Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers Get To The Root Of Cassava’S Cyanide-Producing Abilities

13.05.2003


Cassava is the third-most important food source in tropical countries, but it has one major problem: The roots and leaves of poorly processed cassava plants contain a substance that, when eaten, can trigger the production of cyanide.


A cassava plant usually reaches 3 to 4 feet in height, though some plants can grow up to 13 feet tall.


Cyanogens in cassava plants convert to cyanide when raw cassava is eaten or processed.



That’s a serious problem for the 500 million people who rely on cassava as their main source of calories, among them subsistence farmers in Sub-Saharan Africa, said Richard Sayre, a professor of plant biology at Ohio State University. He and his colleague Dimuth Siritunga, a postdoctoral researcher in plant biology at the university, have created cyanogen-free cassava plants. A cyanogen is a substance that induces cyanide production.

Their study appeared in a recent issue of the journal Planta.


Cassava is a hardy plant – it can remain in the ground for up to two years and needs relatively little water to survive. It’s the key source of carbohydrates for subsistence farmers in Africa. But an unprocessed cassava plant contains potentially toxic levels of a cyanogen called linamarin.

The proper processing of cassava – drying, soaking in water, rinsing or baking – effectively reduces cassava’s linamarin content. But, said Sayre, shortcut processing techniques, which are frequently used during famines, can yield toxic food products.

“If we could eliminate the cyanogens in cassava, the plant wouldn’t need to be processed before it’s eaten,” he said. “In Africa, improperly processed cassava is a major problem. It’s associated with a number of cyanide-related health disorders, particularly among people who are already malnourished.”

Chronic, low-level cyanide exposure is associated with the development of goiter and with tropical ataxic neuropathy, a nerve-damaging disorder that renders a person unsteady and uncoordinated. Severe cyanide poisoning, particularly during famines, is associated with outbreaks of a debilitating, irreversible paralytic disorder called Konzo and, in some cases, death. The incidence of Konzo and tropical ataxic neuropathy can be as high as 3 percent in some areas.

People who get little or no protein in their diets are particularly susceptible to cyanide poisoning, as they lack the proper amino acids necessary to help detoxify the poison.

Sayre and Siritunga engineered cassava plants in which the expression of the genes responsible for linamarin synthesis was blocked. They then analyzed the linamarin content in these plants’ leaves and roots, finding a significant reduction of the cyanogen in leaves (by 60 to 94 percent) and in roots (by 99 percent) compared to normal cassava plants.

Cassava leaves contain more linamarin than do the plant’s roots, Sayre said. Plant biologists believe that somehow linamarin is transported from the leaves to the roots early in a plant’s life. Turning off the linamarin-inducing genes in cassava leaves might reduce the levels of linamarin in the plant’s roots.

“When leaf linamarin was reduced by 40 percent, the roots contained less than 1 percent of the cyanogen,” Sayre said, adding that it’s critical for the leaves of a growing cassava plant to contain a small amount of linamarin.

“Linamarin protects cassava from being eaten by insects or animals,” he said. “Plants with moderate linamarin levels in their leaves and that contain nearly no linamarin in their roots are both protected from herbivores and contain far less of the cyanogen in their roots.”

Cyanide forms when cassava is processed. But the toxin is volatile and is released into the air, rather than remaining in the food. Correct processing methods ensure that the cyanogen content in cassava plants will be within an acceptable range, Sayre said. (The United Nations’ Food and Agriculture Organization has established maximum recommended cyanide levels for foods.)

“In African countries, it’s mostly women and children who are susceptible to cyanide poisoning,” Sayre said. “Women are usually charged with processing the plant, which leaves them susceptible to inhaling cyanide gas. Cyanide can poison a person by either inhalation or ingestion.”

The shelf life of a cassava root is very short once it’s removed from the stem, so there’s an urgency to get the food to market.

“Roots can turn to mush in less than a week,” Sayre said. “Cassava’s fresh market time is very small, so it has to be processed immediately.”

And that’s where consumers can run into problems -- the rush to get cassava to the market may keep some batches of cassava from being processed properly. Even if the plant is properly processed, exposure to the volatile cyanide can cause health problems in people charged with processing the roots and leaves.

While cassava roots contain less than 10 percent of the linamarin level found in cassava leaves, it’s the long-term exposure to cyanide that presents a threat to humans.

“Linamarin is converted to cyanide when eaten,” Sayre said. “Repeated exposure of low doses of cyanide over time can lead to health problems.

“But these cyanogen-free plants represent a safer and more marketable food product as well as a tool to determine the role of cyanogens in protection against insect pests and crop productivity.”

“However, preliminary studies indicate that linamarin may be important in the transport of nitrogen from cassava leaves to its roots in young plants,” he continued. “Plants producing varying levels of linamarin need to be tested in field trials to determine if the inhibition of linamarin synthesis affects plant yield.”

Grants from the Rockefeller Foundation, the Consortium for Plant Biotechnology Research, the Cassava Biotechnology Network and Ohio State University supported this research.


Contact: Richard Sayre, 614-292 2587; Sayre.2@osu.edu
Written by Holly Wagner, 614-292-8310; Wagner.235@osu.edu

Holly Wagner | Ohio State University
Further information:
http://www.osu.edu/researchnews/archive/cassava.htm
http://link.springer-ny.com/link/service/journals/00425/

More articles from Agricultural and Forestry Science:

nachricht Advance warning system via cell phone app: Avoiding extreme weather damage in agriculture
12.07.2018 | Leibniz-Zentrum für Agrarlandschaftsforschung (ZALF) e.V.

nachricht Fishy chemicals in farmed salmon
11.07.2018 | University of Pittsburgh

All articles from Agricultural and Forestry Science >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Research finds new molecular structures in boron-based nanoclusters

13.07.2018 | Materials Sciences

Algae Have Land Genes

13.07.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>