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Papers by Diane Chauliac

Proceedings of the National Academy of Sciences of the United States of America, Apr 9, 2018

Methane can be converted to triose dihydroxyacetone (DHA) by chemical processes with formaldehyde... more Methane can be converted to triose dihydroxyacetone (DHA) by chemical processes with formaldehyde as an intermediate. Carbon dioxide, a by-product of various industries including ethanol/ butanol biorefineries, can also be converted to formaldehyde and then to DHA. DHA, upon entry into a cell and phosphorylation to DHA-3-phosphate, enters the glycolytic pathway and can be fermented to any one of several products. However, DHA is inhibitory to microbes due to its chemical interaction with cellular components. Fermentation of DHA to D-lactate by Escherichia coli strain TG113 was inefficient, and growth was inhibited by 30 g•L −1 DHA. An ATP-dependent DHA kinase from Klebsiella oxytoca (pDC117d) permitted growth of strain TG113 in a medium with 30 g•L −1 DHA, and in a fed-batch fermentation the D-lactate titer of TG113(pDC117d) was 580 ± 21 mM at a yield of 0.92 g•g −1 DHA fermented. Klebsiella variicola strain LW225, with a higher glucose flux than E. coli, produced 811 ± 26 mM D-lactic acid at an average volumetric productivity of 2.0 g −1 •L −1 •h −1. Fermentation of DHA required a balance between transport of the triose and utilization by the microorganism. Using other engineered E. coli strains, we also fermented DHA to succinic acid and ethanol, demonstrating the potential of converting CH 4 and CO 2 to value-added chemicals and fuels by a combination of chemical/biological processes. dihydroxyacetone | fermentation | methane | lactic acid | ethanol

Journal of Polymers and The Environment, Mar 19, 2020

Polylactic acid polymer (PLA) produced from renewable resources can be recycled at the end of lif... more Polylactic acid polymer (PLA) produced from renewable resources can be recycled at the end of life to constituent monomer, optically pure lactic acid (LA), by a combination of chemical and biological processes. Efficient application of this closed loop of LA-PLA plastics-LA can minimize accumulation of plastics waste that pollute land and oceans. Temperaturedependent hydrolysis of PLA in water to LA follows apparent first order decay kinetics after a short lag. A modified Gompertz equation can explain the overall hydrolysis process. Alkali increased the rate of hydrolysis of PLA and reduced the length of lag period compared to water alone. The stoichiometry of base added to LA released was 1.0. The highest lactic acid yield was 0.95 g g −1 of PLA. d-LA in the syrup obtained after hydrolysis of PLA-plastics was removed using an engineered Escherichia coli to produce a l-LA syrup with an optical purity ≥ 99%. These results show that thermochemical hydrolysis of PLA-based plastics to LA with optimum amount of base followed by bio-based purification to l-LA is an effective method of recycling PLA-plastics for reuse.

Biotechnology Letters, Aug 14, 2015

Objective A bio-based process is appealing for purification of L-lactic acid, the major enantiome... more Objective A bio-based process is appealing for purification of L-lactic acid, the major enantiomer of polylactic acid syrup, generated by thermochemical processes at the end of life of PLA-based plastics, from its chiral impurity, D-lactic acid, before reuse. Results Polylactic acid (PLA), a renewable alternative to petroleum-derived plastics, contains a mixture of Land D-lactic acid (LA) isomers with the L-isomer dominating (up to 95 %). A novel bio-based process was developed to produce chirally pure L-LA from syrup produced during recycling of PLA-plastics. This process utilizes an engineered Escherichia coli (strain DC1001) containing novel gene deletions (lld, ykg) that eliminated the oxidative metabolism of L-lactate, leaving the membrane-bound D-lactate dehydrogenases to selectively metabolize the D-isomer. Strain DC1001 removed 8.7 g D-lactate l-1 from a PLA-syrup containing 135 g total lactic acid l-1 in 24 h. Average rates of removal of D-lactic acid were 0.25 g D-lactate h-1 (g cell dry weight)-1 and 0.36 g D-lactate l-1 h-1. Conclusion Bio-based purification of PLA-syrup utilizing E. coli strain DC1001 is an attractive process step during recycling of PLA-plastics. This selective oxidation process can also be used to remove chiral contamination of L-lactate in medical applications.

