presence of bioactive compounds. Processing valuable by-products from waste
material have been gained as the key interest that promotes these waste compounds
to be considered as the valuable sources [5]. Various agricultural residues such as
wheat, cereals, rice, potato, sugarcane, and beet are used as the primary substrates
due to the abundant starch content. These carbohydrate-rich feedstocks are numerously used in the food industries as well as in the industrial fermentation phenomena
and the synthesis of numerous chemical compounds [6]. Due to their easy availability and low cost, these sources are subjected under various processes like physical,
biological, and chemical methods to produce many valuable compounds. The US
department of energy has estimated that nearly 500 million tons of these agro-based
raw materials are available within the price range of nearly 20–50$/ton [7].
Various pretreatments of renewable sources for OA production are available with
the major factors that should be considered for maximal production. The enhanced
concentration level of saccharides and the physiochemical treatment of the multifarious substrates have been targeted for the concerned OA production are the key
limiting step in the practical applications. The production of intermediaries like
furfural, phenol derivatives, acetic acid, hydroxymethylfurfural, and formic acids
during the breakdown of monosaccharides inhibits the OA production [7]. The
factors like selection medium, pH maintained with the simultaneous OA accumulation, and production of various metabolites and inhibitors should also be concentrated for the maximum OA production. Though numerous raw materials act as the
source and the different microbial communities participate directly or indirectly, this
present volume of study focuses on the different agro-based substrates used in the
various organic acid productions [8, 9].
2 Organic Acids
Organic acids owing to their extensive shelf life period are used as the preservatives
and food additives that prevent the deterioration of nutrients present in them.
Normally it could be classified based on functional derivatives like monocarboxylic
and multicarboxylic acid. Based on the length of the carbon chain, they could be
classified as short-chain constitutes about 1–6 carbon atoms, medium-chain represents 7–10 carbon atoms, and long-chain fatty acids have more than 11 carbon atoms
[10]. The commercially important acids such as lactic, citric, itaconic acids, sugar
derivative acids of gluconic and ascorbic acids, play a key vital role in various
aspects of industrial applications [11], shown in Figs. 1 and 2.
2.1 Organic Acid Production
Organic acids are produced based on the aspects of biochemical pathways and
industrial pathways. Microbial sources produce based on the metabolic sequence
of the organisms which includes the glycolysis and tricarboxylic metabolic
Recent Advances in Organic Acid Production from Microbial Sources by Utilizing. . .
69
material have been gained as the key interest that promotes these waste compounds
to be considered as the valuable sources [5]. Various agricultural residues such as
wheat, cereals, rice, potato, sugarcane, and beet are used as the primary substrates
due to the abundant starch content. These carbohydrate-rich feedstocks are numerously used in the food industries as well as in the industrial fermentation phenomena
and the synthesis of numerous chemical compounds [6]. Due to their easy availability and low cost, these sources are subjected under various processes like physical,
biological, and chemical methods to produce many valuable compounds. The US
department of energy has estimated that nearly 500 million tons of these agro-based
raw materials are available within the price range of nearly 20–50$/ton [7].
Various pretreatments of renewable sources for OA production are available with
the major factors that should be considered for maximal production. The enhanced
concentration level of saccharides and the physiochemical treatment of the multifarious substrates have been targeted for the concerned OA production are the key
limiting step in the practical applications. The production of intermediaries like
furfural, phenol derivatives, acetic acid, hydroxymethylfurfural, and formic acids
during the breakdown of monosaccharides inhibits the OA production [7]. The
factors like selection medium, pH maintained with the simultaneous OA accumulation, and production of various metabolites and inhibitors should also be concentrated for the maximum OA production. Though numerous raw materials act as the
source and the different microbial communities participate directly or indirectly, this
present volume of study focuses on the different agro-based substrates used in the
various organic acid productions [8, 9].
2 Organic Acids
Organic acids owing to their extensive shelf life period are used as the preservatives
and food additives that prevent the deterioration of nutrients present in them.
Normally it could be classified based on functional derivatives like monocarboxylic
and multicarboxylic acid. Based on the length of the carbon chain, they could be
classified as short-chain constitutes about 1–6 carbon atoms, medium-chain represents 7–10 carbon atoms, and long-chain fatty acids have more than 11 carbon atoms
[10]. The commercially important acids such as lactic, citric, itaconic acids, sugar
derivative acids of gluconic and ascorbic acids, play a key vital role in various
aspects of industrial applications [11], shown in Figs. 1 and 2.
2.1 Organic Acid Production
Organic acids are produced based on the aspects of biochemical pathways and
industrial pathways. Microbial sources produce based on the metabolic sequence
of the organisms which includes the glycolysis and tricarboxylic metabolic
Recent Advances in Organic Acid Production from Microbial Sources by Utilizing. . .
69