**Soybean as a Nitrogen Supplier**

Matsumiya Yoshiki, Horii Sachie, Matsuno Toshihide and Kubo Motoki

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/51017

**1. Introduction**

Soybean has been cultivated all over the world since ancient times for its high protein and lipid content. It is one of the most important agricultural products in the world and its glob‐ al production is more than 220 million tons per year [1]. Vegetable oil production from soy‐ bean is the highest among plant oils (30%) [2].

Soybean is used directly as food in Japan and several Asian countries. Recently, soybean protein was recognized as both healthy and tasty and is used in food such as Tofu and soy sauce. Soybean-meal, which remains after extraction of the vegetable oil, contains about 50% protein with well balanced amino acids. Therefore, soybean-meal is often re-utilized as ani‐ mal foodstuff.

Soybean waste was utilized as an organic fertilizer prior to the 1940s [3-6]. However, a chemical fertilizer took the place of the organic fertilizer because it produced faster results. Organic fertilizers are now gradually being used again for increased food production safety and the protection of the environment.

Soybean cultivation is well known for improving soil fertility [3, 7, 8]. Root-nodules are formed by the soybean plant, and atmospheric N2 is fixed by the nitrogen fixing bacteria in the root-nodule [9]. N2 is converted to NH4 <sup>+</sup> by nitrogenase from these nitrogen fixing bacte‐ ria, and this NH4 + is supplied to the soil environment.

Recently, investigations into the utilization of proteins from soybean waste have been carried out for the development of high quality foods. Protein fractions, such as soy protein isolates and whey protein are industrially produced, and these fractions are used as additives for the im‐ provement of food nutrition [10]. Moreover, several soybean proteins and peptides have been

purified and utilized as medicines for hypotension, rheumatism, and cholesterol control [11-13]. The bioactive peptides of soybean protein have also been investigated [5, 6].

This chapter explains how soybean cultivation and soybean protein are nitrogen suppliers and describes the production of novel bioactive peptides from soybean and legumes.
