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Abstract
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Among the vegetarian protein sources, soybean meal is the most important vegetable protein source because it contains high protein level and an excellent balance of indispensable AA. However, soybean meal contains anti-nutritional factors such as lectins, trypsin inhibitors, and oligosaccharides that decrease nutrient availability and affect growth performance of fish. This study examined the effects of radiation (gamma ray), fermentation (Saccharomyces cerevisiae) and the combined effect of these two methods on quantity and quality of this protein source for use in fish diets. For this purpose, soybean meal with five treatments including: Control (untreated soybean meal), gamma rays at doses of 15 (15ISB) kGy, 30 (30ISB) kGy, fermented (FSB) and the combination of gamma and fermentation (IFSB 15) were treated and changes in crude protein, amino acid composition and electrophoresis (SDS-PAGE) of proteins was studied. The results showed that irradiation of soy had no effect on its crude protein, amino acid composition and protein quality. However, use of fermentation or combination of fermentation and irradiation increased soy protein. Generally these results suggest that gamma irradiation and fermentation can be used as a new approach to reduce anti-nutrients and enhance the nutritional value of soybean meal for fish diets.
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