Lactic acid (2-hydroxypropionic acid), CH3-CHOH COOH, is the most widely occurring hydroxycarboxylic acid, having a prime position due to its versatile applications in food, pharmaceutical, cosmetic, textile, leather, and chemical industries. Lactic acid was first found and described in sour milk by the Swedish chemist Karl Wilhelm Scheele (1742–1786) in 1780. It was first isolated from sour milk by CW Scheele in 1780 and was first commercially produced in 1881 by CE Avery in Littleton, MA, USA. Pasteur, Lister, and Delbruck identified lactic acid as a microbial metabolite.
Structure & Properties: Lactic acid is chiral and has two optical isomers. One is known as L-(+)-lactic acid or (S)-lactic acid a 2-Hydroxypropanoic acid (Lactic Acid)
Lactic acid is miscible with water or ethanol, and is hygroscopic. In animals, L-lactate is constantly produced from pyruvate via the enzyme Lactate Dehydrogenase (LDH) in a process of fermentation during normal metabolism and exercise. It does not increase in concentration until the rate of lactate production exceeds the rate of lactate removal, which is governed by a number of factors, including mono carboxylate transporters, concentration and isoform of LDH, and oxidative capacity of tissues. The concentration of blood lactate is usually 1–2 mmol/L at rest, but can rise to over 20 mmol/L during intense exertion.
Currently, lactic acid is becoming important as an intermediate feedstock for the production of polylactide (PLA). One of its most promising applications is in the manufacture of biodegradable and biocompatible polylactate polymers, an environmentally friendly alternative to non-biodegradable plastics derived from petrochemicals.
The carbon source for microbial production of lactic acid can be either sugar in pure form such as glucose, sucrose, lactose etc. or sugar-containing materials such as molasses, whey, sugarcane bagasse, cassava bagasse, and starchy materials from potato, tapioca, wheat, barley, and carrot. The economics of production of lactic acid and its derivatives is dependent on many factors of which the cost of raw material is very significant.
Some agricultural by-products that are potential substrates for lactic acid production are cornstarch, cassava starch, lignocelluloses/ hemicelluloses Hydrolysates, cottonseed hulls, Jerusalem artichokes, corn cob, corn stalks, beet molasses, wheat bran, rye flour, sweet sorghum, sugarcane press mud, cassava, barley starch, cellulose, carrot processing waste, molasses spent wash, corn fiber Hydrolysates, and potato starch.
Many starch-degrading LAB, Lactobacillus spp., can be also used for the one-step lactic acid production. The starch-degrading Lactobacillus spp. is L. Amylophilus, L. Amylovorus, amylolytic strains of L. Plantarum, and L. amylolyticus. Semi-solid-state fermentation is adopted in the case of certain amylolytic bacteria because they prefer to grow at higher moisture level.
Several approaches have been considered in literature for lactic acid recovery, including solvent extraction and electro dialysis. However, comparatively high amounts of solvents are needed for extraction, and toxic effects are provoked by solvents.
In the electro dialysis units, cells adhered to membranes during the process, leading to decreased efficiency in the overall recovery system. In this field, ion exchange separation provides an interesting alternative for lactic acid recovery from solutions having low concentration and complex composition, as in the case of fermentation media.
There are several issues that need to be addressed for the biotechnological production of lactic acid, such as the development of high-performance lactic acid-producing microorganisms and the lowering of the costs of raw materials and fermentation processes.
LACTIC ACID PROCESS
Fermentation of Glucose based on Corn (or) Soybean (or) Potato with the help of Lactobacillus strain produces crude lactic Acid. Crude lactic Acid is then neutralized to Calcium Lactate by using Calcium Carbonate. Crude salt is regenerate by acidification and recovered by filtration, which is further concentrated, decolorized and demonized to meet the quality specifications of pure Lactic Acid
APPLICATIONS OF LACTIC ACID & ITS SALTS
a) In sugar confectionary, it is use in continuous production line for high boiled sweets to make perfectly clear sweets with minimum sugar inversion and with no air trapped.
b) In bakery products it is used for direct acidification of bread. It increases butter stability and volume.
c) To produce a mild and pleasant taste to acid pickles, relishes and salad dressings. Lactic acid suppresses Coli form and Mesenteric group of Bacteria. Also used in Jams, Jellies, and Frozen fruit desserts.
d) In Dairy Products such as cottage cheese, addition of lactic acid is preferred to fermentation. Also used in imitation Dairy products such as cheese and yoghurt powder.
e) Lactic acid is widely used in preserving fruits like firmness of Apple slices during processing and it also inhabitant’s discoloration of fruits and some vegetables.
f) Use of buffered lactic acid improves the taste and flavor of many beverages, such as soft drinks, mineral water, carbonated fruit juices etc.
g) In breweries lactic acid is used for pre- adjustments during the mashing process and during wart cooking acidification with lactic acid of lager beer improves the microbial stability and as well as flavor.
h) It also used in processing of meal in sauces for canned fish, to improve the taste and flavors and to relieve the unpleasant amine flavor from fish meal for incorporation into bread.
i) Lactic acid is used as pH regulator for Pharma products.
j) It is suitable as a starting material in the synthesis of chiral products e.g. herbicides or pharmaceuticals. It is also used as monomer for poly lactates, a new generation of Bio Degradable polymers.
k) It is in many decalcification products such as cleaners for Toilets, Bathrooms and coffee machines. It possesses anti microbial properties.
l) Lactic acid is used in Nickel plating processes because of its unique complexion constant for nickel. It simultaneously acts as pH Buffer and stabilizer for broth.
It is the preferred choice in preparation for calcium deficiency therapy, since it is a calcium salt with high solubility and bio-availability.
It is an excellent calcium source in tablet making by pharma industry. Besides the powdered form, granular forms are also available for the direct compression of calcium lactate into tablets.
Calcium Lactate is used to fortify milk and fermented dairy drinks.
Calcium Lactate enriches products such as sport and health drinks, fruit juices, diet foods and infant formulas and improves bio-availability.
It is used as anti-tartar agent in many oral care products such as toothpaste and mouthwash.
1. In the pharmaceutical (Human Medication) industry
Calcium is an essential element of tissues and blood which contains approximately 10 milligram per 100 milliliters. The average daily requirement of calcium is 500 milligrams, but larger amounts are necessary for periods of growth, pregnancy and lactation. Inadequate calcium absorption leads to rickets and imperfect calcification of bones and teeth.
The demand by the infant through the mother during pregnancy and during lactation may cause deflection of calcium from the maternal bones. The deficiency is more often caused by lack of vitamin D. Therefore; calcium preparations for this purpose usually contain both calcium and vitamin D.
The main therapeutic classes are
- Calcium Therapy
- Multi –vitamins
- Sedatives and hypnotics
- Calcium Gluconate has significant advantages over other calcium salts
- Law toxicity
- Better palatability better texture
- Higher stability
- Low astringency
2. in the Veterinary Pharmaceutical Industry
Here Calcium Lactate is used for the treatment of hypocalcaemia in cases of milk fever. Calcium Lactate is the product of choice for such treatments, because it has no irritating effect on the body tissue. In order to increase the solubility it is mixed with boric acid. In cases of grass tentany the product is used in combination with Magnesium Lactate
3. in the Food Industry
Frequently, Calcium Lactate is added to food for its nutrition / health value e.g. in baby fruit, juices, biscuits, health foods etc. Another use in the incorporation of Calcium Lactate in instant pudding powder mixes in order to increase the speed of reaction. Although Calcium Lactate is more expensive than some other Calcium salts, it has the preference for quality products. It does not give the pudding a sour taste since it is neutral.