Production and recovery of multiple high-value bioproducts from metabolically engineered transgenic sugarcane ‘oilcane’

Bio-based chemicals provide a green and sustainable alternative to petrochemicals. Bioenergy crops have demonstrated their potential for being a sustainable and renewable feedstock for biofuels and various value-added bioproducts. They are well adapted to be grown on non-production farmland and are not expected to impact the food/feed markets. Recently, sugarcane (Saccharum spp. Hybrids) has been genetically modified to hyperaccumulate lipids in vegetative tissues to enhance the energy density of the crop and is referred to as ‘oilcane’. A significant amount of 5-hydroxymethyl furfurals (HMF), furfural and acetic acid produced during valorization of lignocellulosic biomass is considered undesired and ends up in a waste stream. This study transforms the undesired byproducts into valuable coproducts by developing green technologies to coproduce and recover them from oilcane bagasse, along with vegetative lipids and cellulosic sugars. Chemical-free hydrothermal pretreatment conditions were optimized to maximize production of HMF, furfural and acetic acid, without destroying the vegetative lipids or impacting the total yield of cellulosic sugars. Hydrothermal pretreatment at 210 °C for 5 min yielded 2.67 %, 6.91 %, 5.07 %, 2.42 % and 37.82 % (w/w) HMF, furfural, acetic acid, vegetative lipids, and cellulosic sugars, respectively, from oilcane bagasse. Additionally, two-stage nanofiltration was established to recover HMF and furfural from pretreatment liquor. The first nanofiltration step used a Duracid NF membrane that allowed furans and acetic acid to pass through and rejected ~99% sugars. Concentrated cellulosic sugars with significantly reduced inhibitory sugar degradation products were obtained in the retentate as a feedstock for fermentation. The second nanofiltration used a NF90 membrane on the furan and acetic acid enriched permeate recovered from the first nanofiltration step. Furfural was concentrated in the retentate of second nanofiltration while HMF and acetic acid passed into the permeate. The NF90 membrane rejected ~86% furfural. Alternatively, acetic acid obtained in the permeate of second nanofiltration can be retained in the retentate of first nanofiltration and serves as a carbon source for microbial fermentations by adjusting the pH of the feed to shift acetic acid to its deprotonated form. The two-stage nanofiltration using pretreatment liquor that was adjusted to pH 5.5 increased retention of acetic acid by 66% without affecting retention of sugars. The higher retention of acetic acid also enhanced recoveries and purification of HMF and furfural by nanofiltrations. HMF was recovered with significantly reduced organic acids in the permeate of second nanofiltration. The more neutral pH of pretreatment liquor resulted in a higher formic acid concentration in the feed and retentate of the first nanofiltration, which is a drawback. Microbial lipids produced from oleaginous yeasts that accumulate intracellular lipids and are suitable feedstocks for production of biodiesel, a sustainable drop-in fuel alternative to petroleum-based diesel. The oilcane enzymatic hydrolysate prepared from oilcane bagasse was combined with undetoxified pretreatment liquor or retentates of first nanofiltration as fermentation media. Cellulosic sugars in these media were converted to lipids using an oleaginous yeast Rhodotorula toruloides. R. toruloides grew and accumulated 15.44% w/w lipids in the media with 50% v/ oilcane hydrolysate and 25% v/v retentate of first nanofiltration (prepared with unadjusted feed), while no growth was observed when using undetoxified pretreatment liquor. Production of microbial lipids by using sugars from bagasse increases total lipid yield from oilcane. Overall, this study successfully established green technologies to coproduce and recover valuable bio-based platform chemicals (HMF and furfural) and lipids from lignocellulosic biomass. The diversified coproducts increase revenue streams of a biorefinery, which in turn would improve its profitability. A conceptual integrated bioprocessing model that coproduces four valuable products (bio-based HMF, furfural, biodiesel, and crude glycerol) from oilcane in a single run was designed and analyzed. A detailed techno-economic analysis (TEA) and life cycle assessment (LCA) of the integrated biorefinery design was performed under uncertainties for sensitivity analysis using BioSTEAM, a python-based platform. The evaluation results showed that the biorefinery could afford a maximum feedstock purchasing price of $64.47 per MT (median) and produce HMF with a minimum selling price of $7.26 per kg (median), which is ~60% lower than the current market value of HMF. The median global warming potential of HMF was estimated to be 3.61 kg CO2-eq/kg HMF, which was ~38% less than its counterpart, bio-based p-xylene. Diverse coproducts produced at the biorefinery using a transgenic feedstock positively impacted economic feasibility and environmental sustainability.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Agricultural & Biological Engr

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2024

Author dc:creator

• Jia, Yuyao

Contributors dc:contributor

• Singh, Vijay
• Zhao, Huimin
• Guest, Jeremy
• Dien, Bruce S.

• Biobased Hmf
• Lignocellulosic Biomass
• Nanofiltration
• Techno-economic Analysis
• Life Cycle Assessment

Statement dc:rights

• Copyright 2024 Yuyao Jia

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/125748

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F125748