By Flora Mauch, Checkbiotech

Give us day by day our daily bread – this is the Christian prayer for basic food. For some it would be a Godsend to be able to incorporate the starch qualities from wheat into other plants so that they could also be used to produce starch.

Bread consists of starch, a complex carbohydrate made up of many glucose molecules linked together and also found in other foods such as potatoes, rice, and corn.

Yet, starch is not limited to food. It is also used to produce products, such as paper, glue, textiles and building materials. This is due to starch’s sticky property that enables it to give the end product the desired texture.

In order to make starch, plants collect energy from the sun in a process called photosynthesis. Many plants store the energy produced during photosynthesis process in the form of glucose, which in turn is stockpiled to starch. This carbohydrate consists of two forms of glucose units, amylose and amylopectin, differing in their glucose linkage.

The properties of starch, which are important in food production and for industrial uses, vary with the relative accumulation of these two major components. Cooking and textural characteristics depend not only on the ratio of amylopectin to amylose, but also on the degree of amylopectin branching. In general one can say that the higher the branching of amylopectin, the more favorable it is for industrial uses.

Modifying this parameters is not a new idea. Usually, it has been accomplished using chemical or physical methods. Of late, biotechnological alternatives are found in the use of enzymes.

The latest example is created by the team of Dr. Baek Hie Nahm from the Department of Bioscience and Bioinformatics of the Myongji University. Having known which gene led to the production of an enzyme responsible for processing amylopectin branching, Dr. Nahm transfer the same gene into rice plants.

As a result, they obtained transgenic rice with an increased degree of amylopectin branching. In this way, starch is already being modified while the rice is sprouting, what biologists call an in vivo modification. Thus, at the time of harvest, the starch features all the properties important for the industrial uses.

Letting the genetically modified plant carry out the starch-modifying process, eliminates the chemical or physical treatment that is presently required. This facilitates the convenience of a fast and efficient starch production at a more economical and environmentally friendly price.

In vivo modification of starches using genetic engineering holds potential for both enhancing nutritional qualities and for obviating post-harvest modifications.

Dr. Baek Hie Nahm delineates the present situation, “Further studies are required to examine if this modified starch exhibits properties that are desirable for human consumption. Current and further research will bring to light a more complete picture of the complex and intriguing mechanism of starch synthesis.”

Contact:
Professor Baek Hie Nahm
Department of Bioscience and Bioinformatics
Myongji University
449-728 Yongin, Korea
Email: bhnahm@mju.ac.kr
Phone: +82-31-3306193

Expression of Escherichia coli branching enzyme in caryopses of transgenic rice results in amylopectin with an increased degree of branching. Planta