90
and shifting the pH of the medium to acidic (5.0 ± 6.5) or alkaline (8.0 ± 9.0) will
decrease the production of pectinases for almost 50%. A study by Khatri et al.
(2015) showed that pectinase was active at a temperature between 30 °C and 70 °C
and pH (6.2–9.2). The optimum temperature and pH were confirmed at 50 °C and
8.2, respectively. In addition to that, the thermostable and alkaline pectinase was
stable up to 70 ° C and about 82% of the enzyme was still active at 100 ° C. Okinji
et al. (2019) reported a purified 4.45-fold of pectinase obtained from Aspergillus
fumigatus, isolated from soil with a recovery of 26.16% with molecular weight of
31.6 kDa. The purified enzyme showed high activity at 60 °C with optimum pH of
5.0 being stable with temperature range between 40 and 50 °C.
Fungal pectinases should remain purified for the characterization of its properties. Pectinases from a wide range of microorganisms have been purified by several
researchers (Table 6.2). According to Contreas and Voget (2004), about 470-fold of
the PGI was successfully purified with a recovery of 8.6% from a crude sample of
Aspergillus kawachii. The purification was done using acetone, precipitation, followed by Sepharose Q and Sephacryl S-100 column chromatography. Different
types of microorganisms, pectinase enzyme production, and purification method are
presented in Table 6.2.
6.2.3 Chemical Structure and Sources of Pectic Substance
Pectin substances are complex with high molecular mass glycosidic macromolecules comprised of the structure of homogalacturonan (HG), rhamnogalacturonan I
(RG-I), rhamnogalacturonan II (RG-II), and xylogalacturonan (XGA).
Homogalactron (HG) is the simplest form of pectin because it is a linear polymer
composed of 1,4-linked α-D-galacturonic acid (GalA) residue (Martens-uzunova
and Schaap 2009; Pedrolli et al. 2009). However, pectin have been also found in
other polymer form composed of HG and RGI part with side chain composed of
neutral sugars (Voragen et al. 1995; Pedrolli et al. 2009). Although the structure of
rhamnogalacturonan II (RG-II) is less abundant, it is the most complex form of
pectin structure compared to rhamnogalacturonan I (RG-I). According to Zakharova
et al. (2018), the pectin structure is built from a backbone of rhamnogalacturonan I
(RG-I) as this structure is the most common form where α-L-rhamnose of the
hydroxyl groups of C2 and C1 is inside the polygalacturonic acid chain and linked
to the C1 and C4 of the different ends of polygalacturonic acid chain. From the
linked C4 of the α-L-rhamnose, the side chains can be varied which are galactran,
arabinan, or arabinogalactans I and II. Furthermore, for some elongation or extension of the side chain, the monomer of L-rhamnose will form and are called hairy
regions, whereas for some less elongation or extension of the side chain with
L-rhamnose, they are called smooth regions. However, the other references from
Richard and Hilditch (2009) stated that in pectin, the monomer of D-galacturonic
H. Suhaimi et al.
and shifting the pH of the medium to acidic (5.0 ± 6.5) or alkaline (8.0 ± 9.0) will
decrease the production of pectinases for almost 50%. A study by Khatri et al.
(2015) showed that pectinase was active at a temperature between 30 °C and 70 °C
and pH (6.2–9.2). The optimum temperature and pH were confirmed at 50 °C and
8.2, respectively. In addition to that, the thermostable and alkaline pectinase was
stable up to 70 ° C and about 82% of the enzyme was still active at 100 ° C. Okinji
et al. (2019) reported a purified 4.45-fold of pectinase obtained from Aspergillus
fumigatus, isolated from soil with a recovery of 26.16% with molecular weight of
31.6 kDa. The purified enzyme showed high activity at 60 °C with optimum pH of
5.0 being stable with temperature range between 40 and 50 °C.
Fungal pectinases should remain purified for the characterization of its properties. Pectinases from a wide range of microorganisms have been purified by several
researchers (Table 6.2). According to Contreas and Voget (2004), about 470-fold of
the PGI was successfully purified with a recovery of 8.6% from a crude sample of
Aspergillus kawachii. The purification was done using acetone, precipitation, followed by Sepharose Q and Sephacryl S-100 column chromatography. Different
types of microorganisms, pectinase enzyme production, and purification method are
presented in Table 6.2.
6.2.3 Chemical Structure and Sources of Pectic Substance
Pectin substances are complex with high molecular mass glycosidic macromolecules comprised of the structure of homogalacturonan (HG), rhamnogalacturonan I
(RG-I), rhamnogalacturonan II (RG-II), and xylogalacturonan (XGA).
Homogalactron (HG) is the simplest form of pectin because it is a linear polymer
composed of 1,4-linked α-D-galacturonic acid (GalA) residue (Martens-uzunova
and Schaap 2009; Pedrolli et al. 2009). However, pectin have been also found in
other polymer form composed of HG and RGI part with side chain composed of
neutral sugars (Voragen et al. 1995; Pedrolli et al. 2009). Although the structure of
rhamnogalacturonan II (RG-II) is less abundant, it is the most complex form of
pectin structure compared to rhamnogalacturonan I (RG-I). According to Zakharova
et al. (2018), the pectin structure is built from a backbone of rhamnogalacturonan I
(RG-I) as this structure is the most common form where α-L-rhamnose of the
hydroxyl groups of C2 and C1 is inside the polygalacturonic acid chain and linked
to the C1 and C4 of the different ends of polygalacturonic acid chain. From the
linked C4 of the α-L-rhamnose, the side chains can be varied which are galactran,
arabinan, or arabinogalactans I and II. Furthermore, for some elongation or extension of the side chain, the monomer of L-rhamnose will form and are called hairy
regions, whereas for some less elongation or extension of the side chain with
L-rhamnose, they are called smooth regions. However, the other references from
Richard and Hilditch (2009) stated that in pectin, the monomer of D-galacturonic
H. Suhaimi et al.