Effect of soy skim from soybean aqueous processing on the performance of corn ethanol fermentation

Techno-Economic Analysis of Integrating Soybean Biorefinery Products into Corn-Based Ethanol Fermentation Operations

With the development of agricultural biorefineries and bioprocessing operations, understanding the economic efficiencies and environmental impacts for these have gradually become popular for the deployment of these industrial processes. The corn-based ethanol and soybean oil refining industries have been examined extensively over the years, especially details of processing technologies, including materials, reaction controls, equipment, and industrial applications. The study focused on examining the production efficiency changes and economic impacts of integrating products from the enzyme-assisted aqueous extraction processing (EAEP) of soybeans into corn-based ethanol fermentation processing. Using SuperPro Designer to simulate production of corn-based ethanol at either 40 million gallons per year (MGY) or 120 MGY, with either oil separation or no oil removal, we found that indeed integrating soy products into corn ethanol fermentation may be slightly more expensive in terms of production costs, but economic returns justify this integration due to substantially greater quantities of ethanol, distillers corn oil, and distillers dried grains with solubles being produced.

The Economic Feasibility of the Valorization of Water Hyacinth for Bioethanol Production

One approach to effectively control the rapid expansion of water hyacinth is to use it as a feedstock in producing valuable goods. While it is technically feasible to produce bioethanol using water hyacinth, the economic feasibility of this valorization is yet unknown. This article conducted an ex-ante cost-benefit analysis of the production of bioethanol from water hyacinth. The results show that in comparison with the active control approach of collection and landfill, it is economically feasible to produce bioethanol from the collected biomass. In addition to its contribution to energy diversification, the production of bioethanol using water hyacinth as a feedstock cannot only control the rapid expansion of water hyacinth but can also contribute to carbon emissions reduction and water quality improvement. While the production cost of bioethanol is high, environmental values play an important role in the economic justification of the production. The coupled use of water hyacinth as a phytoremediation plant and bioethanol feedstock is a potential response to green development strategies.

Recovery of high value-added protein from enzyme-assisted aqueous extraction (EAE) of soybeans by dead-end ultrafiltration

The skim fraction (SF) obtained from enzyme-assisted aqueous extraction (EAE) of soybeans is a by-product with high protein content of up to 60.67%. As such, it is of great interest to develop an efficient method to recover protein from this fraction. In this study, the potential of dead-end ultrafiltration (UF) in recovering skim protein extracted with different proteases was evaluated. Two polyethersulfone (PES) membranes with molecular weight cutoffs (MWCO) of 3 kDa and 5 kDa were utilized. Results revealed that the membrane with the MWCO of 5 kDa exhibited better filtration efficiency, since higher permeate flux values and lower impurity rejections were observed. Compared with Flavourzyme and Protex 7L, Alcalase 2.4L and Protex 6L exhibited stronger hydrolyzing ability, resulting in higher filtration fluxes but lower protein rejection coefficients. The recovered protein showed comparable amino acid profile to SPC, while with significantly reduced levels of trypsin inhibitors and phytate (p < 0.05), indicating high quality of the recovered protein. Overall, UF can be applicable to recover high value-added protein from EAE of soybeans and remove undesired components from the resulting protein products.

Enzyme recycle and fed-batch addition for high-productivity soybean flour processing to produce enriched soy protein and concentrated hydrolysate of fermentable sugars

Despite having high protein and carbohydrate, soybean flour utilization is limited to partial replacement of animal feed to date. Enzymatic process can be exploited to increase its value by enriching protein content and separating carbohydrate for utilization as fermentation feedstock. Enzyme hydrolysis with fed-batch and recycle designs were evaluated here for achieving this goal with high productivities. Fed-batch process improved carbohydrate conversion, particularly at high substrate loadings of 250-375g/L. In recycle process, hydrolysate retained a significant portion of the limiting enzyme α-galactosidase to accelerate carbohydrate monomerization rate. At single-pass retention time of 6h and recycle rate of 62.5%, reducing sugar concentration reached up to 120g/L using 4ml/g enzyme. When compared with batch and fed-batch processes, the recycle process increased the volumetric productivity of reducing sugar by 36% (vs. fed-batch) to 57% (vs. batch) and that of protein product by 280% (vs. fed-batch) to 300% (vs. batch).

