Lignocellulosic Syrup Production from Energy Cane Bagasse and Fumaric Acid Fermentation

Abstract

Lignocellulosic syrup from dilute ammonia pretreated energy cane bagasse is a promising fermentable sugar feedstock that can improve the logistics associated with long-distance transportation, long-time storage, and year-round supply of lignocellulosic biomass to processing industries. However, non-sugar compounds such as organic acids, furans and phenolic compounds formed during pretreatment can have negative effects on downstream processes such as fermentation. This dissertation focused on addressing challenges associated with the bioconversion of energy cane bagasse to syrup and its fermentation to fumaric acid. The first goal (Chapter 2) was to evaluate the removal of non-sugar compounds with minimal sugar losses from dilute ammonia pretreated energy cane bagasse enzymatic hydrolysate using the cationic flocculants polyethylenimine (PEI) and poly-diallyldimethylammonium chloride (pDADMAC). Optimum conditions for both PEI and pDADMAC were 15 g/L dose at unadjusted hydrolysate pH of 4.5. At these conditions, PEI outperformed pDADMAC by having greater adsorption efficiencies towards non-sugar compounds with minimal sugar losses. PEI removed 43% organic acids, 100% furans and 73% total phenolic compounds with less than 10% total fermentable sugar losses. However, recycling of PEI and recovery of adsorbed non-sugar compounds are not recommended for more than two cycles. The second goal (Chapter 3) was to optimize activated carbon (AC, powdered and granular) detoxification of dilute ammonia pretreated energy cane bagasse hydrolysate via Response Surface Methodology. Optimum conditions for powdered AC were 9.21% (w/w) dose, at pH 1.96 for 10 min. Optimum conditions for granular AC were 12.64% (w/w) dose, at pH 1.91 for 51.60 min. At optimum conditions, approximately 73% organic acids, 95% furans and 99% total phenolic compounds were removed by AC treatment with less than 10% fermentable sugar losses. The last goal (Chapter 4) evaluated the use of AC treated lignocellulosic syrup as the carbon source for fumaric acid fermentation by Rhizopus oryzae ATCC® 20344TM. Fumaric acid is a building block chemical that can be potentially manufactured using renewable lignocellulosic biomass and can serve as the raw material in the production of polymer resins, plasticizers, esters, and inks. Fumaric acid production was 34.20 g/L, with a yield of 0.43 g/g and a productivity of 0.24 g/L/h.