101
at 120 min of incubation time, 50 °C of incubation temperature, and 0.05 mg/100
gm of enzymatic concentration can give the maximum yield of 96.8% for plum
fruits (Sharma et al. 2017). PGase from fungi has optimum activity at 50 °C, while
from yeast the temperature varies from 40 °C to 60 °C (Sandri et al. 2011).
6.3.6.3 Effect of Metal Ion
The production of microbial enzymes is also affected by metal ions. Studies reported
that the presence of Cu
2+
and Hg
+
greatly reduces the activity of endo PGase. Metal
ions such as Hg
2+
, Zn
2+
, and Mg
2+
inhibit enzyme production due to inhibition by
thiol group blocking agents as there is possible involvement of the thiol group in the
enzyme’s active site (Kaur et al. 2010; Guo et al. 2019). The presence of Mn
2+
could
increase the PGase activity. However, Li
+
, Fe
2+
, and Rb
2+
have no effect on the activity. At high concentration of metal ions, the enzyme production is low due to blockage of secretion of protein into external medium. Bacterial pectate lyases need Ca
2+
for growth, whereas fungal pectinase does not need Ca
2+
(Sandri et al. 2011; Sharma
et al. 2017).
6.3.7 Pectin as an Inducer
Microbial systems enhance pectinolytic production using pectin as an inducer. The
main chain of pectin is methylated 1,4-D-galacturonan molecule. Demethylated
pectin is known as pectic acid or polygalacturonic acid. Pectic substances are classified into four main types: pectic acids, pectinic acid, protopectin, and pectin.
Pectic acid is a group designation applied to pectic substances mostly composed of
colloidal polygalacturonic acids and essentially free from methoxy groups. The
salts of pectic acid are either normal or acid pectates. The pectinic acids contain up
to 75% methylated galacturonate units. Under suitable conditions, pectinic acids are
capable of forming gels with sugars and acid or, if suitably low in methoxyl content,
with certain metallic ions. The salts of pectinic acid are either normal or acid pectinates. Protopectin is the water-insoluble parent pectic substance, located primarily
in the middle lamella that serves as the glue to hold cells together in the cell walls.
It yields pectin or pectinic acids upon restricted hydrolysis.
Pectic substances are commonly amorphous, with a degree of polymerization of
about 200–400. Substituents can be found at the C-2 or C-3 positions of the main
chain. Substituents can be either non-sugar (acetyl) or sugar (D-galactose, D-xylose,
L-arabinose, and L-rhamnose). The degree and type of branching varies depending
on the source of the pectic substance. The synthesis of pectic substances occurs in
the Golgi apparatus from UDP-D-galacturonic acid during the early stages of
growth in young enlarging cell walls. Lignified tissues have very lower pectin content compared with young and actively growing tissues. Higher plants usually have
very low pectic content, especially less than 1%. Vegetables and fruits are abundant
6 Fungal Pectinases: Production and Applications in Food Industries
at 120 min of incubation time, 50 °C of incubation temperature, and 0.05 mg/100
gm of enzymatic concentration can give the maximum yield of 96.8% for plum
fruits (Sharma et al. 2017). PGase from fungi has optimum activity at 50 °C, while
from yeast the temperature varies from 40 °C to 60 °C (Sandri et al. 2011).
6.3.6.3 Effect of Metal Ion
The production of microbial enzymes is also affected by metal ions. Studies reported
that the presence of Cu
2+
and Hg
+
greatly reduces the activity of endo PGase. Metal
ions such as Hg
2+
, Zn
2+
, and Mg
2+
inhibit enzyme production due to inhibition by
thiol group blocking agents as there is possible involvement of the thiol group in the
enzyme’s active site (Kaur et al. 2010; Guo et al. 2019). The presence of Mn
2+
could
increase the PGase activity. However, Li
+
, Fe
2+
, and Rb
2+
have no effect on the activity. At high concentration of metal ions, the enzyme production is low due to blockage of secretion of protein into external medium. Bacterial pectate lyases need Ca
2+
for growth, whereas fungal pectinase does not need Ca
2+
(Sandri et al. 2011; Sharma
et al. 2017).
6.3.7 Pectin as an Inducer
Microbial systems enhance pectinolytic production using pectin as an inducer. The
main chain of pectin is methylated 1,4-D-galacturonan molecule. Demethylated
pectin is known as pectic acid or polygalacturonic acid. Pectic substances are classified into four main types: pectic acids, pectinic acid, protopectin, and pectin.
Pectic acid is a group designation applied to pectic substances mostly composed of
colloidal polygalacturonic acids and essentially free from methoxy groups. The
salts of pectic acid are either normal or acid pectates. The pectinic acids contain up
to 75% methylated galacturonate units. Under suitable conditions, pectinic acids are
capable of forming gels with sugars and acid or, if suitably low in methoxyl content,
with certain metallic ions. The salts of pectinic acid are either normal or acid pectinates. Protopectin is the water-insoluble parent pectic substance, located primarily
in the middle lamella that serves as the glue to hold cells together in the cell walls.
It yields pectin or pectinic acids upon restricted hydrolysis.
Pectic substances are commonly amorphous, with a degree of polymerization of
about 200–400. Substituents can be found at the C-2 or C-3 positions of the main
chain. Substituents can be either non-sugar (acetyl) or sugar (D-galactose, D-xylose,
L-arabinose, and L-rhamnose). The degree and type of branching varies depending
on the source of the pectic substance. The synthesis of pectic substances occurs in
the Golgi apparatus from UDP-D-galacturonic acid during the early stages of
growth in young enlarging cell walls. Lignified tissues have very lower pectin content compared with young and actively growing tissues. Higher plants usually have
very low pectic content, especially less than 1%. Vegetables and fruits are abundant
6 Fungal Pectinases: Production and Applications in Food Industries