Evaluation of Enzyme Activity and Fiber Content of Soybean Cotyledon Fiber and Distiller’s Dried Grains with Solubles by Solid State Fermentation

Abstract

To increase the value of coproducts from corn ethanol fermentation and soybean aqueous processing, distiller's dried grains with solubles (DDGS) and soybean cotyledon fiber were used as the substrates for solid state fermentation (SSF) to improve feed digestibility. Aspergillus oryzae, Trichoderma reesei, and Phanerochaete chrysosporium were chosen as they produce desirable enzymes and are widely used in SSF for feed. The results showed that the cellulase and xylanase activities were significantly increased after 7 days of fermentation, and cellulose and hemicellulose degradation was also greatly increased. When soybean fiber was used as SSF substrate, the maximum activities of the cellulase and xylanase were 10.3 and 84.2 IU/g substrate (dry weight basis) after SSF treatment, respectively. However, the enzyme activities were relatively low in DDGS, and the growth of the three fungi was poor. The fungi grew better when soybean cotyledon fiber was added to DDGS, and cellulase and xylanase activity increased with the increase of soybean fiber content. Porosity was identified as an important factor for SSF because the addition of inert soybean hull alone improved the fungi growth significantly. These data suggest that the nutritional value of DDGS and soybean cotyledon fiber as monogastric animal feed could be greatly enhanced by SSF treatment.

Solid-State Fermentation of Soybean and Corn Processing Coproducts for Potential Feed Improvement

“…Soybean fiber with an original moisture content of 85% was adjusted to a moisture content of 75% by using soybean hulls, and the pH was adjusted to 5.0 as reported. 17 DDGS was hydrated to 85% of moisture and was adjusted to a moisture content of 75% with soybean hulls, using the same amount as for soybean fiber. Soybean hulls improve the porosity of substrates for better fungal growth as demonstrated in our previous study.…”

“…SSF of soybean cotyledon fiber and DDGS with the three individual fungi A. oryzae, T. reesei, and P. chrysosporium were previously investigated by Yang et al, 17 but the effect of coculturing using various combinations of the fungi was unknown. Thus, the objectives of this study were (1) to investigate if there is any synergistic effect among the three fungi based on the xylanase and cellulase production, (2) to determine the best combination of fungi for large-scale SSF, and (3) to examine the compositional change in soybean cotyledon fiber, DDGS, and soy-enhanced DDGS after largescale SSF.…”

Using soybean and corn processing co-products in different fermentation systems

“…Based on our previous study 2 of best fungus growth at moisture content of 75% or 70% as in Table 1, soybean fiber was adjusted to a moisture content of 75% using soybean hulls, which acted as inert materials to improve the porosity of the substrate and promoted better growth of fungi. 2 Previous results showed that 4% glucose might not be sufficient for P. irregulare to grow, therefore, different level of glucose was added to the substrate to investigate PUFA production. Table 3 shows the fatty acid composition of these treatments.…”

“…SSF has been studied intensively for the production of enzymes, antibiotics, surfactants, and other value-added products. 2 Compared to the submerged fermentation in which nutrients are present in dissolved form in a large amount of water, SSF shows a great commercial potential due to its lower waste water production and operating expenses, simpler fermentation media requirement, superior productivity, and easier prevention of bacterial contamination. EAEP produces soybean cotyledon fiber and soy skim as co-products.…”

“…Our previous study showed that the fiber composition can be improved by enzyme-producing fungi through solid-state fermentation (SSF). 2 The fermented soybean fiber with reduced fiber and increased protein content can be used as non-ruminant feed. Soy skim is a liquid fraction from EAEP that contains partially hydrolyzed protein and has been shown to be an excellent nutrient source for corn ethanol fermentation.…”