Boosting protein crops

A high-protein flour derived from rice seeds could pose a threat to premium protein supplements used to boost nutrition levels.

Research showing how transgenic rice seeds could be processed to produce a protein-rich flour was presented yesterday at the American Society of Plant Biologists meeting in Hawaii this week.

Rice seeds are already widely used in the food and beverage industry. But separating the high-quality protein in the seeds, about 6-10 per cent (w/w), from the remaining 70-80 per cent starch content allows for the processing of high-protein rice flour and starch hydrolysates into different products, said Su-May Yu​ from the Academia Sinica in Taipei, Taiwan.

To simplify the production process and improve the cost effectiveness and efficiency of starch bioprocessing, Yu's team highly expressed a thermotolerant and bi-functional starch hydrolase, amylopullulanase (APU), in transgenic rice seeds.

Transgenic rice seeds were then heated at high temperatures. Starch in the seeds was hydrolysed rapidly at these temperatures, and the concentration of soluble sugars increased significantly with incubation time. The more APU present in seeds, the faster the rate of starch hydrolysis to sugars.

The novel APU-transgenic rice seeds produced by the team can be processed to simultaneously produce high-protein rice flour and sugar syrups for human consumption and broad industrial uses, Yu said.

The heat-activated rapid autodrolysis of starch in the seeds would both eliminate the need for the addition of commercial enzymes, but also improves the efficiency of starch bioprocessing. A similar approach could also be applied to other cereals, such as maize, which might offer even lower production costs than rice, added the researchers.