Poster: Enzymology

Abs # 235: Transgenic Rice Expressing a Thermostable Amylopullulanase in Seeds Leads to Starch Autohydrolysis and Production of High-protein Flour

Presenter:	Chiang, Chih-Ming , junming@gate.sinica.edu.tw
Authors	Chiang, Chih-Ming  (A) (C)  Shaw, Jei-Fu  (B)   Yu, Su-May  (C)
Affiliations:	(A): Graduate Institute of Life Science, National Defense University (B): Institute of Bontany, Academia Sinica, Taiwan, R.O.C (C): Institute of Molecular Biology, Academia Sinica, Taiwan, R.O.C
Web Site:	http://junming@gate.sinica.edu.tw

Commerical bioprocessing of starch and production of high-protein flour from plant storage organs use thermostable microbal enzymes to accelerate starch hydrolysis and seperation of protein from sugars. With the aim of improving the cost effectiveness and efficiency of bioprocessing, transgenic rice seeds producing hydrolytic enzymes were examined as a strategy. Amutant Apu gene, which was isolated from a thermobacterium, encides a truncated form of amylopullulanase ( APU ) possesing thermostable a-amylase and pullulanase activities. Rice was genetically engineered for expression of the truncated form of APU in seeds under the control of glutelin or aa-amylase gene promoters. These studies observed no adverse effect on plant development, seed formation or seed starch accumulation. However, amylose content was generally reduced, with the reduction correlating inversely with APU activities in transgenic seeds. Rice seeds containing different amounts of amylose, which affects starch quality, could therefore be obtained by expressing various levels of APU. Seeds heated to 85oC resulted in complete conversion of starch into soluble sugars and production of high-protein rice flour within a few hours, depending on the levels of APU present in these seeds. This study established novel approaches that can alter amylose content in seeds, accelerate bioprocessing of starch, and produce nutrition-improved high-protein flour from rice seeds. In addition to potential applications in industry, the novel rice seeds may also offer people in developing countries an easily accessible and important source of nutrition-improved high-protein rice flour in their diets.