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                      '        PRODUCTION OF LACTIC ACID THROUGH FERMENTATION TECHNOLOGY'
                      
lactic acid is one of the most commercially useful Hydroxycarboxylic acid  It has  varied range of applications not only in industry but in homes as well.

Microorganism such as bacteria and fungi are used in the production of lactic acid from the given raw materials like agricultural wastes, cellulosic materials etc.

Naturally lactic acid is produced in the muscle sells and the red blood cells of the human body. It is formed when the body breakdowns the carbohydrates to use as energy when the oxygen levels re low i.e during anaerobic conditions.

=== INTRODUCTION===='

lactic acid is of earnest importance as it is not only used as raw material for various food products by fermentation , but is also used in pharmaceutical and textile industry. Besides its application in the food preservation, textile industry ,pharmaceutical industry ,it is also used as a flavouring agent, acidulant and inhibitor of bacteria. Its water retaining capacity makes it useful as a moisturiser in the cosmetic formulations. Due to the presence of carboxyl and hydroxyl in its structure, it can be converted into useful chemicals like esters, bio solvents .etc. There are various fermentation methods of lactic acid which include continuous batch fermentations, fed-batch and batch.

==== RAW MATERIALS ====

cheap raw materials are required to produce lactic acid by fermentation at low cost. The raw materials should also have properties  such as ability to produce high yield ,negligible formation of by product.
the following are some chap raw material used for the fermentation process: starchy materials such as corn. potato, rice and wheat starch and cellulosic materials such as wood. cellulose  are mainly used as raw material as they are easily available.
cellulosic material have beta (1,4) glucan, lignin, arabinan, galactan and xylan.
Apart from starchy and cellulosic materials , renewable sources such as agricultural residues that have carbohydrates in them .whey and molasses which are common agricultural byproducts and are considered as wastes can also be used in  the production of lactic acid.

=== MICROORGANISMS FOR LACTIC ACID PRODUCTION ===

Lactic acid microorganisms can be classified as bacteria , fungi and yeast. Most commonly used microorganism is bacteria. Bacteria is preferred over fungus because the production rate of fungal fermentation is low due to mass transfer limitations.

BACTERIA

lactic acid producing bacteria are classified into 4 main categories which are called as lactic acid bacteria (LAB), Escherichia coli, Corneybacterium glutamicum, Bacillus strains. the strain has to be chosen very carefully because factors such as yield , productivity , purity and nutrition are dependent on it.LAB can produce lactic acid by anaerobic glycolysis with high yield and productivity. In general , the optimal pH range for growth of bacteria is 3.5 -9.6 and the optimal temperature is 5- 45 degree celcius.

FUNGI

Fungal species used in the production of lactic acid is Rhizopus. some advantages of fungal fermentation over bacterial fermentation include low cost downstream process, low nutrient requirements , and formation of fungal biomass, which is an important by product. The main drawback of lactic acid fermentation by fungus is that the lactic yield is reduced as carbon is utilised for the production of by -products.

YEASTS

the major advantages of using yeast as nutrient source include their tolerance against low pH (1.5), which prevents the regeneration of precipitated calcium lactate .

FERMENTATION METHODS FOR LACTIC ACID PRODUCTION

the three methods of fermentation are practised, namely, batch fermentation, fed-batch fermentation and continuous fermentation.

BATCH FERMENTATION

In this process , all the required materials such as carbon source , nitrogen and other components are added prior to beginning of the fermentation process. the most common advantage of this process is that it prevents contamination to a good extent, as it is a closed system, and so high concentrations of lactic acid is produced. in separate hydrolysis and fermentation process , the raw materials are first pre treated and the unnecessary compounds, such as lignin are eliminated . Then the raw materials are subjected to enzymatic saccharification and the hydrolysate is subjected to fermentation.

FED-BATCH FERMENTATION

in this process , all the required raw materials such carbon , nitrogen source and all the other components are added during the fermentation process at different. This type of fermentation is especially useful to maintain low substrate concentration by supplying nutrients to fermentation culture which in turn reduces substrate inhibition.

CONTINUOUS FERMENTATION

it involves addition of fresh medium to the fermenter while withdrawing the already existing broth at the same rate, this maintains the concentration of substrates and products .Few drawbacks of this process is that :contamination, requirement of field operator with expertise and also it is expensive.

===== BIOCHEMISTRY=====

there are 3processes: 1. HOMOFERMENTATIVE PROCESS: glucose + 2ADP +2 Pi = 2 lactase + 2ATP

2. HETEROFERMENTATIVE PROCESS: glucose +ADP +Pi =lactase + ethanol+ CO2 bacteria involved- Lactobacillus bifermentous

3. BIFIDUM PATHWAY: Bifidobacterium bifidum utilizes this pathway. 2glucose +5ADP + 5Pi=3 acetate+ 2 lactase + 5ATP.

APPLICATIONS

lactic acid has a wide range of commercial and household applications.it the food industry, it is used as a food preservative, flavouring agent, pH regulator , to increase shelf life and to control pathogens.

PICKLES

Pickle is a product of LAB prepared by the fermentation of sugars and vegetables.

YOGURT

The main method of preparation of yogurt is by the fermentation of milk and a bacteria called the Lactobacillus bulgaricus.

PHARMACEUTICALS

lactic acid is used an electrolyte in various parental/intravenous solutions. lactic acid is also used in the preparation of dialysis solution for dialysis process.

COSMETIC INDUSTRY

in the cosmetic industry, lactic acid is used in skin care products . it has various functions such as: as a moisturiser, it also works as anti-acne and remove spots from face.

CHEMICAL INDUSTRY

lactic acid is used as a cleaning agent, pH regulator and as anti-microbial agent. since lactic acid contains a carboxyl and hydroxyl group, it can be used to yield various chemical products such as ester.

REFERENCES

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