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1.
Int J Pediatr Otorhinolaryngol ; 153: 111008, 2022 Feb.
Article in English | MEDLINE | ID: mdl-34986444

ABSTRACT

OBJECTIVES: Pediatric esophageal button battery (BB) injury occurs rapidly and continues to be a significant source of morbidity and mortality. Unfortunately, a BB that no longer supplies power to a device can still have enough residual voltage to cause injury within the body. Development of additional prevention strategies for consumers may reduce esophageal injury risk. METHODS: In this study, 24 commercially available button batteries (BBs) were horizontally and vertically wrapped (2 layers, full circumferential coverage, 90° apart) with 6 different types of common household tapes (Scotch®/clear, Scotch®/Magic, masking tape, packing tape/clear, packing tape/brown, black electrical tape) and left at room temperature for 30 days. In addition, 6 of the CR2032 batteries covered with each type of tape were placed in a cadaveric piglet esophageal model for a 4-h period and then compared to controls without tape for tissue pH changes and visible tissue injury. RESULTS: None of the tape-wrapped batteries showed voltage changes nor presented any hazard stemming from BB ingestion. All 6 tape covered batteries placed in the cadaveric piglet esophageal tissue model demonstrated no visible tissue injury and no change in tissue pH in contrast to the controls. Review of BB packaging language from various brands of commercially available CR2032 batteries showed that none had specific disposal recommendations. CONCLUSION: Both BB and electronics manufacturers should consider instructing the use of common household tape options to cover these BB immediately after removal from a device for either recycling or disposal. Such precautions may help to reduce related ingestion injuries in children.


Subject(s)
Foreign Bodies , Animals , Child , Electric Power Supplies , Esophagus , Family Characteristics , Foreign Bodies/prevention & control , Humans , Risk Reduction Behavior , Swine
2.
Metab Eng ; 55: 92-101, 2019 09.
Article in English | MEDLINE | ID: mdl-31226347

ABSTRACT

Common strategies for conversion of lignocellulosic biomass to chemical products center on deconstructing biomass polymers into fermentable sugars. Here, we demonstrate an alternative strategy, a growth-coupled, high-yield bioconversion, by feeding cells a non-sugar substrate, by-passing central metabolism, and linking a key metabolic step to generation of acetyl-CoA that is required for biomass and energy generation. Specifically, we converted levulinic acid (LA), an established degradation product of lignocellulosic biomass, to butanone (a.k.a. methyl-ethyl ketone - MEK), a widely used industrial solvent. Our strategy combines a catabolic pathway from Pseudomonas putida that enables conversion of LA to 3-ketovaleryl-CoA, a CoA transferase that generates 3-ketovalerate and acetyl-CoA, and a decarboxylase that generates 2-butanone. By removing the ability of E. coli to consume LA and supplying excess acetate as a carbon source, we built a strain of E. coli that could convert LA to butanone at high yields, but at the cost of significant acetate consumption. Using flux balance analysis as a guide, we built a strain of E. coli that linked acetate assimilation to production of butanone. This strain was capable of complete bioconversion of LA to butanone with a reduced acetate requirement and increased specific productivity. To demonstrate the bioconversion on real world feedstocks, we produced LA from furfuryl alcohol, a compound readily obtained from biomass. These LA feedstocks were found to contain inhibitors that prevented cell growth and bioconversion of LA to butanone. We used a combination of column chromatography and activated carbon to remove the toxic compounds from the feedstock, resulting in LA that could be completely converted to butanone. This work motivates continued collaboration between chemical and biological catalysis researchers to explore alternative conversion pathways and the technical hurdles that prevent their rapid deployment.


Subject(s)
Butanones/metabolism , Escherichia coli , Levulinic Acids/metabolism , Microorganisms, Genetically-Modified , Bacterial Proteins/genetics , Bacterial Proteins/metabolism , Escherichia coli/genetics , Escherichia coli/metabolism , Microorganisms, Genetically-Modified/genetics , Microorganisms, Genetically-Modified/metabolism , Pseudomonas putida/enzymology , Pseudomonas putida/genetics
3.
Metab Eng ; 48: 63-71, 2018 07.
Article in English | MEDLINE | ID: mdl-29807110