Biotechnology and Bioengineering, Oct 30, 2017

Poly lactic acid (PLA) based plastics is renewable, bio-based, and biodegradable. Although presen... more Poly lactic acid (PLA) based plastics is renewable, bio-based, and biodegradable. Although present day PLA is composed of mainly L-LA, an L- and D- LA copolymer is expected to improve the quality of PLA and expand its use. To increase the number of thermotolerant microbial biocatalysts that produce D-LA, a derivative of Bacillus subtilis strain 168 that grows at 50°C was metabolically engineered. Since B. subtilis lacks a gene encoding D-lactate dehydrogenase (ldhA), five heterologous ldhA genes (B. coagulans ldhA and gldA101, and ldhA from three Lactobacillus delbrueckii) were evaluated. Corresponding D-LDHs were purified and biochemically characterized. Among these, D-LDH from L. delbrueckii subspecies bulgaricus supported the highest D-LA titer (about 1M) and productivity (2 g h(-1) g cells(-1) ) at 37°C (B. subtilis strain DA12). The D-LA titer at 48°C was about 0.6 M at a yield of 0.99 (g D-LA g(-1) glucose consumed). Strain DA12 also fermented glucose at 48°C in mineral salts medium to lactate at a yield of 0.89 g g(-1) glucose and the D-lactate titer was 180 ± 4.5 mM. These results demonstrate the potential of B. subtilis as a platform organism for metabolic engineering for production of chemicals at 48°C that could minimize process cost.

Protein Science, Oct 24, 2020

This is the author manuscript accepted for publication and has undergone full peer review but has... more This is the author manuscript accepted for publication and has undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as

Additional file 1: Table S1. E. coli strains constructed and used in this study. Table S2. E. col... more Additional file 1: Table S1. E. coli strains constructed and used in this study. Table S2. E. coli plasmids constructed and used in this study.

Background Several anaerobic bacteria produce butyric acid, a commodity chemical with use in chem... more Background Several anaerobic bacteria produce butyric acid, a commodity chemical with use in chemical, pharmaceutical, food and feed industries, using complex media with acetate as a co-product. Butyrate titer of various recombinant Escherichia coli did not exceed 10 g l−1 in batch fermentations in any of the media tested. Results A recombinant E. coli (strain LW393) that produced butyrate as the major fermentation product was constructed with genes from E. coli, Clostridium acetobutylicum and Treponema denticola. Strain LW393 produced 323 ± 6 mM (28.4 ± 0.4 g l−1) butyric acid in batch fermentations in mineral salt medium with glucose as C source at a yield of 0.37 ± 0.01 g (g glucose consumed)−1. Butyrate accounted for 90% of the total products produced by the culture. Supplementing this medium with yeast extract further increased butyric acid titer to 375 ± 4 mM. Average volumetric productivity of butyrate with xylose as C source was 0.89 ± 0.07 g l−1 h−1. Conclusions The butyrat...

PANGEA: pipeline for analysis of next generation amplicons

Protein Science, 2020

During adaptive metabolic evolution a native glycerol dehydrogenase (GDH) acquired a d‐lactate de... more During adaptive metabolic evolution a native glycerol dehydrogenase (GDH) acquired a d‐lactate dehydrogenase (LDH) activity. Two active‐site amino acid changes were detected in the altered protein. Biochemical studies along with comparative structure analysis using an X‐ray crystallographic structure model of the protein with the two different amino acids allowed prediction of pyruvate binding into the active site. We propose that the F245S alteration increased the capacity of the glycerol binding site and facilitated hydrogen bonding between the S245 γ‐O and the C1 carboxylate of pyruvate. To our knowledge, this is the first GDH to gain LDH activity due to an active site amino acid change, a desired result of in vivo enzyme evolution.

Journal of Polymers and the Environment, 2020

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Proceedings of the National Academy of Sciences of the United States of America, Apr 24, 2018

Biotechnology Letters, 2015

The ISME Journal, 2010

High-throughput DNA sequencing can identify organisms and describe population structures in many ... more High-throughput DNA sequencing can identify organisms and describe population structures in many environmental and clinical samples. Current technologies generate millions of reads in a single run, requiring extensive computational strategies to organize, analyze and interpret those sequences. A series of bioinformatics tools for high-throughput sequencing analysis, including preprocessing, clustering, database matching and classification, have been compiled into a pipeline called PANGEA. The PANGEA pipeline was written in Perl and can be run on Mac OSX, Windows or Linux. With PANGEA, sequences obtained directly from the sequencer can be processed quickly to provide the files needed for sequence identification by BLAST and for comparison of microbial communities. Two different sets of bacterial 16S rRNA sequences were used to show the efficiency of this workflow. The first set of 16S rRNA sequences is derived from various soils from Hawaii Volcanoes National Park. The second set is derived from stool samples collected from diabetesresistant and diabetes-prone rats. The workflow described here allows the investigator to quickly assess libraries of sequences on personal computers with customized databases. PANGEA is provided for users as individual scripts for each step in the process or as a single script where all processes, except the v 2 step, are joined into one program called the 'backbone'.

Bioresource Technology, 2013

h i g h l i g h t s " Thermophilic, non-agitated and agitated digestion showed marked differences... more h i g h l i g h t s " Thermophilic, non-agitated and agitated digestion showed marked differences in performance. " Methane yield from agitated digester was 74% of that from non-agitated digester. " Non-agitated digester produced methane at twice the rate of agitated digester. " Performance of agitated digester inoculum quickly improved when used in non-agitated digester. " Agitated digester exhibited a high abundance of hydrogen-producing microbial community.