for its production [38]. Microbial communities like Penicillium restrictum, Aspergillus niger, Aspergillus flavus, Aspergillus wentii, Aspergillus nidulans, Aspergillus
luchensis, Acremonium sp., Trichoderma viride, Penicillium janthinellum, and
Ustulina vulgaris produce citric acid in the presence of medium that contains
inorganic salts and sugars [38]. Some species of fungi like Candida, Saccharomyces,
Hansenula, Kloekera, Torula, Pichia, Yarrowia, and Zygosaccharomyces produces
numerous amount of isocitric acid which reduces the final yield of the product.
Among various microbial sources, Aspergillus niger produces a high yield of about
112 g per 100 g of sucrose [39].
Citric acid was normally produced in industries via three methods which include
submerged, solid-state, and surface fermentation methods with the appropriate
reaction conditions like media selection, inoculum preparation, suitable nutrients
to enhance the growth of the inoculum, etc. Solid-state fermentation has been
extensively carried out in incubators, conical flasks, and bioreactors that include
both single and multilayered packed bed reactors [40]. Around 80% of citric acid
was produced using submerged fermentation technique, and industries prefer this
method due to the high productivity and low cost. Submerged fermentation could be
carried out via batch, fed-batch, and continuous method [41]. Surface fermentation
method is usually preferred by small and medium-scale industries because of its low
cost, less energy utilization, and simple installation procedure. The phenomena
occur in the fermentation chambers, and the culture is poured in the trays that got
arranged in these chambers. These chambers are controlled with proper aeration and
humidity. Both physical factors like pH, suitable aeration, and product recovery
methods like extraction, adsorption, and solvent precipitation and chemical factors
like selection of the microbial source, nutrients, and substrate selection play a major
and vital role in the citric acid production [42] is shown in Table 3.
Table 3 Agricultural residues as the feedstocks in the production of citric acid
Feedstock
Microbial
source
Method of
production
Yield
(g g
À1
)
Citric acid
production
(g L
À1
)
References
Sugarcane bagasse
and vinasse
Aspergillus
niger and
Trichoderma
reesei
Solid-state
cultivation
1.31
7.34
[43]
Sugar beet molasses and chicken
feather peptone
Aspergillus
niger
Simultaneous saccharification and
fermentation
–
68.8
[37]
Spanish style
green olive
processing
wastewater
Aspergillus
niger B60
Fermentation
0.56
85
[44]
Cassava peel
substrate
Aspergillus
niger
Submerged
fermentation
0.8
88.73
[45]
Recent Advances in Organic Acid Production from Microbial Sources by Utilizing. . .
75
luchensis, Acremonium sp., Trichoderma viride, Penicillium janthinellum, and
Ustulina vulgaris produce citric acid in the presence of medium that contains
inorganic salts and sugars [38]. Some species of fungi like Candida, Saccharomyces,
Hansenula, Kloekera, Torula, Pichia, Yarrowia, and Zygosaccharomyces produces
numerous amount of isocitric acid which reduces the final yield of the product.
Among various microbial sources, Aspergillus niger produces a high yield of about
112 g per 100 g of sucrose [39].
Citric acid was normally produced in industries via three methods which include
submerged, solid-state, and surface fermentation methods with the appropriate
reaction conditions like media selection, inoculum preparation, suitable nutrients
to enhance the growth of the inoculum, etc. Solid-state fermentation has been
extensively carried out in incubators, conical flasks, and bioreactors that include
both single and multilayered packed bed reactors [40]. Around 80% of citric acid
was produced using submerged fermentation technique, and industries prefer this
method due to the high productivity and low cost. Submerged fermentation could be
carried out via batch, fed-batch, and continuous method [41]. Surface fermentation
method is usually preferred by small and medium-scale industries because of its low
cost, less energy utilization, and simple installation procedure. The phenomena
occur in the fermentation chambers, and the culture is poured in the trays that got
arranged in these chambers. These chambers are controlled with proper aeration and
humidity. Both physical factors like pH, suitable aeration, and product recovery
methods like extraction, adsorption, and solvent precipitation and chemical factors
like selection of the microbial source, nutrients, and substrate selection play a major
and vital role in the citric acid production [42] is shown in Table 3.
Table 3 Agricultural residues as the feedstocks in the production of citric acid
Feedstock
Microbial
source
Method of
production
Yield
(g g
À1
)
Citric acid
production
(g L
À1
)
References
Sugarcane bagasse
and vinasse
Aspergillus
niger and
Trichoderma
reesei
Solid-state
cultivation
1.31
7.34
[43]
Sugar beet molasses and chicken
feather peptone
Aspergillus
niger
Simultaneous saccharification and
fermentation
–
68.8
[37]
Spanish style
green olive
processing
wastewater
Aspergillus
niger B60
Fermentation
0.56
85
[44]
Cassava peel
substrate
Aspergillus
niger
Submerged
fermentation
0.8
88.73
[45]
Recent Advances in Organic Acid Production from Microbial Sources by Utilizing. . .
75