The yield of lactic acid also depends on the derivative of sugar that has been used
as the source of carbon in the productive metabolic pathways. Though the genetically engineered strains such as Lactobacillus plantarum ΔldhL1-xpk1::tkt and
Enterococcus mundtii QU25 produce lactic acid from pentose sugar derivative
through homolactic acid fermentation, the yield was comparatively low, and also
the concentration of pentose sugar was also affected due to the metabolic flux created
by the above microbial sources [28]. When xylose was selected, as the carbon
source, the yield of production was high in comparison with the other sugar
derivatives [29] is shown in Table 2.
4 Citric Acid
Citric acid or 2-hydroxy-1,2,3-propane tricarboxylic acid has been extensively used
in the wide industrial applications of food, cosmetics, pharmaceutical, beverage, and
nutraceutical products since they found to be the emulsifier, acidulant, preservative,
and buffering agent [35]. Citric acid is widely found in fruits, animals, and plants
such that it plays a prominent role in the biochemical pathways that were explained
in the Krebs cycle [36]. Citric acid is the excellent cross-linking agent when it gets
dissolved with glycerol where it shows the enhanced thermal degradable property
with stable mechanical properties in starch films [37].
4.1 Production of Citric Acid
Citric acid was initially produced as the commercial source from Aspergillus niger
and later chemicals like glycerol and 1,3 dichloroacetone act as the primary substrate
Table 2 Agricultural residues as the feedstocks in the production of lactic acid
Feedstock
Microbial source
Method of
production
Yield
(g g
À1
)
Lactic acid
production
(g L
À1
)
References
Wheat straw Bacillus coagulans
MA-13
Saccharification
and Fermentation
1.23
1.11
[30]
Rice straw
slurry
Lactobacillus
plantarum
Simultaneous Saccharification and
Fermentation
0.35
1.0
[31]
Orange peel
waste
hydrolysates
Lactobacillus
delbrueckii
Fermentation
0.86
2.02
[32]
Dairy
products
Enterococcus hirae
Fermentation
0.89
13.9
[33]
Sugarcane
molasses
Clostridium sensu
stricto, Escherichia,
Enterococcus
Fermentation
0.81
112.34
[34]
74
D. Vishnu et al.
as the source of carbon in the productive metabolic pathways. Though the genetically engineered strains such as Lactobacillus plantarum ΔldhL1-xpk1::tkt and
Enterococcus mundtii QU25 produce lactic acid from pentose sugar derivative
through homolactic acid fermentation, the yield was comparatively low, and also
the concentration of pentose sugar was also affected due to the metabolic flux created
by the above microbial sources [28]. When xylose was selected, as the carbon
source, the yield of production was high in comparison with the other sugar
derivatives [29] is shown in Table 2.
4 Citric Acid
Citric acid or 2-hydroxy-1,2,3-propane tricarboxylic acid has been extensively used
in the wide industrial applications of food, cosmetics, pharmaceutical, beverage, and
nutraceutical products since they found to be the emulsifier, acidulant, preservative,
and buffering agent [35]. Citric acid is widely found in fruits, animals, and plants
such that it plays a prominent role in the biochemical pathways that were explained
in the Krebs cycle [36]. Citric acid is the excellent cross-linking agent when it gets
dissolved with glycerol where it shows the enhanced thermal degradable property
with stable mechanical properties in starch films [37].
4.1 Production of Citric Acid
Citric acid was initially produced as the commercial source from Aspergillus niger
and later chemicals like glycerol and 1,3 dichloroacetone act as the primary substrate
Table 2 Agricultural residues as the feedstocks in the production of lactic acid
Feedstock
Microbial source
Method of
production
Yield
(g g
À1
)
Lactic acid
production
(g L
À1
)
References
Wheat straw Bacillus coagulans
MA-13
Saccharification
and Fermentation
1.23
1.11
[30]
Rice straw
slurry
Lactobacillus
plantarum
Simultaneous Saccharification and
Fermentation
0.35
1.0
[31]
Orange peel
waste
hydrolysates
Lactobacillus
delbrueckii
Fermentation
0.86
2.02
[32]
Dairy
products
Enterococcus hirae
Fermentation
0.89
13.9
[33]
Sugarcane
molasses
Clostridium sensu
stricto, Escherichia,
Enterococcus
Fermentation
0.81
112.34
[34]
74
D. Vishnu et al.