Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Environmental Engineering and Earth Science

Committee Member

Terry Walker

Committee Member

Yi Zheng

Committee Member

Caye Drapcho

Committee Member

Julia Kerrigan


Lignocellulosic biomass is one of the most abundant natural resources available, though has not been fully exploited as a feedstock for fuel and chemicals. Thermochemical conversions of this biomass face a range of issues as a result of the inorganic elements present in the biomass, thus necessitating a pretreatment to remove such elements. Bioleaching is one promising method to achieve this objective, by utilizing microbial activities to extract and remove the inorganic components from the biomass feedstock.In this research three microbial species including two fungi (Fusarium oxysporum and Aspergillus niger) and one bacterium (Burkholderia fungorum) were selected to pretreat four lignocellulosic feedstocks – switchgrass, corn stover, wheat straw and sorghum. Results demonstrated that among the three microbes, A. niger was the most efficient in removing most elements by 80% after 48 hours, and sorghum was relatively more amenable to bioleaching. With A. niger, the bioleaching with a water to feedstock ratio (v/w) of 25 for 6 h was sufficient to leach K (85%), Cl (90%), Mg (60%), and P (70%) from sorghum. Bioleaching was shown as more efficient than water leaching. Studies on bioleaching mechanism indicated that the acidification resulted from organic acids produced by A. niger during bioleaching might have contributed to the higher leaching efficiency. Following that, the bioleaching process with A. niger was scaled up to be carried out in custom built bioreactors. Three operating parameters were investigated for their effects on leaching efficiency – fungal mass added to each reactor, leaching time, and glucose concentration. Response surface methodology (RSM) was used for the experiment design and model regression. Results showed that after the bioreactor leaching process, the residual ash percentage of the sorghum biomass was significantly lower (3.63±0.19%, mean ± standard deviation) compared with the ash content (4.72±0.13%) after water leaching(p



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