ABSTRACT

In this report, we identify the relevant factors to increase production of medium chain n-alcohols through an expanded view of the reverse ß-oxidation pathway. We began by creating a base strain capable of producing medium chain n-alcohols from glucose using a redox-balanced and growth-coupled metabolic engineering strategy. By dividing the heterologous enzymes in the pathway into different modules, we were able to identify and evaluate homologs of each enzyme within the pathway and identify several capable of enhancing medium chain alcohol titers and/or selectivity. In general, the identity of the trans-2-enoyl-CoA reductase (TER) and the direct overexpression of the thiolase (FadA) and ß-hydroxy-acyl-CoA reductase (FadB) improved alcohol titer and the identity of the FadBA complex influenced the dominant chain length. Next, we linked the anaerobically induced VHb promoter from Vitreoscilla hemoglobin to each gene to remove the need for chemical inducers and ensure robust expression. The highest performing strain with the autoinduced reverse ß-oxidation pathway produced n-alcohols at titers of 1.8 g/L with an apparent molar yield of 0.2 on glucose consumed in rich medium (52% of theoretical yield).


Subject(s)
Escherichia coli K12 , Fatty Alcohols/metabolism , Metabolic Engineering , Anaerobiosis/genetics , Bacterial Proteins/genetics , Escherichia coli K12/genetics , Escherichia coli K12/metabolism , Escherichia coli Proteins/biosynthesis , Escherichia coli Proteins/genetics , Gene Expression , Oxidation-Reduction , Oxidoreductases/biosynthesis , Oxidoreductases/genetics , Promoter Regions, Genetic , Truncated Hemoglobins/genetics , Vitreoscilla/genetics
4.
Metab Eng Commun ; 5: 78-83, 2017 Dec.
Article in English | MEDLINE | ID: mdl-29188187

ABSTRACT

Escherichia coli strain LS5218 is a useful host for the production of fatty acid derived products, but the genetics underlying this utility have not been fully investigated. Here, we report the genome sequence of LS5218 and a list of large mutations and single nucleotide permutations (SNPs) relative to E. coli K-12 strain MG1655. We discuss how genetic differences may affect the physiological differences between LS5218 and MG1655. We find that LS5218 is more closely related to E. coli strain NCM3722 and suspect that small genetic differences between K-12 derived strains may have a significant impact on metabolic engineering efforts.

5.
Nat Microbiol ; 2(12): 1624-1634, 2017 Dec.
Article in English | MEDLINE | ID: mdl-28947739

ABSTRACT

Microorganisms can catabolize a wide range of organic compounds and therefore have the potential to perform many industrially relevant bioconversions. One barrier to realizing the potential of biorefining strategies lies in our incomplete knowledge of metabolic pathways, including those that can be used to assimilate naturally abundant or easily generated feedstocks. For instance, levulinic acid (LA) is a carbon source that is readily obtainable as a dehydration product of lignocellulosic biomass and can serve as the sole carbon source for some bacteria. Yet, the genetics and structure of LA catabolism have remained unknown. Here, we report the identification and characterization of a seven-gene operon that enables LA catabolism in Pseudomonas putida KT2440. When the pathway was reconstituted with purified proteins, we observed the formation of four acyl-CoA intermediates, including a unique 4-phosphovaleryl-CoA and the previously observed 3-hydroxyvaleryl-CoA product. Using adaptive evolution, we obtained a mutant of Escherichia coli LS5218 with functional deletions of fadE and atoC that was capable of robust growth on LA when it expressed the five enzymes from the P. putida operon. This discovery will enable more efficient use of biomass hydrolysates and metabolic engineering to develop bioconversions using LA as a feedstock.


Subject(s)
Bacteria/enzymology , Bacteria/genetics , Genes, Bacterial/genetics , Levulinic Acids/metabolism , Metabolic Networks and Pathways/genetics , Bacteria/metabolism , Bacterial Proteins/genetics , Base Sequence , Biomass , CRISPR-Cas Systems/genetics , Carbon/metabolism , DNA Transposable Elements , Escherichia coli/genetics , Escherichia coli/growth & development , Escherichia coli/metabolism , Gene Expression Regulation, Bacterial , Gene Knockdown Techniques , Levulinic Acids/chemistry , Metabolic Engineering , Operon/genetics , Propionates/metabolism , Pseudomonas putida/enzymology , Pseudomonas putida/genetics , Pseudomonas putida/metabolism
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