Recoveries of oil and hydrolyzed sugars from corn germ meal by hydrothermal pretreatment: a model feedstock for lipid-producing energy crops

Authors: JIA, YUYAO - University Of Illinois; KUMAR, DEEPAK - State University Of New York- College Of Environmental Science And Forestry; Moser, Jill; Dien, Bruce; SINGH, VIJAY - University Of Illinois

Submitted to: Energies
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/2020
Publication Date: 11/18/2020
Citation: Jia, Y., Kumar, D., Moser, J.K., Dien, B.S., Singh, V. 2020. Recoveries of oil and hydrolyzed sugars from corn germ meal by hydrothermal pretreatment: a model feedstock for lipid-producing energy crops. Energies. 13(22). Article 6022. https://doi.org/10.3390/en13226022.
DOI: https://doi.org/10.3390/en13226022

Interpretive Summary: Warm season grasses are the most productive plants in the world for generating above ground biomass (e.g. amount of leaves, stems, and seeds). The stems and leaves can be converted to sugars for fermentation to renewable fuels and chemicals. However, processes developed in the lab have resisted commercialization because of the thin profit margins and high capital requirements. ARS researchers are working with a national research consortium that is engineering grasses to accumulate vegetable oil in their stems and leaves. The grasses would be harvested, and the oil recovered while the residual fibers are converted to sugars for fermentation. The oil would generate new revenue when sold either to make jet fuel, green diesel, or for chemicals. However, new technology is required to recover the oil and at the same time preparing the fibers for conversion to sugars. Because the lipid containing plants are still in development, this study used corn germ meal (a corn wet milling coproduct). The corn germ meal was treated under conditions that are favorable for later recovering the sugars using enzymes. Under these conditions, it was shown that the oil becomes concentrated in the processed fibers, can be recovered at good yields, and remains largely intact. Finally, once the oil was removed, the processed fibers made an excellent resource for producing sugars. This is of interest to farmers looking to the future for new crops and large agricultural processors interested in new resources for making sustainable fuels.

Technical Abstract: Engineered energy crops with capability of accumulating vegetative lipids provide a future opportunity for high production of vegetable oil per unit land. However, the low concentration of lipids in current engineered plant biomass samples makes the oil extraction process challenging and expensive. In this study, liquid hot water (LHW) pretreatment was investigated to enrich the solids for oil and increase enzymatic hydrolysis efficiency of such feedstocks. Corn germ meal was chosen as a model feedstock representing lipid producing energy crops. Germ meal was pretreated at 160 and 180 °C for 10 and 15 min at 20 % w/w solids loading. Enzymatic hydrolysis on pretreated solid was performed. After pretreatment, the oil concentration increased by 2.2 to 4.2 fold. The most severe pretreatment condition of LHW, at 180°C for 15 min, gave the maximum oil concentration (9.7%, w/w), the highest TAG content of the extracted oil (71.6%) and the highest conversions of glucose and xylose (99.0% and 32.8%, respectively). This study demonstrates that the optimal pretreatment condition for corn germ meal is 180°C LHW for 15 min. Pretreatment improves lipids recovery from oil bearing biomass with little or no effect on lipid profile.