Abstract Xylan and mannan are the two most abundant hemicelluloses, and
enzymes that modify these polysaccharides are prominent hemicellulases with
immense biotechnological importance. Among these enzymes, xylanases and
mannanases which play the vital role in the hydrolysis of xylan and mannan,
respectively, attracted a great deal of interest. These hemicellulases have got applications in food, feed, bioethanol, pulp and paper, chemical, and beverage producing
industries as well as in biorefineries and environmental biotechnology. The great
majority of the enzymes used in these applications are optimally active in mildly
acidic to neutral range. However, in recent years, alkaline active enzymes have also
become increasingly important. This is mainly due to some benefits of utilizing
alkaline active hemicellulases over that of neutral or acid active enzymes. One of the
advantages is that the alkaline active enzymes are most suitable to applications that
require high pH such as Kraft pulp delignification, detergent formulation, and cotton
bioscouring. The other benefit is related to the better solubility of hemicelluloses at
high pH. Since the efficiency of enzymatic hydrolysis is often positively correlated
to substrate solubility, the hydrolysis of hemicelluloses can be more efficient if
performed at high pH. High pH hydrolysis requires the use of alkaline active
enzymes. Moreover, alkaline extraction is the most common hemicellulose extraction method, and direct hydrolysis of the alkali-extracted hemicellulose could be of
great interest in the valorization of hemicellulose. Direct hydrolysis avoids the timeconsuming extensive washing, and neutralization processes required if non-alkaline
active enzymes are opted to be used. Furthermore, most alkaline active enzymes are
relatively active in a wide range of pH, and at least some of them are significantly or
even optimally active in slightly acidic to neutral pH range. Such enzymes can be
eligible for non-alkaline applications such as in feed, food, and beverage industries.
This chapter largely focuses on the most important alkaline active hemicellulases,
endo-β-1,4-xylanases and β-mannanases. It summarizes the relevant catalytic properties, structural features, as well as the real and potential applications of these
remarkable hemicellulases in textile, paper and pulp, detergent, feed, food, and
prebiotic producing industries. In addition, the chapter depicts the role of these
extremozymes in valorization of hemicelluloses to platform chemicals and alike in
biorefineries. It also reviews hemicelluloses and discusses their biotechnological
importance.
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G. Mamo
enzymes that modify these polysaccharides are prominent hemicellulases with
immense biotechnological importance. Among these enzymes, xylanases and
mannanases which play the vital role in the hydrolysis of xylan and mannan,
respectively, attracted a great deal of interest. These hemicellulases have got applications in food, feed, bioethanol, pulp and paper, chemical, and beverage producing
industries as well as in biorefineries and environmental biotechnology. The great
majority of the enzymes used in these applications are optimally active in mildly
acidic to neutral range. However, in recent years, alkaline active enzymes have also
become increasingly important. This is mainly due to some benefits of utilizing
alkaline active hemicellulases over that of neutral or acid active enzymes. One of the
advantages is that the alkaline active enzymes are most suitable to applications that
require high pH such as Kraft pulp delignification, detergent formulation, and cotton
bioscouring. The other benefit is related to the better solubility of hemicelluloses at
high pH. Since the efficiency of enzymatic hydrolysis is often positively correlated
to substrate solubility, the hydrolysis of hemicelluloses can be more efficient if
performed at high pH. High pH hydrolysis requires the use of alkaline active
enzymes. Moreover, alkaline extraction is the most common hemicellulose extraction method, and direct hydrolysis of the alkali-extracted hemicellulose could be of
great interest in the valorization of hemicellulose. Direct hydrolysis avoids the timeconsuming extensive washing, and neutralization processes required if non-alkaline
active enzymes are opted to be used. Furthermore, most alkaline active enzymes are
relatively active in a wide range of pH, and at least some of them are significantly or
even optimally active in slightly acidic to neutral pH range. Such enzymes can be
eligible for non-alkaline applications such as in feed, food, and beverage industries.
This chapter largely focuses on the most important alkaline active hemicellulases,
endo-β-1,4-xylanases and β-mannanases. It summarizes the relevant catalytic properties, structural features, as well as the real and potential applications of these
remarkable hemicellulases in textile, paper and pulp, detergent, feed, food, and
prebiotic producing industries. In addition, the chapter depicts the role of these
extremozymes in valorization of hemicelluloses to platform chemicals and alike in
biorefineries. It also reviews hemicelluloses and discusses their biotechnological
importance.
246
G. Mamo