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 Brazilian Beef Industry Moves to Reduce Its Destruction of Rain Forests
13.05.2015 | University of Wisconsin-Madison

nachricht The hairy past - Tail hair as an indicator of behaviour and ecology in horses
07.05.2015 | Veterinärmedizinische Universität Wien

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: IoT-based Advanced Automobile Parking Navigation System

Development and implementation of an advanced automobile parking navigation platform for parking services

To fulfill the requirements of the industry, PolyU researchers developed the Advanced Automobile Parking Navigation Platform, which includes smart devices,...

Im Focus: First electrical car ferry in the world in operation in Norway now

  • Siemens delivers electric propulsion system and charging stations with lithium-ion batteries charged from hydro power
  • Ferry only uses 150 kilowatt hours (kWh) per route and reduces cost of fuel by 60 percent
  • Milestone on the road to operating emission-free ferries

The world's first electrical car and passenger ferry powered by batteries has entered service in Norway. The ferry only uses 150 kWh per route, which...

Im Focus: Into the ice – RV Polarstern opens the arctic season by setting course for Spitsbergen

On Tuesday, 19 May 2015 the research icebreaker Polarstern will leave its home port in Bremerhaven, setting a course for the Arctic. Led by Dr Ilka Peeken from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) a team of 53 researchers from 11 countries will investigate the effects of climate change in the Arctic, from the surface ice floes down to the seafloor.

RV Polarstern will enter the sea-ice zone north of Spitsbergen. Covering two shallow regions on their way to deeper waters, the scientists on board will focus...

Im Focus: Gel filled with nanosponges cleans up MRSA infections

Nanoengineers at the University of California, San Diego developed a gel filled with toxin-absorbing nanosponges that could lead to an effective treatment for skin and wound infections caused by MRSA (methicillin-resistant Staphylococcus aureus), an antibiotic-resistant bacteria. This "nanosponge-hydrogel" minimized the growth of skin lesions on mice infected with MRSA - without the use of antibiotics. The researchers recently published their findings online in Advanced Materials.

To make the nanosponge-hydrogel, the team mixed nanosponges, which are nanoparticles that absorb dangerous toxins produced by MRSA, E. coli and other...

Im Focus: ORNL demonstrates first large-scale graphene fabrication

One of the barriers to using graphene at a commercial scale could be overcome using a method demonstrated by researchers at the Department of Energy's Oak Ridge National Laboratory.

Graphene, a material stronger and stiffer than carbon fiber, has enormous commercial potential but has been impractical to employ on a large scale, with...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International symposium: trends in spatial analysis and modelling for a more sustainable land use

20.05.2015 | Event News

15th conference of the International Association of Colloid and Interface Scientists

18.05.2015 | Event News

EHFG 2015: Securing health in Europe. Balancing priorities, sharing responsibilities

12.05.2015 | Event News

 
Latest News

A non-invasive tool for diagnosing cancer*

21.05.2015 | Medical Engineering

Gamma ray camera may help with Fukushima decontamination*

21.05.2015 | Power and Electrical Engineering

Laser technology advances microchip production*

21.05.2015 | Process Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>