Engineering microorganisms to convert lignin into low molecular weight aromatic derivatives and other value-added products

• Main Author: Lo, Samuel Tat Ming
• Other Authors: Chang Wook, Matthew
• Format: Theses and Dissertations
• Language: English
• Published: 2014
• Subjects: DRNTU::Engineering::Chemical engineering::Biochemical engineering
• Online Access: https://hdl.handle.net/10356/61761
• Institution: Nanyang Technological University

Biological production of high-value chemicals from renewable resources offers an environmentally friendly and sustainable alternative to traditional organic chemical synthesis routes. However, the adoption of this approach in lignocellulosic fermentation is hampered by the low production efficiency and the high costs. Thus, this research aims to boost the utilization of the waste-based lignin-derived hydroxycinnamic acids by targeting biocatalytic cell viability and biorefinery processing costs. Attempts to improve cell viability coupled with reducing material costs include engineering a novel auto-regulatory time-delay expression system that self-regulates enzyme expression via cell-density and hydroxycinnamic acid substrate cues. No costly inducers are needed for this expression system. In addition, with the aim of simplifying downstream processing, biocatalytic host, E. coli was engineered to auto-lyse to release macromolecular products at high cell density / stationary phase. The elimination of the need for the mechanical / chemical / enzymatic treatment of E. coli for product extraction may offer potential cost savings. Lastly, to expedite the bioconversion process of hydroxycinnamic acid, strain engineering was performed on E. coli for improving its tolerance towards high concentration of ferulic acid, a highly abundant hydroxycinnamic acid in nature. As a result of the adaptive evolution, the adapted E. coli is capable of tolerating 9 g/L ferulic acid, up from 4 g/L. These combined findings offer exciting opportunities of utilizing hydroxycinnamic acids for biochemical production.