Title page for ETD etd-11112012-190037

Type of Document Master's Thesis
Author Cao, Shuo
Author's Email Address scao2@tigers.lsu.edu
URN etd-11112012-190037
Title Effect of Surfactants on the Pretreatment of Sugarcane Bagasse with Dilute Ammonia
Degree Master of Science (M.S.)
Department Food Science
Advisory Committee
Advisor Name Title
Aita, Giovanna Committee Chair
Finley, John Committee Member
King, Joan Committee Member
  • Enzyme hydrolysis
  • Sugarcane bagasse
  • Dilute ammonia pretreatment
  • Tween 80
  • Non-ionic surfactant
Date of Defense 2012-11-09
Availability unrestricted
Lignocellulosic biomass is composed of cellulose, hemicellulose and lignin which are not readily available for conversion in their native form. It is widely accepted that lignin acts as the “glue” that binds cellulose and hemicellulose, giving rigidity and resistance to lignocellulose. The use of non-ionic surfactants during pretreatment can help alter the structure of lignocellulosic biomass to improve cellulose digestibility and ethanol yields.

Tween 80, Tween 20, PEG 4000, or PEG 6000 was used with ammonium hydroxide for the pretreatment of sugarcane bagasse. The pretreatment was carried out by mixing sugarcane bagasse, ammonium hydroxide (28% v/v) and water at a ratio of 1: 0.5: 20, adding 3% (w/w) surfactant based on the weight of dry biomass, and heating the mixture to 160 °C for 1 h. The final concentration of ammonium hydroxide was 0.65% w/w at 4.7% solids loading. Chemical compositions were determined before and after pretreatment. Fibers were hydrolyzed using commercial enzymes, Spezyme CP and Novozyme 188. Fermentable sugars and ethanol concentrations were analyzed by HPLC. The results indicated that PEG 4000 and Tween 80 gave the highest cellulose digestibilities (62%, 66%) and ethanol yields (73%, 69 %), respectively.

Tween 80 was selected over PEG 4000 because of its low cost. The effect of two concentrations of ammonium hydroxide 0.26% w/w (1: 0.2: 20, biomass: ammonium hydroxide: water ratio) and 0.65% w/w (1: 0.5: 20, biomass: ammonium hydroxide: water ratio), and Tween 80 (1.5%, 3% and 5% w/w, based on the weight of dry biomass) were evaluated during pretreatment at 4.7% solids loading. The greatest lignin removal (37%), cellulose digestibility (66%) and hemicellulose digestibility (43%) were observed at 1: 0.5: 20 ratio supplemented with 3% (w/w) Tween 80. These pretreatment parameters were selected for scale-up experiments at a higher solids loading (10.5%) in a 20 L bioreactor. The greatest lignin removal (55%), cellulose digestibility (72%) and hemicellulose digestibility (57%) were observed with 3% Tween 80-dilute ammonia pretreatment at 1: 0.5: 8 ratio with a final concentration of ammonium hydroxide of 1.47% w/w. Morphological changes in the structure of non-ionic surfactant-dilute ammonia pretreated sugarcane bagasse were observed.

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