the basis of source and structure, certain modifications can
be done to promote microbial growth for developing
desirable products of interest in an economically and environmentally benign route. A specific policy for the management of all types of FVW cannot be implemented
because of their varied composition by source (Sindhu et al.
2019). This chapter gives an overview of potential applications of bioconversion processes for the generation of energy
as well as numerous other valuable products from various
FVW.
1.1 Current Bioconversion Processes
Bioconversion methods have been developed on the basis of
the characteristics of the FVW. A number of bioconversion
processes namely fermentation, extraction, and anaerobic
digestion can be utilized for the production of biofuels,
enzymes, biopolymers, heat, electricity, etc. The current
bioconversion processes for producing valuable materials
from FVW are depicted in Fig. 1. The biochemical transformations involve anaerobic digestion and composting.
A number of processes like thermal treatments, fermentation,
or combined processes are used for the production of different industrially significant products. Thermal conversion
normally involves pyrolysis, incineration, or gasification.
Fermentation using some microorganisms is difficult due to
the FVW’s heterogeneous nature. FVW are biodegradable
and contain high moisture, and are therefore suitable for
anaerobic digestion to produce bioenergy. Such drawbacks
of FVW’s anaerobic digestion led to the reduction of pH
value during the digestion process of fatty acids. It would
prevent the development of methanogen microbes. This
challenge can be resolved by adopting integrated or alternative methods. Earlier studies have shown that focusing on
a single FVW is not profitable for bioconversion. Many
other works are being carried out around the world to turn
heterogeneous FVW into many useful products, contributing
to the creation of a viable, economical, and sustainable
approach to FVW bioconversion (Sindhu et al. 2019). To
achieve these objectives, a variety of chemical, physical,
biological, mechanical, and alternative processes have been
reported. There were numerous studies reported for the
pretreatment of FVW, including acid, alkali, ultrasound,
sequential, and surfactant-assisted pretreatments. Among
such processes, sequential pretreatment followed by alkali
treatment was observed with the highest reduction in sugar
yield. There was a generation of inhibitors in the case of acid
and alkali pretreatments. On comparing with other pretreatment methods, sequential pretreatment was considered
to be good for sugarcane bagasse to yield reduction of sugar
with better removal of lignin and hemicelluloses. The choice
of the pretreatments will be on the basis of economic
viability and the desired product. Pretreated sugarcane
bagasse is used as an effective inert support material for
microbial growth in the simultaneous saccharification and
fermentation (SSF) methods. Several pretreatment methods
have been recorded for bagasse, namely alkali, acid,
organo-solvent, organic acid, and physical treatments.
Developing a suitable pretreatment would reduce the capital
and production costs. Many industries use acid pretreatment,
and the benefit of this technique is the development of two
main processing streams namely pentose and hexose
streams. The conversion of value-added compounds is
through the pentose stream and the hexose process is utilized for bioethanol production (Sindhu et al. 2016).
1.2 Applications of Bioconversion Processes
The bioconversion of FVW into value-added products is
really attention-grabbing and has wider applications in the
medical, pharmaceutical, and allied sectors. The key
value-added products that can be derived from FVW include
enzymes, ethanol, reducing sugars, proteins, furfural,
organic acids, phenols, activated carbon, carbohydrates,
degradable plastic composites, amino acids, lipids, biosorbent, cosmetics, medicines, resins, methane, biopesticides,
fertilizer, biopromoters, surfactants, and other miscellaneous
products (Wadhwa et al. 2015). Applications of bioconversion of FVW into value-added products in various sectors
are presented in Fig. 2.
In recent years, the advent of emerging technologies for
product developments has led to a sustainable economy in
various manufacturing sectors. There are four main industrial
enzyme sectors: household, technological, food, and feed
enzymes. FVW in industry are an underutilized raw material
and is a key sector of emphasis in the global economy that
can be processed into valuable items. The use of immobilized
biocatalytic enzymes for bioconversion could improve the
ecological sustainability of production. In terms of waste
stream conditions, the absence of an appropriate immobilization system among the many available methods coupled
with specific process requirements is a significant challenge
for FVW stream valorization. Besides the differential nature
of different enzymes during immobilization, the cost poses
another major barrier to the adoption of immobilized biocatalytic waste recovery systems. Usage of processed
enzymes rather than raw extract potentially increases the
production cost. The cost of the biocatalytic immobilized
method for the recovery of FVW into commercial products
depends on the market price of raw materials and the
implementation of systematic methods for valorization.
Implementation of synthetic biological strategies that allow
site-driven immobilization enhances the stability of enzymes
in non-ideal ecosystems or leads to sub-unit stabilization.
