Chemical Composition of the Cashew Apple Bagasse and Potential Use for Ethanol Production

doi:10.4236/aces.2012.24064

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Advances in Chemical Engineering and Science, 2012, 2, 519-523

http://dx.doi.org/10.4236/aces.2012.24064 Published Online October 2012 (http://www.SciRP.org/journal/aces)

Chemical Composition of the Cashew Apple Bagasse and

Potential Use for Ethanol Production

Flávia Cristina dos Santos Lima1, Flávio Luiz Honorato da Silva2, Josivanda Palmeira Gomes3,

José Mariano da Silva Neto1

1Department of Chemical Engineering, Center of Sciences and Techn o l o gy, Federal Universi t y of C a m p i na Gran de,

Campina Grande, Brazil

2Department of Chemical Engineering, Center of Technology, Federal University of Paraiba, João Pessoa, Brazil

3Department of Agricultural Engineer in g, Center o f Science and Technology, Federal University of Campina Grande,

Campina Grande, Brazil

Email: [email protected], flavioluizh@yahoo.com.br, [email protected], [email protected]

Received August 23, 2012; revised September 25, 2012; accepted October 5, 2012

ABSTRACT

On the world scene, the energy requirements are mainly based on fossil fuels, however, these compounds reserves are

finite and their exploitation has caused serious environmental problems. As a consequence, the demand for alternative

renewable sources has been intensified in substitution the rising demand for energy and raw materials. The biomass is

emerging as one of the few sources that have potential to meet these challenges of sustainability, as is currently the

largest energy resource in the world, and only carbon-rich material available on the planet, apart from fossils. Form, the

cashew crop has great potential for technological development of alternative sources of energy, from its industrial waste

processing cashew adding value to the product. In this sense, this paper aims to study the characterization of the cashew

apple bagasse and to verify (by acid prehydrolysis) the potentia l of this material for ethanol produ ction. Initially it was

carried out physicochemical characterization of cashew bagasse used (pH, moisture content, soluble solids, sugars,

cellulose, hemicellulose and lignin). Following it was carried prehydrolysis at 105˚C for 1 h to obtain fermentable

sugars. Analyses of the samples were carried out on HPLC the results showed the saccharification of biomass with

glucose (1537.49 mg/L), xylose (3823.22 mg/L) and arabinose (7131.11 mg/L) as well as the capacity of the biomass

for ethanol production.

Keywords: Pre-Hydrolyze; Ethanol; Cashew Apple Bagasse

1. Introduction

The world’s energy needs are based on fossil fuels,

however, the impending shortage of fossil oil and envi-

ronmental problems that its holding concerned, it has

aroused in the scientific community interest in new al-

ternative energy sources renewable and sustainable [1,2].

In this context, the biomass comes as one of the sources

having this potential, because when produced sustainably,

can dramatically reduce emissions of greenhouse gases

compared to fossil fuels, as the only carbon-rich material

available on the planet [3,4], which can be used for

energy, heat, liquid and gaseous fuels, and also serves as

a raw material for chemicals and materials.

Brazil is enjoying a comfortable position in the world

with the technology of ethanol production. In this sector,

the United States is currently the largest prod ucer, except

that the bioethanol produced from corn (cost three times

higher than derived from cane sugar), followed by Brazil

which uses cane sugar, with an ethanol production of

27.7 billion liters, respectively, in the harvest of 2008/

2009 [5].

The lignocellulosic biomass represent an abundant

source of sugars by biotechnological processes can be

converted to products of industrial interest such as ethanol.

This biofuel is currently produced from virtually raw beet

and starch, cane sugar and maize, respectively. However,

researchers are developing new processes for the most

economically viable use of the component of lignocellu-

losic biomass such as agricultural residues (straw and

bagasse of sugar cane, wheat straw and corn stover) and

forest residues (dust and waste wood), for production of

fuel ethanol (second generation ethanol) [6, 7].

In Brazil, the cashew nut harvest (2008/2009) ac-

counted for 11% of world production, which represents

more than 6 million tons of cashew [8]. However, in the

Northeast, cashew agroindustry has an outstanding role

in the local economy, because, in industrial processes

40% (w/w) of bagasse is normally discarded by the in-

F. C. DOS SANTOS LIMA ET AL.

520

dustry [9]. So sustainably this culture has great potential

for technological development of alternative energy

sources, from their industrial waste processing, besides

being used as a support for cells in alcoholic fermenta-

tion of juice cashew [10].

The cashew bagasse is a lignocellulosic waste that is

composed mainly of cellulose, hemicellulose and lignin.

