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Inedible plant material may be convertible to food

April 16, 2013
Courtesy of Virginia Tech
and World Science staff

Re­search­ers say they have man­aged to turn an in­ed­i­ble plant ma­te­ri­al called cel­lu­lose in­to starch—po­ten­tially open­ing up a huge new nu­tri­ent source for hu­man­ity.

Starch can be ed­i­ble by peo­ple if its qual­ity is high enough. It’s in fact a ma­jor com­po­nent of the hu­man di­et, pro­vid­ing an es­ti­mat­ed 20 to 40 per­cent of our daily ca­lor­ic in­take.

Y.H. Per­ci­val Zhang, a bi­ol­o­gist at Vir­gin­ia Tech Col­lege of Ag­ri­cul­ture and Life Sci­ences, led the proj­ect, aimed at help­ing feed a world popula­t­ion es­ti­mat­ed to swell to 9 bil­lion by 2050. The find­ings are pub­lished this week in the early edi­tion of the jour­nal Pro­ceed­ings of the Na­t­ional Acad­e­my of Sci­ences.

Cel­lu­lose is the sup­port­ing ma­te­ri­al in plant cell walls and a ma­jor com­po­nent of wood. It’s al­so the most com­mon car­bo­hy­drate, one of the four ma­jor clas­ses of bi­o­log­i­cal molecules, on Earth. The new work opens the door to the po­ten­tial that food could be cre­at­ed from any plant, re­duc­ing the need to grow crops on val­u­a­ble land re­quir­ing fer­til­iz­ers, pes­ti­cides, and lots of wa­ter, Zhang said. 

His team pro­duced a type of starch called am­yl­ose, suit­a­ble for hu­man con­sump­tion if it is high enough qual­ity; low­er grades can be used in an­i­mal feed, and in a range of oth­er ap­plica­t­ions, the sci­en­tists said. Am­yl­ose is­n’t bro­ken down dur­ing di­ges­tion, is a good source of fi­ber and has been found to lower the risk of obes­ity and di­a­be­tes. 

“Be­sides serv­ing as a food source, the starch can be used in the ma­n­u­fac­ture of ed­i­ble, clear films for bi­o­de­grada food pack­ag­ing,” Zhang said. “It can even serve as a high-dens­ity hy­dro­gen stor­age car­ri­er that could solve prob­lems re­lat­ed to hy­dro­gen stor­age and dis­tri­bu­tion.”

The team used a new pro­cess in­volv­ing a chem­i­cal sys­tem known as cas­cad­ing en­zymes. En­zymes are or­gan­ic sub­stances that that speed up chem­i­cal re­ac­tions. “Cel­lu­lose and starch have the same chem­i­cal for­mu­la,” Zhang ex­plained. “The dif­fer­ence is in their chem­i­cal link­ages. Our idea is to use an en­zyme cas­cade to break up the bonds in cel­lu­lose, en­a­bling their re­con­figura­t­ion as starch.”

The sys­tem takes cel­lu­lose from non-food plant ma­te­ri­al, such as corn stov­er, con­verts about 30 per­cent to am­yl­ose, and breaks down the rest to glu­cose, or sug­ar, suit­a­ble for eth­a­nol pro­duc­tion. Corn stov­er con­sists of the stem, leaves, and husk of the corn plant re­main­ing af­ter ears of corn are har­vested. How­ev­er, the pro­cess works with cel­lu­lose from any plant, Zhang said.

The pro­cess, called “si­mul­ta­ne­ous en­zy­mat­ic bio­trans­forma­t­ion and mi­cro­bi­al fer­menta­t­ion,” is easy to scale up for com­mer­cial pro­duc­tion, the re­search­ers claimed. They added that it’s en­vi­ron­men­tally friendly be­cause it does not re­quire ex­pen­sive equip­ment, heat, or chem­i­cal reagents, and gen­er­ates no waste. The key en­zymes are fixed on­to sub-microscopic, mag­net­ic “nanopar­t­i­cles” de­signed to be easily re­cy­cled. The pro­cess is cov­ered un­der a pro­vi­sion­al pat­ent ap­plica­t­ion, Zhang said.


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Researchers say they have managed to turn an inedible plant material called cellulose into starch—potentially opening up a huge new nutrient source for humanity. Starch can be edible by people if its quality is high enough. It’s is a major component of the human diet, providing an estimated 20 to 40 percent of our daily caloric intake. Y.H. Percival Zhang a biologist at Virginia Tech College of Agriculture and Life Sciences, led the project, aimed at helping feed a world population estimated to swell to 9 billion by 2050. The findings are published this week in the early edition of the journal Proceedings of the National Academy of Sciences. Cellulose is the supporting material in plant cell walls and a major component of wood. It’s also the most common carbohydrate, one of the four major classes of biological molecules, on Earth. The new work opens the door to the potential that food could be created from any plant, reducing the need to grow crops on valuable land requiring fertilizers, pesticides, and lots of water, Zhang said. His team produced a type of starch called amylose, suitable for human consumption if it is high enough quality; lower grades can be used in animal feed, and in a range of other applications, the scientists said. Amylose isn’t broken down during digestion, is a good source of fiber and has been shown to decrease the risk of obesity and diabetes. “Besides serving as a food source, the starch can be used in the manufacture of edible, clear films for biodegradable food packaging,” Zhang said. “It can even serve as a high-density hydrogen storage carrier that could solve problems related to hydrogen storage and distribution.” The team used a new process involving a chemical system known as cascading enzymes. Enzymes are organic substances that that speed up chemical reactions. “Cellulose and starch have the same chemical formula,” Zhang explained. “The difference is in their chemical linkages. Our idea is to use an enzyme cascade to break up the bonds in cellulose, enabling their reconfiguration as starch.” The system takes cellulose from non-food plant material, such as corn stover, converts about 30% to amylose, and breaks down the rest to glucose, or sugar, suitable for ethanol production. Corn stover consists of the stem, leaves, and husk of the corn plant remaining after ears of corn are harvested. However, the process works with cellulose from any plant, Zhang said. This process, called “simultaneous enzymatic biotransformation and microbial fermentation,” is easy to scale up for commercial production, the researchers claimed. They added that it’s environmentally friendly because it does not require expensive equipment, heat, or chemical reagents, and generates no waste. The key enzymes are fixed onto sub-microscopic, magnetic “nanoparticles” designed to be easily recycled. The process is covered under a provisional patent application, Zhang said.