180
R. Reshmy et al.
be done to promote microbial growth for developing
desirable products of interest in an economically and environmentally benign route. A specific policy for the management of all types of FVW cannot be implemented
because of their varied composition by source (Sindhu et al.
2019). This chapter gives an overview of potential applications of bioconversion processes for the generation of energy
as well as numerous other valuable products from various
FVW.
1.1 Current Bioconversion Processes
Bioconversion methods have been developed on the basis of
the characteristics of the FVW. A number of bioconversion
processes namely fermentation, extraction, and anaerobic
digestion can be utilized for the production of biofuels,
enzymes, biopolymers, heat, electricity, etc. The current
bioconversion processes for producing valuable materials
from FVW are depicted in Fig. 1. The biochemical transformations involve anaerobic digestion and composting.
A number of processes like thermal treatments, fermentation,
or combined processes are used for the production of different industrially significant products. Thermal conversion
normally involves pyrolysis, incineration, or gasification.
Fermentation using some microorganisms is difficult due to
the FVW’s heterogeneous nature. FVW are biodegradable
and contain high moisture, and are therefore suitable for
anaerobic digestion to produce bioenergy. Such drawbacks
of FVW’s anaerobic digestion led to the reduction of pH
value during the digestion process of fatty acids. It would
prevent the development of methanogen microbes. This
challenge can be resolved by adopting integrated or alternative methods. Earlier studies have shown that focusing on
a single FVW is not profitable for bioconversion. Many
other works are being carried out around the world to turn
heterogeneous FVW into many useful products, contributing
to the creation of a viable, economical, and sustainable
approach to FVW bioconversion (Sindhu et al. 2019). To
achieve these objectives, a variety of chemical, physical,
biological, mechanical, and alternative processes have been
reported. There were numerous studies reported for the
pretreatment of FVW, including acid, alkali, ultrasound,
sequential, and surfactant-assisted pretreatments. Among
such processes, sequential pretreatment followed by alkali
treatment was observed with the highest reduction in sugar
yield. There was a generation of inhibitors in the case of acid
and alkali pretreatments. On comparing with other pretreatment methods, sequential pretreatment was considered
to be good for sugarcane bagasse to yield reduction of sugar
with better removal of lignin and hemicelluloses. The choice
of the pretreatments will be on the basis of economic
viability and the desired product. Pretreated sugarcane
bagasse is used as an effective inert support material for
microbial growth in the simultaneous saccharification and
fermentation (SSF) methods. Several pretreatment methods
have been recorded for bagasse, namely alkali, acid,
organo-solvent, organic acid, and physical treatments.
Developing a suitable pretreatment would reduce the capital
and production costs. Many industries use acid pretreatment,
and the benefit of this technique is the development of two
main processing streams namely pentose and hexose
streams. The conversion of value-added compounds is
through the pentose stream and the hexose process is utilized for bioethanol production (Sindhu et al. 2016).
1.2 Applications of Bioconversion Processes
The bioconversion of FVW into value-added products is
really attention-grabbing and has wider applications in the
medical, pharmaceutical, and allied sectors. The key
value-added products that can be derived from FVW include
enzymes, ethanol, reducing sugars, proteins, furfural,
organic acids, phenols, activated carbon, carbohydrates,
degradable plastic composites, amino acids, lipids, biosorbent, cosmetics, medicines, resins, methane, biopesticides,
fertilizer, biopromoters, surfactants, and other miscellaneous
products (Wadhwa et al. 2015). Applications of bioconversion of FVW into value-added products in various sectors
are presented in Fig. 2.
In recent years, the advent of emerging technologies for
product developments has led to a sustainable economy in
various manufacturing sectors. There are four main industrial
enzyme sectors: household, technological, food, and feed
enzymes. FVW in industry are an underutilized raw material
and is a key sector of emphasis in the global economy that
can be processed into valuable items. The use of immobilized
biocatalytic enzymes for bioconversion could improve the
ecological sustainability of production. In terms of waste
stream conditions, the absence of an appropriate immobilization system among the many available methods coupled
with specific process requirements is a significant challenge
for FVW stream valorization. Besides the differential nature
of different enzymes during immobilization, the cost poses
another major barrier to the adoption of immobilized biocatalytic waste recovery systems. Usage of processed
enzymes rather than raw extract potentially increases the
production cost. The cost of the biocatalytic immobilized
method for the recovery of FVW into commercial products
depends on the market price of raw materials and the
implementation of systematic methods for valorization.
Implementation of synthetic biological strategies that allow
site-driven immobilization enhances the stability of enzymes
in non-ideal ecosystems or leads to sub-unit stabilization.
180
R. Reshmy et al.