| Microbial synthesis of chemicals from biobased feedstocks is an alternative to manufacture of materials derived from petroleum or unconventional gases, such as shale gas and coalbed methane. Aromatic diacids, terephthalic acid, isophthalic acid , and phthalic acid, are valuable compounds for the polymers and plasticizers industry. These diacids are currently manufactured via Amoco Mid-Century oxidation of petroleum-derived para-, meta- and ortho-xylenes, respectively; a process not without environmental and economic challenges.;In this work, a semi-synthesis of terephthalic, isophthalic, and phthalic acids is outlined using 2-hydroxymuconic acid as a common synthetic precursor. Recombinant Escherichia coli was utilized combining protocatechuic acid anabolic and catabolic pathways to achieve 1.2 g/L 2-hydroxymuconic acid from D-glucose in fed-batch fermentation. Lewis-acid catalysis was explored in a cycloaddition of 2-hydroxymuconic acid with ethylene to produce terephthalic acid. Cyclization of 2-hydroxymuconic acid afforded 6-carboxy-2-pyrone which was reacted with propiolic acid to afford mixtures of isophthalic and phthalic acids. Propiolic acid from biogas methane and ethylene from bioethanol could maximize the amount of renewable carbon in this semi-synthetic strategy, producing all three petroleum-derived aromatic diacids without the need for Amoco Mid-Century oxidation process.;In an additional research trajectory, the production of kanosamine (3-amino-3-deoxy-D-glucose) is evaluated in fed-batch fermentation of recombinant E. coli. Two biosynthesis pathways are reported in the literature: one native to Bacillus subtilis and the other reported in Amycolatopsis mediterranei and Bacillus pumilus. Genes encoding kanosamine biosynthetic enzymes from B. subtilis, A. mediterranei , and B. pumilus are expressed in Escherichia coli to determine whether heterologous expression results in kanosamine accumulation and if the system can be manipulated to maximize kanosamine production. Recombinant E. coli expressing genes from B. subtilis 168 produces 12.7 +/- 0.6 g/L kanosamine in a 6% mol/mol yield from D-glucose. Kanosamine yields were increased to 18 +/- 1% mol/mol by blocking the Embden-Meyerhoff-Parnas pathway through a mutation in pgi-encoded phosphoglucose isomerase. Enzymes native to A. mediterranei proved to be challenging to efficiently express in E. coli, prompting examination of B. pumilus kanosamine biosynthesis. Expression of B. pumilus SH-B11 genes in E. coli results in 6.3 g/L kanosamine titers in 4.4% mol/mol yield from D-glucose in fed-batch fermentation. In vitro feeding experiments suggest a departure from what is in the literature regarding kanosamine production in Bacillus pumilus. |
