11.1 Introduction
The tremendous wringing and discharge of fossil fuels have insistently diminished
its innate resources and consequently provoked serious hazards to living world
(Sajith et al. 2016). Thus, accelerated interest pertaining to environmental deterioration and the reduction of fossil fuels urges to use substitute sustainable energy
reserves in order to counter the consistently growing energy consumptions
(Dashtban et al. 2009). Currently, the notion of waste-to-energy became the central
spotlight of numerous industries with a commercial aspect and feasible processes
manifesting the utilisation of biomass accordingly (Kendry 2002). As long as plants
have thrived, deposits from greenery have been substantial donors to the ecosystem
of our planet. Cellulose forms the skeletal constituent of the basic structure of the
green plants especially their cell coverings, that is, many forms of the oomycetes
together with algae. Biofilms are produced by some species of bacteria through
secretion of cellulose (Lekh Ram et al. 2014). Cellulose is the fibrous, insoluble,
crystalline homopolymer constructed with glucose units cemented by glycosidic
bonds of β-1,4-linkage (Jagtap and Rao 2005). From the point of energy content,
cellulose is considered as the low-priced energy source in addition to the most
bountiful sustainable biological reserve (Lynd et al. 2008; Zhang et al. 2009;
Coral et al. 2002). Cellulose has drawn worldwide attention as it can be transformed
into bioenergy and bio-based products. In recent times, due to the sky-touching price
of the employment process, stupendous quantities of municipal, agricultural and
industrial cellulosic leftovers are being utilised slovenly (Kim et al. 2003).
Cellulose is being preowned by the society since way back, but its capability as a
storage house of energy was captured posterior to the perception of the of cellulases
(Bhat and Bhat 1997). It is exploited as a nutrient stock by a variety of microbial
groups inclusive of bacteria, fungi, plants and protests as well as invertebrate animals
such as nematodes, crustaceans, insects, molluscs and annelids (Watanabe and
Tokuda 2001; Davidson and Blaxter 2005). The aforementioned microbes employ
a battery of enzymes called cellulase sequentially to support the breakdown of
cellulose to simple form of energy like glucose (Beguin and Aubert 1994).
Free monosaccharide is released from cellulose being acted upon by cellulases
through hydrolysis for the generation of bioethanol and various synthetic products as
well, a few of which serves as future alternatives for liquid fuel by-products (Bozell
and Petersen 2010). However, mechanisms of cellulose breakdown by cellulase
enzymes were partially disclosed, owing to the raised degree of crystallinity and
less water solubility of cellulose fibres (Yamada et al. 2005). To date, the towering
challenges of the past decades remain to persist, that is, the exploration of costeffective enzyme-based conversion of complex carbohydrate (cellulose) to
monosaccharides. The three major disputes are (1) the current requisite for lengthy
duration of operations to achieve an elevated cellulase release, (2) the feedback
inhibition by glucose and by-products released during cellulase development, and
(3) the growth associated complications at an elevated concentration of cellulose
from the point of liquid kinetic impulsions.
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The tremendous wringing and discharge of fossil fuels have insistently diminished
its innate resources and consequently provoked serious hazards to living world
(Sajith et al. 2016). Thus, accelerated interest pertaining to environmental deterioration and the reduction of fossil fuels urges to use substitute sustainable energy
reserves in order to counter the consistently growing energy consumptions
(Dashtban et al. 2009). Currently, the notion of waste-to-energy became the central
spotlight of numerous industries with a commercial aspect and feasible processes
manifesting the utilisation of biomass accordingly (Kendry 2002). As long as plants
have thrived, deposits from greenery have been substantial donors to the ecosystem
of our planet. Cellulose forms the skeletal constituent of the basic structure of the
green plants especially their cell coverings, that is, many forms of the oomycetes
together with algae. Biofilms are produced by some species of bacteria through
secretion of cellulose (Lekh Ram et al. 2014). Cellulose is the fibrous, insoluble,
crystalline homopolymer constructed with glucose units cemented by glycosidic
bonds of β-1,4-linkage (Jagtap and Rao 2005). From the point of energy content,
cellulose is considered as the low-priced energy source in addition to the most
bountiful sustainable biological reserve (Lynd et al. 2008; Zhang et al. 2009;
Coral et al. 2002). Cellulose has drawn worldwide attention as it can be transformed
into bioenergy and bio-based products. In recent times, due to the sky-touching price
of the employment process, stupendous quantities of municipal, agricultural and
industrial cellulosic leftovers are being utilised slovenly (Kim et al. 2003).
Cellulose is being preowned by the society since way back, but its capability as a
storage house of energy was captured posterior to the perception of the of cellulases
(Bhat and Bhat 1997). It is exploited as a nutrient stock by a variety of microbial
groups inclusive of bacteria, fungi, plants and protests as well as invertebrate animals
such as nematodes, crustaceans, insects, molluscs and annelids (Watanabe and
Tokuda 2001; Davidson and Blaxter 2005). The aforementioned microbes employ
a battery of enzymes called cellulase sequentially to support the breakdown of
cellulose to simple form of energy like glucose (Beguin and Aubert 1994).
Free monosaccharide is released from cellulose being acted upon by cellulases
through hydrolysis for the generation of bioethanol and various synthetic products as
well, a few of which serves as future alternatives for liquid fuel by-products (Bozell
and Petersen 2010). However, mechanisms of cellulose breakdown by cellulase
enzymes were partially disclosed, owing to the raised degree of crystallinity and
less water solubility of cellulose fibres (Yamada et al. 2005). To date, the towering
challenges of the past decades remain to persist, that is, the exploration of costeffective enzyme-based conversion of complex carbohydrate (cellulose) to
monosaccharides. The three major disputes are (1) the current requisite for lengthy
duration of operations to achieve an elevated cellulase release, (2) the feedback
inhibition by glucose and by-products released during cellulase development, and
(3) the growth associated complications at an elevated concentration of cellulose
from the point of liquid kinetic impulsions.
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S. Akula and N. Golla