the phenolic compounds which include tyrosol, hydroxytyrosol, cinnamic acid derivatives, flavonoids, and secoiridoids. An environmentally friendly strategy namely
enzyme-assisted ultrasound hydrolysis was developed for
the isolation of antioxidant phenolic compound from olive
waste. Coffee byproduct extracts show outstanding
anti-inflammatory, anti-allergenic, and antioxidant functions
due to the existence of chlorogenic acids. The use of cellulolytic and pectinolytic enzymes improved the extraction of
lycopene from tomato peel waste by eight to 18-fold (Cho
et al. 2019). The study by Rodríguez et al. confirmed potato
waste as an excellent source of antioxidants that can successfully reduce the oxidation of oils (Rodríguez et al.
2014). Barba et al. reported a number of green approaches
for the extraction of antioxidant bioactive compounds
(especially vitamin E) from grape waste. Such innovative
approaches tend to be superior to traditional approaches in
terms of processing time and energy consumption (Barba
et al. 2016). Adinarayana et al. studied numerous substrates
such as wheat rava, wheat bran, barley bran, rice bran, corn
cob, peanut shell, and sugarcane bagasse for the synthesis of
different types of antibiotics (Adinarayana et al. 2003).
2.1.3 Pigments
Biopigments produced from microbial sources have several
advantages over synthetic pigments. Monascuspurpureus, a
fungus, produces pigments with a number of therapeutic
properties, such as cancer treatment, coronary heart disease,
and hypertension. A number of reports are accessible on the
use of FVW as a substrate for the production of carotenoids
such as kinnow peel powder and pea pod, apple pomace,
grape juice, grape must, date, sweet potato, tomato peel, and
carrot pomace. The quality of meat products can be
improved by adding lycopene and fiber-containing tomato
peel. Beetroot is known to be an important source of
water-soluble nitrogen pigments and xanthins that can help
with oxygen-induced or free radical-mediated oxidation of
biological molecules. The pigment betalain found in beetroot
is widely used as a natural colorant in the modern food
system. Dry carrot pomace can be used in 5% wheat bread
to make high-fiber biscuits, cakes, dressings, and pickles in
addition to carotenoids, fiber, and minerals and in functional
drinks. Onion pomace is used in snacks as a natural source
of high-quality functional ingredients such as dietary fiber,
primarily insoluble fractions, and in total phenols and flavonoids with high antioxidant activity (Wadhwa et al. 2015).
The high production cost of carotenoid can be reduced by
improved nutrient production using better pigment strains
(Sindhu et al. 2016).
Coffee husk and pulp have been used in the production of
flavors using the Ceratocystis fimbriata mould (Adinarayana
et al. 2003). Microbiological bioconversions of FVW into
various pigments are cost-effective compared to other synthetic approaches for the production of natural aromas.
Various microorganisms, including bacteria, yeasts, and
fungi, have been shown to be capable of producing different
aroma compounds. Vanillin is produced by bioconversion of
ferulic acid which is extracted from FVW using liquid cultures of fungi. Ferulic acid can be recovered from wheat bran
and barley spent grains using Aspergillus niger(A. niger)
(Stabnikova et al. 2010). The recent increase in the interest
in the use of coloring agents contributes to a rise in the
incidence of cancer. Cheng and Yang reported carotenoid
manufacturing using Rhodotorulamucilaginosa waste and
grape waste for the effective pigment production by
Monascuspurpureus (Sindhu et al. 2019).
2.1.4 Enzymes
Waste processing using enzymes is a newly established
stream in terms of environmental and economic aspects and
can be easily disposed of or recycled. The advantages of
using enzymes in industrial-scale productions are the processing requires minimum purification with maximum yield
and recovery of the enzymes without cell-disruption.
Biosynthesis of most proteins is controlled by cellulose
induction followed by catabolic suppression, thus permits
limiting the amount of enzyme produced in non-defined
media. Recombinant DNA techniques can be extended to the
cloning and production of industrially essential enzymes
(Gacesa and Hubble 1998).
Amylases are enzymes used to reduce starch to smaller
carbohydrate units and are an appropriate enzyme in paper,
fiber, detergent, biofuel, and milk processing. The FVW can
be used as an alternative source for the economical production of amylase. Hasan et al. reported amylase produced
by Bacillus and Chryseobacterium using FVW. Another
bacteria namely A.niger(NCIM 616)is used for the production of amylase from banana peel (Hasan et al. 2017).
Cellulases are a class of enzymes used for the complete
hydrolysis of cellulose. It has an essential role in the
hydrolysis of biomass and is used in various fields such as
biofuels, paper, textiles, detergents, and food. Julia et al.
examined the use of soya hulls using solid-state fermentation
for the production of cellulose by A.niger and found it to be
highly efficient at shorter periods that reduces the overall
process economy (Julia et al. 2016). Alkali pretreated FVW
residues are found to be a suitable substrate without an
additional supply of nutrition for improved cellulase
production.
Protease is an enzyme that catalyzes protein hydrolysis.
