What is Lactic acid?
Do you know what type of acid is present in all the milk products including cheese, milk, curd and butter.
Yeah, absolutely it’s a Lactic acid.
Lactic acid is generally considered as an organic acid and it is produced by a fermentation process which occurs in milk sugar.
It was first identified by Carl Wilhelm in 1780 in milk. It is a colorless water-soluble substance which has been widely used in food and pharmaceuticals and it has also been synthesized by our body in many metabolic conditions.
The First Demonstration of Lactic Acid
Lactic acid was first identified by Scheele in sour milk in the year 1780. Further when Pasteur was undergoing research on pasteurization, he found the microorganism which is necessary for lactic acid production.
Lactic acid is also being commercially sold for many purposes.
How Lactic Acid is Utilized by Human Body?
Lactic acid is used for the process of conversion of glucose into energy when our body has very low oxygen content.
We often release a painful sensation when we exercise or do heavy activities suddenly or after a long interval, it is due to the accumulation of lactic acid in the muscles which results in muscle cramps at a certain area in our body.
It does not cause any serious issues as liver has the capability to breakdown the extra lactate.
How Lactic Acid Build up in Our Body?
In some cases, our muscles do not have enough oxygen to breakdown glycogen into glucose for the synthesis of energy molecules which is known as ATP, at this time lactic acid gets accumulated in a certain area where enough oxygen is not available which is often referred to as anaerobic metabolic process.
When lactate gets accumulated it leaves to formation of lactic acidosis.
It may also upgrade at the times of heart attack, sudden shock, and at the cases of lung diseases.
Lactic acid forms in many varieties at each area according to their nature.
When they are being accumulated at muscles and blood tissues they are known as dextrorotary form.
The lactate which is obtained as a result of sucrose formation is known as levorotary form, when the same lactate if produced by bacteria during fermentation they are known as racemic form.
Thus, each of its form has its origin from the process of their accumulation or synthesis.
To explain in detail about how our body produces lactic acid, as said earlier lactic acid gets accumulate in our body when we perform heavy works or exercises during a sudden period of time.
This because when we perform powerful activities, we take a long and faster breathes which leads to the usage of more oxygen by the muscles, which tend to perform that action, which results in synthesizing energy anaerobically.
We generally get energy by the process of glycolysis, where glucose is reduced to pyruvic acid and release of ATP molecules occurs through further process which is important for the energy source.
This is a general process, but when our muscles are in a state with absence or lack of oxygen the pyruvate which is produced through a process of glycolysis convert itself into a substance namely lactate and supplies energy in the anaerobic form which leads to the accumulation of lactate at higher levels.
But this is performed by our body, for a longer time it leads to side effects by the accumulation of lactate at higher levels in the tissues which also disrupts the other metabolic activities of the muscle and creates an acidic environment around the muscle cells.
So, it results in degrading a working capability of the muscle and cannot perform any heavy or powerful activities further.
But on considering an immune response of our body, natural immune barriers prevent the muscle tissues from permanent damage and initiates the cells to work normally by upcoming the situation and by performing regular muscle contraction improves the lactic acid accumulation.
This is because our body gets slow during these conditions and allows the reverse mechanism of conversion of lactate into pyruvate and normal aerobic respiration is followed by the tissues.
Fermentation of Lactic Acid
Lactic acids are also synthesized in industries for various purposes through fermentation.
Several microorganisms are involved in the production of lactic acid, each of it has the mechanism of producing either D (-) lactic acid or L (+) lactic acid depending on their nature.
The racemic form is formed due to the presence or production of an enzyme known as racemase, the lactic acid usually be in an active form unless it is deactivated by any other enzymes.
The two most important steps involved in the production of lactic acid are as follows,
1. Homo-fermentative Process
This type of process involves the utilization of certain bacteria such as Lactobacillus delbruckii, L.casei, L.leichmanii, streptococcus lactis etc. which utilizes its EMP pathway to synthesis pyruvic acid which helps in the production of lactic acid by reducing lactate dehydrogenase.
Though these microbes can serve under anaerobic conditions they are known an anaerobic microbe.
2. Heterofermentative Process
This process involves the synthesis of lactic acid, ethanol, acetic acid, carbon dioxide and water with the help of Leuconostoc mesenteroids.
Manufacturing of Lactic Acid
The medium should be prepared such that it contains masses of molasses, maltose, lactose, sucrose, calcium carbonate, hydrogen and phosphate which are kept at a pH of 5.5 to 6.5.
As lactic acid is soft and delicate in nature the mixture of metals is avoided in the culture medium and fermenters are nature based and mostly wood fermenters are used.
The use of Thermophilic clostridia in the culture results in the formation of major and important constituents of lactic acid namely butanol and butyric acid.
Uses of Lactic Acid
Considering lactic acid as a commercial one it can also be used in polymer production since it has a property of weak acid.
It is also being used in food and other industries such as production of beverages in preservation as it has an acidic property which is due to the anaerobic property of that which prevents the food from spoilage.
It is also being used in leather industries for de-lining and also in laundry and textiles for the treatment of fabric.
Calcium lactate is being used as a source of calcium in pharmaceuticals and also in baking units.
Lactic Acid Citations
- Lactic acid and exercise performance : culprit or friend? Sports Med . 2006;36(4):279-91.
- Lactic acid fermentation of human excreta for agricultural application. J Environ Manage . 2018 Jan 15;206:890-900.
- Biosynthesis of D-lactic acid from lignocellulosic biomass. Biotechnol Lett . 2018 Aug;40(8):1167-1179.