Effect of co-products of enzyme-assisted aqueous extraction of soybeans on ethanol production in dry-grind corn fermentation

Enzyme-assisted aqueous extraction processing (EAEP) is an environmentally-friendly alternative to solvent and mechanical oil extraction methods, and can achieve ∼ 97% oil recovery from soybeans. The present study utilized soy skim (protein rich) and insoluble fiber (IF; carbohydrate rich), both co-products of EAEP, in dry-grind corn fermentation. The effects of adding soy skim and untreated IF (UIF), either separately or together, and adding pretreated IF (TIF), on ethanol production were investigated. Maximum ethanol production was achieved when UIF and skim were slurried together (corn-to-UIF ratio 1:0.16; skim-to-UIF ratio 6.5:1) and when fiber-hydrolyzing enzymes were added to corn fermentation. This modification to corn fermentation increased ethanol yield by 20%, ethanol production rate by 3%, and decreased fermentation time by 38 h compared to corn-only fermentation. An attempt was also made to utilize pentoses (from soy skim and IF) in integrated corn-soy fermentation slurry by an additional Escherichia coli KO11 fermentation step.

Pythium irregulare fermentation to produce arachidonic acid (ARA) and eicosapentaenoic acid (EPA) using soybean processing co-products as substrates

Arachidonic acid (ARA) and eicosapentaenoic acid (EPA) were produced by Pythium irregulare fungus using soybean cotyledon fiber and soy skim, two co-products from soybean aqueous processing, as substrates in different fermentation systems. Parameters such as moisture content, substrate glucose addition, incubation time, and vegetable oil supplementation were found to be important in solid-state fermentation (SSF) of soybean fiber, which is to be used as animal feed with enriched long-chain polyunsaturated fatty acids (PUFA). Soybean fiber with 8 % (dwb) glucose supplementation for a 7-day SSF produced 1.3 mg of ARA and 1.6 mg of EPA in 1 g of dried substrate. When soy skim was used as substrate for submerged fermentation, total ARA yield of 125.7 mg/L and EPA yield of 92.4 mg/L were achieved with the supplementation of 7 % (w/v) soybean oil. This study demonstrates that the values of soybean fiber and soy skim co-products could be enhanced through the long-chain PUFA production by fermentation.

Effects of fermentation substrate conditions on corn-soy co-fermentation for fuel ethanol production

Soy skim, a protein-rich liquid co-product from the aqueous extraction of soybeans, was co-fermented with corn to produce ethanol. Effects of soy skim addition level, type of skim, corn particle size, water-to-solids ratio, and urea on co-fermentation were determined. The addition of 20-100% skim increased the fermentation rate by 18-27% and shortened the fermentation time by 5-7h without affecting ethanol yield. Finely ground corn or high water-to-solids ratio (≥ 3.0) in the mash gave higher fermentation rates, but did not increase the ethanol yield. When the water was completely replaced with soy skim, the addition of urea became unnecessary. Soy skim retentate that was concentrated by nanofiltration increased fermentation rate by 25%. The highest level of skim addition resulted in a finished beer with 16% solids, 47% protein (dwb) containing 3.6% lysine, and an ethanol yield of 39 g/100g dry corn.

Solid-state fermentation of soybean and corn processing coproducts for potential feed improvement

Two agro-industrial coproducts, soybean cotyledon fiber and distiller's dried grains with solubles (DDGS), were used as substrates to evaluate the effect of coculturing three different fungi, Aspergillus oryzae, Trichoderma reesei, and Phanerochaete chrysosporium, on enzyme production by solid-state fermentation (SSF). When soybean fiber was used as the substrate, a maximum xylanase activity of 757.4 IU/g and a cellulase activity of 3.2 IU/g were achieved with the inoculation and incubation of T. reesei and P. chrysosporium for 36 h, followed by A. oryzae for an additional 108 h. This inoculation scheme also resulted in the highest xylanase activity of 399.2 IU/g compared to other fungi combinations in the SSF of DDGS. A large-scale SSF by this fungus combination produced fermented products that had xylanase and cellulase activities of 35.9-57.0 and 0.4-1.2 IU/g, respectively. These products also had 3.5-15.1% lower fiber and 1.3-4.2% higher protein contents, suggesting a potential feed quality improvement.