Applications are identified in the medical, food, and detergent industries. Ahmed et al. reported the production of
pectinase from citrus peel containing soluble carbohydrates
using A.niger (Ahmed et al. 2015). Botella et al. investigated
Potential Utilisation of Fruit and Vegetable Waste: An Overview
183
enzyme-assisted ultrasound hydrolysis was developed for
the isolation of antioxidant phenolic compound from olive
waste. Coffee byproduct extracts show outstanding
anti-inflammatory, anti-allergenic, and antioxidant functions
due to the existence of chlorogenic acids. The use of cellulolytic and pectinolytic enzymes improved the extraction of
lycopene from tomato peel waste by eight to 18-fold (Cho
et al. 2019). The study by Rodríguez et al. confirmed potato
waste as an excellent source of antioxidants that can successfully reduce the oxidation of oils (Rodríguez et al.
2014). Barba et al. reported a number of green approaches
for the extraction of antioxidant bioactive compounds
(especially vitamin E) from grape waste. Such innovative
approaches tend to be superior to traditional approaches in
terms of processing time and energy consumption (Barba
et al. 2016). Adinarayana et al. studied numerous substrates
such as wheat rava, wheat bran, barley bran, rice bran, corn
cob, peanut shell, and sugarcane bagasse for the synthesis of
different types of antibiotics (Adinarayana et al. 2003).
2.1.3 Pigments
Biopigments produced from microbial sources have several
advantages over synthetic pigments. Monascuspurpureus, a
fungus, produces pigments with a number of therapeutic
properties, such as cancer treatment, coronary heart disease,
and hypertension. A number of reports are accessible on the
use of FVW as a substrate for the production of carotenoids
such as kinnow peel powder and pea pod, apple pomace,
grape juice, grape must, date, sweet potato, tomato peel, and
carrot pomace. The quality of meat products can be
improved by adding lycopene and fiber-containing tomato
peel. Beetroot is known to be an important source of
water-soluble nitrogen pigments and xanthins that can help
with oxygen-induced or free radical-mediated oxidation of
biological molecules. The pigment betalain found in beetroot
is widely used as a natural colorant in the modern food
system. Dry carrot pomace can be used in 5% wheat bread
to make high-fiber biscuits, cakes, dressings, and pickles in
addition to carotenoids, fiber, and minerals and in functional
drinks. Onion pomace is used in snacks as a natural source
of high-quality functional ingredients such as dietary fiber,
primarily insoluble fractions, and in total phenols and flavonoids with high antioxidant activity (Wadhwa et al. 2015).
The high production cost of carotenoid can be reduced by
improved nutrient production using better pigment strains
(Sindhu et al. 2016).
Coffee husk and pulp have been used in the production of
flavors using the Ceratocystis fimbriata mould (Adinarayana
et al. 2003). Microbiological bioconversions of FVW into
various pigments are cost-effective compared to other synthetic approaches for the production of natural aromas.
Various microorganisms, including bacteria, yeasts, and
fungi, have been shown to be capable of producing different
aroma compounds. Vanillin is produced by bioconversion of
ferulic acid which is extracted from FVW using liquid cultures of fungi. Ferulic acid can be recovered from wheat bran
and barley spent grains using Aspergillus niger(A. niger)
(Stabnikova et al. 2010). The recent increase in the interest
in the use of coloring agents contributes to a rise in the
incidence of cancer. Cheng and Yang reported carotenoid
manufacturing using Rhodotorulamucilaginosa waste and
grape waste for the effective pigment production by
Monascuspurpureus (Sindhu et al. 2019).
2.1.4 Enzymes
Waste processing using enzymes is a newly established
stream in terms of environmental and economic aspects and
can be easily disposed of or recycled. The advantages of
using enzymes in industrial-scale productions are the processing requires minimum purification with maximum yield
and recovery of the enzymes without cell-disruption.
Biosynthesis of most proteins is controlled by cellulose
induction followed by catabolic suppression, thus permits
limiting the amount of enzyme produced in non-defined
media. Recombinant DNA techniques can be extended to the
cloning and production of industrially essential enzymes
(Gacesa and Hubble 1998).
Amylases are enzymes used to reduce starch to smaller
carbohydrate units and are an appropriate enzyme in paper,
fiber, detergent, biofuel, and milk processing. The FVW can
be used as an alternative source for the economical production of amylase. Hasan et al. reported amylase produced
by Bacillus and Chryseobacterium using FVW. Another
bacteria namely A.niger(NCIM 616)is used for the production of amylase from banana peel (Hasan et al. 2017).
Cellulases are a class of enzymes used for the complete
hydrolysis of cellulose. It has an essential role in the
hydrolysis of biomass and is used in various fields such as
biofuels, paper, textiles, detergents, and food. Julia et al.
examined the use of soya hulls using solid-state fermentation
for the production of cellulose by A.niger and found it to be
highly efficient at shorter periods that reduces the overall
process economy (Julia et al. 2016). Alkali pretreated FVW
residues are found to be a suitable substrate without an
additional supply of nutrition for improved cellulase
production.
Protease is an enzyme that catalyzes protein hydrolysis.
Applications are identified in the medical, food, and detergent industries. Ahmed et al. reported the production of
pectinase from citrus peel containing soluble carbohydrates
using A.niger (Ahmed et al. 2015). Botella et al. investigated
Potential Utilisation of Fruit and Vegetable Waste: An Overview
183