For these residues are bioconverted it is necessary to

subject them to physical pretreatments and/or chemicals

prior to hydro lysis in order to produce ethanol. Su ch pre-

treatment aimed at removing lignin and hemicellulose,

reducing the crystallinity of the cellulose and increasing

the porosity of these materials so as to make the pulp

more susceptible to hydrolysis. Among the various op-

tions for pre-treatment, the use of dilute acid in addition

to removing the selective hemicellulose produces li-

queurs (prehydrolysis) with high content of pentoses and

reduced lignin content [8,11].

This liquor resulting from the pre-hydrolysis is consti-

tuted by compounds such as pentoses (xylose and arabi-

nose) at high concentrations and hexoses (glucose, man-

nose, galactose, etc.) components of the hemicellulose.

During the pretreatment the acid s used as catalysts in the

process release protons that act on glycosidic bonds be-

tween the monomers polymeric sugar chains, causing the

breaking of these bonds releasing a number of undesir-

able compounds in the fermentation process, leading to

partial degradation of pentoses and hexoses, generating

furfural and 5- hydroxym et hy lfu rfural (5-HM F) [1 2].

In this context, this work was to study the characteri-

zation of the cashew apple pomace and by acid hydroly-

sis pre-determine their potential for ethanol production.

2. Materials and Methods

The investigation was conducted at the Laboratories of

Porous Media, Particulate Systems and Biochemical En-

gineering at the Chemical Engine ering Academic Unit in

the Science and Technology Center of the Universidade

Federal de Campina Grande—Paraíba state.

2.1. Obtaining a Raw Material

Fresh cashew apple bagasse was used, obtained from

FRUTNAT, a fruit juice production company located in

the city of Campina Grande/Paraiba/Brazil.

2.2. Preparation of Raw Material

The cashew apple bagasse was washed twice in water at

60˚C, and then water at room temperature until reaching

˚Brix 0. After washing, it was placed into aluminum trays

and dried in an air circulating oven at 55˚C for 48 hours,

depending (Figures 1(a)-(c)). It was then immediately

ground in a knife mill, sieved through 40 mesh sieves and

stored in polyp ropy l ene bags for subsequent use.

2.3. Acid Prehydrolysis of Cashew Apple Bagasse

Dried cashew residue was treated with a dilute acid solu-

tion (95% pure sulfuric acid—VETEC/PA), and prehy-

drolysis liquor was obtained at 105˚C for 1 h in a pres-

surized 700 mL stainless steel reactor, using a weight

ratio of 1:6 (10 0 g of sample/600 g o f H2SO4 at 3%v/v).

2.4. Characterization of Cashew Apple Bagasse:

Physicochemical Analysis

Samples of cashew bagasse dry and prehydrolysis were

taken to be its characterization, which was to analyze

(moisture, pH, soluble solids, reducing sugars, cellulose,

hemicellulose and lignin). Table 1 gives the references

of the methodologies used for physicochemical charac-

terization.

2.5. Characterization of Prehydrolysis Liquor

Levels of sugars and furan compounds (HMF and Fur-

fural) were determined by high performance liquid

chromotography (HPLC) equipped with a ProStar 210

pump (Varian); Manual injector with a 20 µL loop;

ProStar 356 refractive index detector (Varian) and 284

nm UV-visible (aldehydes); Hi-Plex H stainless steel

analytical column (300 mm × 7.7 mm; Varian), applying

the following operating conditions: Column temperature

of 40˚C; Mobile phase: 0.005 M H2SO4 with a flow rate

of 0.6 mL/min; Analysis time: 15 and 60 minutes for

(a) (b) (c)

Figure 1. Cashew apple bagasse: (a) In nature; (b) Drying

at 55˚C; (c) Dry.

Table 1. Methods used in the characterization of cashew

apple bagasse.

Parameters Analyzed Methodology

Moisture [13]

pH [13]

Soluble Solids [13]

Cellulose [14]

Lignin [14]

Hemicellulose [14]

Reducing Sugars [15]

F. C. DOS SANTOS LIMA ET AL. 521

sugar and aldehyde content, respectively. Internal stan-

dard solution for sugars: glucose, xylose, arabinose and

sucrose (Sigma 99.99% HPLC grade), congeners 5-hy-

droxymethylfurfural—HMF (Aldrich 99.98%) and fur-

fural (Vetec 99.9 UV/HPLC) were used to quantify the

component s of liquor.

3. Results and Discussion

The physicochemical characterization of cashew bagasse

dry and prehydrolyzed shown in Table 2, aims to ana-

lyze its composition with respect to nutrient content and

for future comparison with the bagasse hydrolyzate.

