FIELD OF THE INVENTION:
This invention relates to a process for the preparation of lactic acid from starchy agro residues.
BACKGROUND OF THE INVENTION:
Lactic acid is a commonly known organic acid. It is attracting much attention because of its varied application from food, textile to pharmaceutical industry. It is generally recognized as safe (GRAS) for use as food additives by the regulatory agencies like FDA in USA. There are two isomeric forms of lactic acid because of the presence of a chiral centre: L (+) lactic acid and D (-)lactic acid. Among them D (-) lactic acid is harmful to human metabolism and can result in acidosis and decalcification. So, L (+) lactic acid is in high demand. Productions of only L (+) form of Lactic acid for cost effective procedure is the area of focus for recent researchers. Till date, many agro residues are used for lactic acid production.
U.S. Patent No. 0036062 explains the production of lactic acid from agro waste molasses and cane bagasse as a raw material. U.S. Patent No. 4816267 shows the production of lactic acid with waste liquor of soyabean having very low protein content. U.S. Patent No. 5506123 uses organic portion of a waste stream to produce lactic acid. It has been seen that the chemical synthesis from petrochemical resources produces racemic DL-lactic acid whereas microbial fermentation increases its purity and also reduces the cost of manufacturing. Thus, investigation for production from renewable sources is of great importance.
OBJECTS OF THE INVENTION:
It is therefore an object of this invention to propose a process for the preparation of lactic acid which is highly pure.

It is a further object of this invention to propose a process for the preparation of lactic acid which utilizes waste and is therefore cost effective and simple.
Another object of this invention is to propose a process for the preparation of lactic acid, which avoids the use of harmful chemicals, and is eco-friendly.
There and other objects and advantages of the invention which will be apparent from the ensuing description.
DETAILED DESCRIPTION OF THE INVENTION:
This invention has provided a process for the preparation of lactic acid from starchy agro-residues.
In accordance with this invention, is provided, a process for the production of L (+) lactic acid from a microbial source which solely produces L (+) lactic acid. Different renewable resources were tried for production of lactic acid.
Zizyphus oenophia, one of the potent starchy agro residues (70.05% starch), potato waste (50.01% starch) and cheese whey (4.5-5% lactose) were used as the starting raw materials for lactic acid production.
The media used for the fermentation is MRS media having the composition of Sodium acetate (3.5-5.5 g/L), Tri ammonium citrate (1.5-3 g/L), di-sodium hydrogen phosphate (1.5-3.5 g/L), Magnesium sulphate (0.025-0.25 g/L), Manganese sulphate (0.025-0.15 g/L), Tween 80 (0.5-3 ml/L).

The organism Lactobacillus amylopMus GV6 anaerobically produces only L (+) lactic acid. Optimized process conditions ranges were pH 5.0-6.5, inoculum volume 2-3% (v/v) having 109 cells/ml, temperature 30-35 °C and substrate: media ratio 1-1.5 which resulted in 95.09% (v/v) starch conversion with an incubation period of 72-96 h.
Optimum conversion of 95.09% starchy material of Zizyphus oenophlia was recorded within a time span of 48h-100 h at initial pH of 5.0-6.5. Whereas, for potato waste the conversion was 79.89% and cheese whey as substrate depicted 93.23% (vIv) lactose conversion to lactic acid.
The strain Lactobacillus amylophilus GV6 is a potent probiotic strain and has been used to secrete amylopullulanase and directly convert starch to lactic acid in a single step.
The strain Lactobacillus amylophilus GV6 capable for breakdown of linkages such as 0-1,4; 0-1,6 bonding present in the starchy materials. It is Lactobacillus amylophilus GV6 which is capable of converting starch present in Zizyphus oenophlia directly into L (+) form of lactic acid.
The strain has never been used before for Lactic acid production. This leads to up to 10 fold increase in lactic acid production, over prior art methods.
The biochemical composition of all the substrates was evaluated to ensure
its suitability as raw materials for lactic acid production. Various factors
showing effect on lactic acid production by Lactobacillus amylophilus GV6 has been
thoroughly studied. The productivity was found to be affected by many factors:
(1) inoculum volume, (2) temperature, (3) substrate concentration, (4)
incubation period, etc. Optimization of fermentation conditions has
been performed by a statistical technique i.e. response surface

methodology and it was found that L. amylophilus GV6 was efficiently able to convert starch to lactic acid in 96 hrs in a single step.
The invention will now be explained in greater details with the help of the following non-limiting example.
EXAMPLE:
RAW MATERIALS:
Cheese whey, potato waste and Fruits of Zizyphus oenophilia were obtained from campus of IIT Kharagpur. Organism used is Lactobacillus amylophilus GV6. The fruits were air dried, milled and stored at room temperature for subsequent use.
Fermentation
Production of lactic acid is done through optimization process. Cultures of Lactobacillus amylophilus GV6 were incubated for 48-96 h for direct conversion of starch to lactic acid. The fermented broth containing lactic acid was centrifuged at 8,000 rpm for 15-20 minutes. The clear supernatant of lactic acid was obtained. Estimation of lactic acid was done through Kimberley and Taylor Method.
The lactic acid produced according to the invention is rarely found where potent starchy agro residue may be used for the production of the lactic acid. An optimum conversion of up to 90% is possible with this method.

WE CLAIM:
1. A process for the production of lactic acid comprising the steps of providing a substrate in a medium and inoculating the same with an inoculum comprising Lactobacillus amylophilus GV6, subjecting the substrate to fermentation to obtain a fermented broth followed by centrifugation of the broth to obtain lactic acid from the supernatant.
2. The process as claimed in claim 1, wherein said substrate is selected from Zizyphus oenophlia, potato waste, cheese whey.
3. The process as claimed in claim 1, wherein fermentation is effected with an inoculum volume 2 to 3% (v/v) having 109 cells/ml.

4. The process as claimed in claim 1, wherein fermentation is effected at a temperature in the range of 30 to 35°C.
5. The process as claimed in claim 1, wherein the substrate: media ratio is 1:1.5.

6. The process as claimed in claim 1, wherein the fermentation is carried out at a pH in the range of 5.0 to 6.5.
7. The process as claimed in claim 1, wherein the substrate is fermented for an incubation period of 48 to 120 hours.

8. The process as claimed in claim 1, wherein the medium used for fermentation is MRS media having the composition of Sodium acetate (3.5-5.5 g/L,, Tri ammonium citrate (1.5-3 g/L), di-sodium hydrogen phosphate (1.5-3.5 g/L,, Magnesium sulphate (0.025-0.25 g/L), Manganese sulphate (0.025-0.15 g/L), Tween 80 (0.5-3 ml/L).
9. The process as claimed in claim 1, wherein the lactic acid produced through fermentation is producing solely L (+) form of lactic acid.