Date of Award
2023
Document Type
Open Access Master's Report
Degree Name
Master of Science in Biological Sciences (MS)
Administrative Home Department
Department of Biological Sciences
Advisor 1
Rebecca Garlock Ong
Advisor 2
Chandrashekhar P. Joshi
Committee Member 1
Carsten Külheim
Abstract
Woody biomass, particularly poplar, is a sought-after feedstock for lignocellulosic biofuels because of its year-round availability and high productivity. Because of cell wall components like lignin, poplar is inherently resistant to enzymatic saccharification. The experiment aims to determine whether the controlled overexpression of laccase genes alters the biomass composition and whether it can create poplar that is more digestible than the wildtype.
Three sets of transgenic poplar (Populus tremula x alba) samples were evaluated: laccase 18, laccase 27, and STTM. Laccase 18 samples, an target of miRNA397a was overexpressed along with Laccase 27. Short Tandem target Mimic (STTM) technology was adopted to block miRNA397a expression so it will not control laccase expression. Small scale compositional analysis was carried out on the transgenic and wild type poplar, consisting of water and ethanol extraction, followed by acid hydrolysis to measure the lignin and polysaccharide content. Alkaline pretreatment was carried at 3% solids loading and 10mL of 62.5 mM NaOH to make biomass more accessible to enzymatic hydrolysis. The samples were washed three times and dried overnight to determine the pretreatment mass loss. The pretreatment liquor was evaluated for glucose and xylose content using HPLC. Enzymatic hydrolysis was performed on the pretreated biomass at 3% solids loading to convert glucan and xylan to fermentable sugars. The set temperature was 50°C, and the stirring speed was 250 RPM. Samples were collected for HPLC analysis at 24 hours and 72 hours.
When the composition of the laccase 27, laccase 18, and STTM samples were examined, there were lines among all three transgenic modifications that had less lignin than the wild type (control) type samples. Following 72 hours of enzymatic hydrolysis, transgenic samples showed higher glucose release compared to wild type samples, indicating that the transgenic poplar is more digestible than the wild type.
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License
Recommended Citation
Arunima, Fnu, "CHANGES IN POPLAR DIGESTIBILITY DUE TO OVEREXPRESSION OF LACCASE GENES", Open Access Master's Report, Michigan Technological University, 2023.