Feedstocks-to-Fuels Pipeline Demonstration: End-to-End Process Synthesis
Shivali Banerjee1,2* (email@example.com), Narendra Naik Deshavath1,2, Shraddha Maitra1,2, Somesh Mishra2, Fredy Altpeter1,3, John Shanklin1,4, Erik J. Sacks2, Bruce S. Dien1,5, Huimin Zhao2, Vijay Singh1,2
1Center for Advanced Bioenergy and Bioproducts Innovation (CABBI); 2University of Illinois Urbana–Champaign; 3University of Florida; 4Brookhaven National Laboratory; and 5National Center for Agricultural Utilization Research (NCAUR), Agricultural Research Service (ARS), United States Department of Agriculture (USDA), Peoria, IL
One goal of the “Feedstocks-to-Fuels Pipeline” project was to demonstrate pilot- scale processing of CABBI feedstocks, namely genetically modified sugarcane (oilcane) and Miscanthus x giganteus for the recovery of vegetative lipids, microbial lipids, succinic acid, and anthocyanins as the main products. Overall, this work on end-to-end process synthesis tests the performance of the CABBI feedstocks, the processing methods, and the yeasts engineered to produce bioproducts at an industrially relevant scale using the Integrated Bioprocessing Research Laboratory identifies technology gaps and develops enabling technologies.
The Feedstocks-to-Fuels pipeline synthesizes advances in feedstocks, bioprocessing technology, and engineered yeasts. The deconstruction of the CABBI feedstocks is the most crucial step in recovering “in planta” products such as oil, waxes, sugars, and pigments. The pilot scale processing of CABBI feedstocks, such as oilcane and purple-stemmed Miscanthus x giganteus, involves the development of biomass deconstruction strategies followed by their conversion into value-added products. Oilcane is produced by the metabolic engineering of sugarcane to accumulate lipids in vegetative tissues (Parajuli et al. 2020). The high biomass productivity of this transgenic bioenergy crop holds the potential to produce more oil per hectare of cultivated land than soybean (Huang et al. 2016). The vegetative lipids present in oilcane have the potential for biodiesel production while the oilcane juice, rich in sugars, can be used for the production of value-added biochemicals.
Oilcane stems were received from the University of Florida and were processed at Integrated Bioprocess Research Laboratory. About 218 kg of juice and 230 kg of wet bagasse were recovered by processing 466 kg of oilcane stems. The oilcane juice was used to produce succinic acid using a novel metabolically engineered Issatchenkia orientialis at an acidic pH of 3 and achieved a 54 g/L titer. In the downstream processing, 63.9% succinic acid was recovered from the fermentation broth with 98.5% purity through filtration, followed by decolorization and crystallization. The processed oilcane bagasse was pretreated through a continuous pilot-scale hydrothermal process at 50% (w/w) solids followed by mechanical refining (HMR) for the deconstruction of the lignocellulosic network. Fed-batch enzymatic hydrolysis of pretreated bagasse was performed to achieve industrially relevant cellulosic sugar concentrations. Processing with HMR did not incur any changes to the in situ lipid profile in the oilcane bagasse and gives optimal recovery of lignocellulosic sugars for conversion to microbial lipids. The major fraction of vegetative lipids were thus recovered from the biomass residue following enzymatic saccharification of the pretreated bagasse (Maitra et al. 2022).
Purple-stemmed Miscanthus x giganteus is another CABBI feedstock and is known for its potential to accumulate natural colorants namely anthocyanins. The overall yield of anthocyanins recovered per unit area is significant due to the high productivity of this bioenergy crop (Banerjee et al. 2023).
Preliminary studies showed that hydrothermal pretreatment of miscanthus could be used as a green approach to recover more than 90% of the total anthocyanins as an additional product stream and also enhanced the enzymatic digestibility of the biomass (Banerjee et al. 2022). For pilot-scale demonstration, 50 kg of purple-stemmed Miscanthus x giganteus, grown at the Energy Farms at the University of Illinois, was processed through a continuous pilot-scale hydrothermal pretreatment at 50% (w/w) solids. The pretreated biomass was further subjected to disc milling. The pretreatment led to a recovery of 94.3% w/w of the total anthocyanins present in miscanthus and also improved the enzymatic digestibility of cellulose leading to a 2.1-fold increase in the overall recovery of glucose. The cellulosic sugars thus obtained were converted into microbial lipids using an oleaginous yeast strain, which are a potential feedstock for biodiesel production.
Overall, the Feedstocks-to-Fuel pipeline successfully demonstrated the potential of two CABBI feedstocks, namely oilcane and purple-stemmed miscanthus. The valorization products were vegetative and microbial lipids for biofuel production along with the production of succinic acid and anthocyanins as additional value-added product streams.
Parajuli, S., et al. 2020. “Towards Oilcane: Engineering Hyperaccumulation of Triacylglycerol into Sugarcane Stems,” GCB Bioenergy 12, 476–490.
Huang, H., et al. 2016. “Techno-Economic Analysis of Biodiesel and Ethanol Co- production from Lipid-Producing Sugarcane,” Biofuels, Bioprod. Biorefining 10, 299–315.
Maitra, S., et al. 2022. “Bioprocessing, Recovery, and Mass Balance of Vegetative Lipids from Metabolically Engineered “Oilcane” Demonstrates Its Potential as an Alternative Feedstock for Drop-In Fuel Production,” ACS Sustain. Chem. Eng. 10, 16833−44.
Banerjee, S., et al. 2023. “Bioenergy Crops as Alternative Feedstocks for Recovery of Anthocyanins: A Review,” Environ. Technol. Innov. 29, 102977.
Banerjee, S., et al. 2022. “Valorization of Miscanthus x giganteus for Sustainable Recovery of Anthocyanins and Enhanced Production of Sugars,” J. Clean. Prod. 369, 133508.