reducing sugar accumulation from
alkali pretreated sugar cane bagasse using cellulomonas. Applied Microbiology
and Biotechnology, 11, 50e54.
Cui, F. J., Li, F., Xu, Z. H., Xu, H. Y., Sun, K., & Tao, W. Y. (2006). Optimization of the
medium composition for the production of mycelial biomass and exo-polymer
66
A. Kuila et al. / LWT - Food Science and Technology 44 (2011) 62e66
by Grifola frondosa GF 9801 using response surface methodology. Bioresource
Technology, 97, 1209e1216.
Da Silva, K. D. P., Collares, F. P., & Finzer, J. R. D. (2000). A simple and rapid method
for estimating the content of solids in industrialized cashew juice. Food
Chemistry, 70, 247e250.
Damasceno, L. F., Fernandes, F. A. N., Magalhães, M. M. A., & Brito, E. S. (2008). Nonenzymatic browning in clarified cashew apple juice during thermal treatment:
kinetics and process control. Food Chemistry, 106, 172e179.
Denner, W. H. B. (1990). Food additives: recommendations for harmonization and
control. Food Control, 1(3), 150e162.
Erol, M., Haykiri-Acma, H., & Küçükbayrak, S. (2009). Calorific value estimation of
biomass from their proximate analyses data. Renewable Energy, 35, 170e173.
Gong, C. S., Chen, C. S., & Chen, L. F. (1996). Pretreatment of sugar cane bagasse
hemicellulose hydrolysate for ethanol production by yeast. Applied Biochemistry
and Biotechnology, 57e58, 49e56.
Hernández-Salas, J. M., Villa-Ramírez, M. S., Veloz-Rendón, J. S., RiveraHernández, K. N., González-César, R. A., Plascencia-Espinosa, M. A., et al. (2009).
Comparative hydrolysis and fermentation of sugarcane and agave bagasse.
Bioresource Technology, 100, 1238e1245.
Liu, Q., Cheng, K. K., Jhang, J. A., Li, J. P., & Wang, G. H. (2009). Statistical optimization
of recycled-paper enzymatic hydrolysis for simultaneous saccharification and
fermentation via central composite design. Applied Biochemistry and Biotechnology. doi:10.1007/s12010-008-8446-2.
Miller, G. L. (1959). Use of dinitrosalicylic acid reagent for determination of reducing
sugar. Analytical Chemistry, 31, 426e428.
Morjanoff, P., Dunn, N. W., & Gray, P. P. (1982). Improved enzymatic digestibility of
sugar cane bagasse following high temperature autohydrolysis. Biotechnology
Letters, 4, 187e192.
Mundra, P., Desai, K., & Lele, S. S. (2007). Application of response surface methodology to cell immobilization for the production of palatinose. Bioresource
Technology, 98, 2892e2896.
O’Dwyer, J. P., Zhu, L., Granda, C. B., & Holtzapple, M. T. (2007). Enzymatic hydrolysis
of lime pretreated corn stover and investigation of the HCH-1 model: inhibition
pattern, degree of inhibition, validity of simplified HCH-1 model. Bioresource
Technology, 98(16), 2969e2977.
Pinheiro, A. D. T., Rocha, M. V. P., Macedo, G. R., & Goncalves, L. R. B. (2008). Evaluation of cashew apple juice for the production of fuel ethanol. Applied
Biochemistry and Biotechnology, 148, 227e234.
Raghavendra, B. H., & Geeta, G. S. (2007). Pre-treatment of agroresidues for release
of maximum reducing sugar. Karnataka Journal of Agricultural Science, 20,
771e772.
Rocha, M. V. P., Rodrigues, T. H. S., Macedo, G. R. D., & Gonçalves, L. R. B. (2009).
Enzymatic hydrolysis and fermentation of pretreated cashew apple bagasse
with alkali and diluted sulfuric acid for bioethanol production. Applied
Biochemistry and Biotechnology, 155, 104e114.
Rodríguez-Chong, A., Alberto Ramírez, J., Garrote, G., & Vázquez, M. (2004).
Hydrolysis of sugar cane bagasse using nitric acid: a kinetic assessment. Journal
of Food Engineering, 61, 143e152.
Taherzadeh, M. J., & Korimi, K. (2007). Enzyme based hydrolysis processes for
ethanol from lignocellulosic materials: a review. Bioresources, 2, 707e738.
Tigressa, H. S. R., Gustavo, A. S. P., & Luciana, R. B. G. (2008). Effects of inoculum
concentration, temperature and carbon sources on tannase production during
solid state fermentation of cashew apple bagasse. Biotechnology and Bioprocess
Engineering, 13, 571e576.
Tunga, R., Banerjee, R., & Bhattacharya, B. C. (1999). Some studies on optimization of
extraction process for protease production in SSF. Bioprocess Engineering, 6,
485e489.
Updegraff, D. M. (1969). Semimicro determination of cellulose in biological materials. Analytical Biochemistry, 32(3), 420e424.
Viles, F. J., Jr., & Silverman, L. (1949). Determination of starch and cellulose with
anthrone. Analytical Chemistry, 21, 950e953.
Woiciechowski, A. L., Nitsche, S., Pandey, A., & Soccol, C. R. (2002). Acid and enzymatic hydrolysis to recover reducing sugars from cassava bagasse: an economic
study. Brazilian Archives of Biology and Technology, 45, 393e400.
Yu, J., Zhang, J., He, J., Liu, Z., & Yu, Z. (2009). Combinations of mild physical or
chemical pretreatment with biological pretreatment for enzymatic hydrolysis
of rice hull. Bioresource Technology, 100, 903e908.
Zheng, Z. M., Hu, Q. L., Jian, H., Feng, X., Guo, N. N., Yan, S., et al. (2008). Statistical
optimization of culture conditions for 1, 3-propanediol by Klebsiella pneumoniae AC 15 via central composite design. Bioresource Technology, 99, 1052e1056.