Potato plugged as new lactic acid source

By Anthony Fletcher

- Last updated on GMT

Related tags Lactic acid Starch

Potato waste could offer the food industry a cheap, renewable and
as yet underutilised source of chitin and lactic acid, according to
a university scientist.

Washington state university's Dr Shulin Chen has identified cull potatoes, with their rich composition in starch and nutrients, as a potentially ideal raw material for the production of these important compounds.

And with the wholesale price for lactic acid currently at about 50 cents per pound and $4,500 a pound for pure chitin, Chen is confident that the fermentation and separation process he is working on for cull potatoes could revolutionize both the ingredients industry - and the fortunes of potato growers.

Lactic acid is a colourless compound, commonly used as a food additive for flavour and preservation. It is usually produced chemically from coal, petroleum, and natural gas, or biologically from the bioconversion of carbohydrates and plant biomass.

Chitin on the other hand is found primarily in the exoskeletons of crustaceans as well as in the cell walls of some fungi. But studies on the production of lactic acid from potatoes using the fungal strain Rhizopus oryzae NRRL 395 have found that a considerable amount of fungal biomass is produced at the same time.

This fungal mass has a cellular wall composed primarily of chitin, which has been found to have several nutritional and physiological benefits.

Now Chen believes that cull potatoes could provide the raw material needed to dramatically increase production. Research in this sector has grown rapidly, and could possibly be implemented in processing plants across the United States within the next five years.

The biggest problem Chen faces however is how to make his process economically feasible.

"It is not a question of if it can be done,"​ Chen said. "The technology is there. It's a matter of reducing the associated costs."

The means are certainly available. Culls cannot be sold on the fresh market or processed into French fries or other potato products because they do not meet minimum size, grade or quality standards.

They are often are sent on for further processing, fed to cattle or added to compost piles. Potatoes cost about $70 to $120 per ton to grow while growers generally receive less than $10 a ton for their culls.

But with 15.44 percent potato starch content and a yield of 60 percent of glucose to lactic acid, cull potatoes can be converted to approximately 94.5 million pounds of lactic acid. At the current wholesale price of $0.50 per pound of lactic acid, the estimated total value in Washington State alone would be $47 million.

In addition to increasing lactic acid and chitin production, Chen's technology could also potentially reduce the environmental impact of potato waste and the wastewater generated during processing.

Wastewater generally is applied to land but because it contains some quantities of starch, protein, nitrogen and phosphate, any form of land application must be closely monitored. But the new technology utilizes the starch and protein from wastewater as well as the culls.

An Invention Disclosure for the process was submitted to Washington State University Research Foundation (WSURF) on 20 December 2004.

Related topics Science Cultures, enzymes, yeast

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