CASCADE BIOREFINERY APPROACHES FOR MORE EFFICIENT CONVERSION OF LIGNOCELLULOSE FEEDSTOCKS TO BIOPRODUCTS
This Ph.D. thesis presents cascade biorefinery strategies to valorize lignocellulosic biomass, particularly rice husk and spent coffee grounds (SCG), into value-added bioproducts. A deacetylation–microwave pretreatment was developed to remove inhibitors and enable microbial conversion of rice husk into poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) by Cupriavidus necator. Uncondensed lignin was also effectively recovered. High-throughput screening of halophilic strains revealed Halomonas neptunia as a promising candidate for converting lignin-derived monomers into PHA. A chemo-enzymatic route was developed to synthesize 2-furoic acid from the hemicellulose fraction via organic acid-catalyzed pretreatment, microwave-assisted dehydration to furfural, and enzymatic oxidation. Lastly, an OrganoCat pretreatment was applied to SCG to extract fermentable sugars, which were utilized by Paraburkholderia sacchari for their growth and biosynthesis of PHB. Overall, this work demonstrates integrated, eco-friendly biorefinery processes for the efficient conversion of all three biomass fractions—cellulose, hemicellulose, and lignin—into bioplastics and furans.
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