According to the results shown in Table 1 shows that

the analysis of dry bagasse resulted in 9.29% ± 0.07%

moisture, however, [16] analyzing the cashew stalk resi-

due dried in a vacuum oven at 65˚C found 6.99% mois-

ture. For the analysis of the pH value of 4.23 ± 0.01 was

found no significant difference with the values reported

by [16,17] at pH 4.01 and 4.52. For soluble solids was

found to be the result of 0, this is because the pulp was

well washed to remove the remaining sugar prior to dry-

ing. Now for the AR value was higher than that reported

by [18] who studied the efficiency of solvents in the ex-

tractives content in pulp of the cashew apple, finding the

dry bagasse at 55˚C the value 0.31%.

Analyzing prehydrolyzed the bagasse it is found that

the values of moisture, pH, Brix and AR found for dry

pomace cashew are similar to those found in [19] to

study the acid hydrolysis of bagasse from the stalk of the

cashew, which was reported at 14.51% moisture, pH 1.77

and 0.10% of ˚Brix.

A comparison of the chemical composition of dry ba-

gasse cashew pre-treated is shown in Table 3.

In terms of cellulose, hemicellulose and lignin, the pulp

of the cashew apple dry values were similar to that found

by [8] 19.21% ± 0.35%, 12.05% ± 0.37% and 38.11% ±

Table 2. Physicochemical characterization of the cashew

apple bagasse in natura and after pretre atment.

Parameters

analyzed Cashew

bagasse dry Bagasse of cashew

prehydrolyzed

Moisture (%) 9.29 ± 0.07 23.85 ± 0.05

pH 4.23 ± 0.01 1.70 ± 0.04

Soluble solids (˚Brix) 0.00 ± 0.00 0.00 ± 0.00

Reducing Sugars (%) 0.56 ± 0.02 1.80 ± 0.08

Table 3. Comparison between the chemical composition of

dried and crushed cashew pretreated.

Parameters analyzed Cashew

bagasse dry Bagasse of cashew

prehydrolyzed

Cellulose (%) 18.31 ± 0.07 31.50 ± 0.02

Hemicellulose (%) 27.18 ± 0.01 19.30 ± 0.09

Lignin (%) 23.91 ± 0.02 32.21 ± 0.07

0.08% for the cashew apple bagasse in nature, [20]

38.4%, 10.2% and 2.8% for soybean hulls, however, [21]

studied the same residue found 36%, 12.5% and 18.2%.

It was observed for wheat straw 31, 26 and 24%, re-

spectively [22]. The values related to lignin were higher

than those found by different authors. As can be seen the

cashew bagasse dry compared to other residues men-

tioned, appears to be quite promising for bioconversion

products of hig h a dde d val ue such as ethanol.

Bagasse from cashew stalk when subjected to pre-hy-

drolysis with dilute acid changes most of the hemicellu-

lose fraction monosaccharides by hydrolysis (xylose, ara-

binose, and others). Consequently, the pulp prehydrolyzed

has a browning in relation to the dry material due to the

formation of degradation products of carbohydrates under

acid catalysis [23] as shown in Figure 2(b). It can be seen

in Table 3 , values for cellulose, hemicellulos e and lignin.

Compared to the straw marabout 39.5%, 15.9% and 31.6%

of cellulose, hemicellulose and lignin, respectively [24]

can be observed that the amount of pulp was higher,

however, hemicell ulose and l igni n were si m il ar.

As can be seen in Table 4, the pre-hydrolysis with

dilute acid not only solubilizing hemicellulose, but also

has the power to convert it into fermentable sugars, the

resulting liquor is composed of sugars (glucose, xylose

and arabinose), making it an important residue which can

be used for producing ethanol, as shown in Figure 3 as a

percentage.

4. Conclusion

Depending on the results presented here, we can conclude

Figure 2. Peduncle of cashew bagasse (a) dry and (b)

prehydrolyzed.

Table 4. Concentration (mg/L) and sugar compounds toxic

liquor bagasse prehydrolyzed of the cashew apple.

Component Content (mg/L)

Glucose 1758.66

Xylose 5458.70

Arabinose 7640.72

Acetic acid 5.66

HMF 49.17

Furfural 0.04

F. C. DOS SANTOS LIMA ET AL.

522

Figure 3. Percentage of sugar in the liquor prehydrolyzed

bagasse peduncle of c a shew.

that the cashew bagasse biomass has great potential for

bioprocess after prehydrolysis, is a promising raw mate-

rial for bioethanol production, with 12% of hexoses, and

88% pentoses.

5. Acknowledgements

The authors would like to express thanks to Their Bra-

zilian agencies MCT/CNPq/CTBio for financial support

through the Notice MCT/CNPq/CTAgro/CTBio No. 39/

2007-Vanguard Technologies for the Production of Eth-

anol and Biod iesel (Case No. 5528 15/2007-1). CNPq for

doctoral fell o w ships and underg rad uat e r esearch.

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