Comparing biosorbent ability of modified citrus and durian rind pectin
Wong Weng Wai, Abbas F.M. AlKarkhi, Azhar Mat Easa
*
School of Industrial Technology, 11800 USM, Minden, Penang, Malaysia
article info
Article history:
Received 16 October 2008
Received in revised form 9 September 2009
Accepted 11 September 2009
Available online 18 September 2009
Keywords:
Biosorbents
Heavy metals
Modified durian rind pectin
Modified citrus pectin
MANOVA
Cluster analysis
abstract
Biosorbent ability of modified durian rind, durian rind, citrus and modified citrus pectin for removals of
toxic heavy metals was investigated, and data were analyzed using multivariate analysis of variance
(MANOVA) and cluster analysis (CA). Degree of esterification (% DE) of the biosorbents ranged between
22.33% and 60.81%, and was in the order; modified citrus pectin < modified durian rind pectin < durian
rind pectin < citrus pectin. In most cases the order of biosorbent ability was; modified citrus pec-
tin > modified durian rind pectin, citrus pectin > durian rind pectin. MANOVA showed a significant differ-
ence between samples and concentration of biosorbents, while CA classified the four biosorbent samples
(based on biosorbent ability) into three different clusters; (1) citrus pectin and modified durian rind pec-
tin, (2) durian rind pectin and (3) modified citrus pectin. The uptake of heavy metal by biosorbents was
dependent on chemical structure of pectin and increased with biosorbent concentration and in most
cases in accordance with the reduction in % DE.
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
Heavy metals are dangerous because they tend to undergo a
process of bioaccumulation. Their potential toxic effects accumu-
late within sensitive organs and tissues. For humans, poisoning
by most of these metals causes severe dysfunction of kidney,
reproductive system, liver, brain and central nervous system
(Manahan, 1994).
Pectin are the ionic plant polysaccharides, which main struc-
tural features are the linear chains containing more than 100
(1–4)-linked
a
-
D
-galacturonic acid residue (Schols & Voragen,
1996). Pectin is typically used as a gelling agent in certain food
products. As the ability to form gels of pectin depends on the
molecular size and degree of esterification (DE), it is expected
that pectin of different sources to have different gelling ability.
At present commercial pectins are almost exclusively derived
from citrus peel or apple pomace, both by-products from juice
industries. Apple pomace contains 10–15% of pectin on a dry mat-
ter basis, while citrus peel contains 20–30%. One potential use of
pectin is as a biosorbent. Heavy metal binding ability of pectin
has been reported by Khotimchenko, Kovalev, and Khotimchenko
(2007) and Kartel, Kupchik, and Veisov (1999). Modified citrus
pectin or MCP is a complex polysaccharide obtained from the peel
and pulp of citrus fruits. It is produced from citrus pectin via pH
and temperature modification that breaks it into shorter, non-
branched, galactose-rich carbohydrate chains. These shorter
chains dissolve more readily in water and are better absorbed
and utilized by the body than the long-chain pectin. Heavy metal
removal ability of modified citrus pectin in human blood stream
has been demonstrated by Eliaz and Rode (2003). Other than
the heavy metal removal ability, modified citrus pectin also has
a binding affinity for galectins on the surface of cancer cells,
resulting in an inhibition, or blocking of cancer cell aggregation,
adhesion and metastasis (Raz & Loton, 1987). It can be envisaged
that a conversion of conventional pectin into its modified coun-
terparts promises greater return in investment.
Durian (Durio zibethinus) is one of the famous fruit commodities
in Malaysia and some other South East Asia countries. The edible
portion of the fruit, known as the aril only accounts for about
15–30% of the mass of the entire fruit (Brown, 1997). During the
season of durian, the amounts of the rind disposition as waste
could lead to environmental problems. Water soluble polysaccha-
rides that had been extracted from durian rind contain a high
amount of pectin (Hokputsa et al., 2004) that could be further uti-
lized for industrial uses. At pH 3 and in the presence of 65% sugar,
durian rind pectin formed strong gels (Easa, 2005) suggesting the
suitability of the product as a gelling agent. However the use of
durian rind pectin and modified durian rind pectin as a biosorbents
has never been studied. Such an evaluation is expected to enhance
the value of pectin from durian rind waste.
The objective of this study was to compare biosorbent ability of
modified durian rind pectin with durian rind pectin, citrus pectin
and modified citrus pectin. Modification of durian rind pectin is
expected to change the carboxyl residues in pectin and would
affect the biosorbent ability of the modified products. The biosor-
bent abilities of the pectin samples will be statistically analyzed
using multivariate statistical analysis.
0144-8617/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carbpol.2009.09.018
* Corresponding author. Tel.: +60 4 6533888x2222; fax: +60 4 6573678.
E-mail address: azhar@usm.my (A.M. Easa).
Carbohydrate Polymers 79 (2010) 584–589
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Carbohydrate Polymers
journal homepage: www.elsevier.com/locate/carbpol