The Use of Rice Seed as a Bioreactor

Rice (Oryza sativa L.) is a prime staple food consumed by half of the world’s population and is an agronomically familiar crop grown on every populated continent. Additionally, rice seeds are suitable production platform for molecular farming with low development costs, prompt and virtually limitless production scale-change, significant lower risk of pathogen pollution than microbial and animal systems. From long dietary experience, everyone knows that rice don’t contain pathogens, especially rice seeds, because they are eaten as staple food for a long time ago. Rice seeds with various high-value recombinant proteins have been developed in companies and research institutions worldwide using various novel strategies. Recombinant products produced by other major expression platforms such as microorganisms, cultured cell, and tobacco transient expression system usually need purification before use. Rice seed can be used like the above platforms. However, one of the most important advantages of the use of rice seed is the potential for direct oral delivery through the everyday meal, without the need for purification. Additionally, rice has quite suitable transformation systems, high level accumulation of recombinant proteins, and higher grain yields than other cereals under typical cultivation condition. Surprisingly, recombinant proteins accumulated in rice seeds are stably maintained for several years even at room temperature, eliminating the requirement for refrigeration in locations where this is prohibitively expensive. The use of rice seeds as bioreactor will be beneficial as a production tool for pharmaceutical, nutraceutical, and industrial proteins in coming times. The chapter presents the various strategies being used for producing recombinant proteins in rice seed, molecular behaviors of such a recombinant protein in rice seed cells, and examples of genetically modified rice seed accumulating high-value recombinant proteins.