Date of Award
4-13-2016
Document Type
Dissertation
Degree Name
Molecular Biosciences, Ph.D.
First Advisor
Brett Savary
Committee Members
Carole Cramer; Gregory Phillips; Jianfeng Xu; Randall Cameron
Call Number
LD 251 .A566d 2016 T56
Abstract
Sugar beets (Beta vulgaris L.) are the major source of food-grade sucrose produced in the United States. Beet sugar production is energy intensive and generates high greenhouse gas emissions. Up to a third of the energy consumed in a processing factory is used to dry beet pulp, the pectin-rich biomass left after sucrose extraction. Previous studies investigated the thermally tolerant pectin methylesterase (TT-PME; EC 3.1.1.11) for its role in degrading citrus juice quality and for modifying pectin for food applications. My research investigated TT-PME for an innovative application in processing pectin-rich biomass. This addressed the overall hypothesis that selective action by thermally tolerant pectinases such as TT-PME, can modify cell wall structure to reduce energy demands for drying beet pulp. The Specific Aims were to: 1) evaluate pectinase treatment of sugar beet pulp for improved processing properties, 2) generate selective antibodies for differentially identifying recombinant TT-PME expressed in plant tissues, and 3) determine functionality of TT-PME’s pre and PRO regions for recombinant expression in planta by transient expression. To test the hypothesis, I developed a new assay to quantify water binding by beet pulp following enzyme treatments. Thus, I determined PME treatment reduced water binding in beet pulp by 25% through a calcium-mediated mechanism. Additional treatments with arabinanase (E.C. 3.2.1.99) showed no effect on water separation. These results provided proof of concept that TT-PME expression in sugar beets may confer a processing benefit by facilitating water separation from beet pulp. For TT-PME expression studies in transgenic plants, antibodies for TT-PME were produced from a sequence-specific peptide. These antibodies differentially detected TT-PME from other plant PMEs. Towards developing an expression strategy for sugar beets, TT-PME structural constructs were tested in the Nicotiana benthamiana transient expression system. TT-PME’s native signal peptide yielded high expression levels, equal to the well-established patatin signal peptide. Furthermore, I demonstrated that TT-PME must be expressed with its PRO region. These results will direct future TT-PME expression studies in biotech beets to deliver the benefit of reduced processing energy demands. These TT-PME expressing biotech beets will improve economic profitability while reducing the carbon footprint of beet sugar factories.
Rights Management
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
Tovar, Jose Carlos, "Development Of the Thermally Tolerant Pectin Methylesterase for an Innovative Application in Biomass Processing" (2016). Student Theses and Dissertations. 625.
https://arch.astate.edu/all-etd/625
