Publications by authors named "Youngsoon Um"

Lignocellulosic biomass is a promising renewable feedstock for biodegradable plastics like polyhydroxyalkanoates (PHAs). Cupriavidus necator, a versatile microbial host that synthesizes poly(3-hydroxybutyrate) (PHB), the most abundant type of PHA, has been studied to expand its carbon source utilization. Since C.

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Given the urgency of climate change, it is imperative to develop innovative technologies for repurposing CO into value-added products to achieve carbon neutrality. Additionally, repurposing nitrogen-source-derived wastewater streams is crucial, focusing on sustainability rather than conventional nitrogen removal in wastewater treatment plants. In this context, microbial protein (MP) production presents a sustainable and promising approach for transforming recovered low-value resources into high-quality feed and food.

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Polyethylene (PE) exhibits high resistance to degradation, contributing to plastic pollution. PE discarded into the environment is photo-oxidized by sunlight and oxygen. In this study, a key enzyme capable of degrading oxidized PE is reported for the first time.

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Background: Industrial biomanufacturing of value-added products using CO as a carbon source is considered more sustainable, cost-effective and resource-efficient than using common carbohydrate feedstocks. Cupriavidus necator H16 is a representative H-oxidizing lithoautotrophic bacterium that can be utilized to valorize CO into valuable chemicals and has recently gained much attention as a promising platform host for versatile C1-based biomanufacturing. Since this microbial platform is genetically tractable and has a high-flux carbon storage pathway, it has been engineered to produce a variety of valuable compounds from renewable carbon sources.

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As thermoplastic, nontoxic, and biocompatible polyesters, polyhydroxyalkanoates (PHAs) are considered promising biodegradable plastic candidates for diverse applications. Short-chain-length/medium-chain-length (SCL/MCL) PHA copolymers are flexible and versatile PHAs that are typically produced from fatty acids, which are expensive and toxic. Therefore, to achieve the sustainable biosynthesis of SCL/MCL-PHAs from renewable non-fatty acid carbon sources (e.

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Various kinds of plastics have been developed over the past century, vastly improving the quality of life. However, the indiscriminate production and irresponsible management of plastics have led to the accumulation of plastic waste, emerging as a pressing environmental concern. To establish a clean and sustainable plastic economy, plastic recycling becomes imperative to mitigate resource depletion and replace non-eco-friendly processes, such as incineration.

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Article Synopsis
  • The study focuses on the biodegradable copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), emphasizing how its elastomeric properties are influenced by the ratio of 3-hydroxyvalerate (3HV) in the composition.
  • An improved biosynthetic method using the bacterium Cupriavidus necator H16 was developed to enhance 3HV production, involving genetic modifications to key metabolic pathways, leading to a significant increase in PHBV yield and 3HV content.
  • The research found that higher 3HV fractions in PHBV resulted in lower glass transition and melting temperatures, with average molecular weights for the modified PHBV ranging from 20
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Article Synopsis
  • Microbial production of medium chain length fatty acids (MCFAs) from renewable resources is crucial for creating a sustainable chemical industry, highlighting recent advances in this area.
  • The review covers two main pathways for MCFA production, categorizing producers into natural and synthetic types and detailing their characteristics and roles in the process.
  • It also discusses engineering strategies and key enzymes for enhancing MCFA yields, while addressing future challenges in achieving more efficient bio-based production methods.
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This study achieved high production of hexanol via gas fermentation using Clostridium carboxidivorans P7 by extracting hexanol from the fermentation broth. The hexanol extraction efficiency and inhibitory effects on C. carboxidivorans P7 of 2-butyl-1-octanol, hexyl hexanoate and oleyl alcohol were examined, and oleyl alcohol was selected as the extraction solvent.

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Background: A representative hydrogen-oxidizing bacterium Cupriavidus necator H16 has attracted much attention as hosts to recycle carbon dioxide (CO) into a biodegradable polymer, poly(R)-3-hydroxybutyrate (PHB). Although C. necator H16 has been used as a model PHB producer, the PHB production rate from CO is still too low for commercialization.

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, the non-conventional yeast capable of high lipogenesis, is a microbial chassis for producing lipid-based biofuels and chemicals from renewable resources such as lignocellulosic biomass. However, the low tolerance of against furfural, a major inhibitory furan aldehyde derived from the pretreatment processes of lignocellulosic biomass, has restricted the efficient conversion of lignocellulosic hydrolysates. In this study, the furfural tolerance of has been improved by supporting its endogenous detoxification mechanism.

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Article Synopsis
  • The study explores the production of hexanol from syngas using acetogenic bacteria as a sustainable alternative to petroleum-derived hexanol, crucial for chemical synthesis and plastics.
  • Researchers found that lowering the fermentation temperature to 30°C and increasing CO gas content significantly boosted hexanol production from 0.02 to 1.90 g/L, establishing it as the main product for the first time.
  • The introduction of ethanol during fermentation further enhanced hexanol yield, achieving 2.34 g/L, indicating that optimizing gas fermentation conditions and using added ethanol can effectively improve bio-hexanol production.
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Efficient xylose catabolism in engineered enables more economical lignocellulosic biorefinery with improved production yields per unit of biomass. Yet, the product profile of glucose/xylose co-fermenting is mainly limited to bioethanol and a few other chemicals. Here, we introduced an n-butanol-biosynthesis pathway into a glucose/xylose co-fermenting strain (XUSEA) to evaluate its potential on the production of acetyl-CoA derived products.

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Herein, it was unearthed that manganese peroxidase (MnP) from Phanerochaete chrysosporium, a lignin-degrading enzyme, is capable of not only directly decomposing cellulosic components but also boosting cellulase activity. MnP decomposes various cellulosic substrates (carboxymethyl cellulose, cellobiose [CMC], and Avicel®) and produces reducing sugars rather than oxidized sugars such as lactone and ketoaldolase. MnP with Mn in acetate buffer evolves the Mn-acetate complex functioning as a strong oxidant, and the non-specificity of Mn-acetate enables cellulose-decomposition.

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We previously engineered Enterobacter aerogenesfor glucose and xylose co-utilization and 2,3-butanediol production. Here, strain EMY-22 was further engineered to improve the 2,3-butanediol titer, productivity, and yield by reducing the production of byproducts. To reduce succinate production, the budABC operon and galP gene were overexpressed, which increased 2,3-butanediol production.

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Background: Lignocellulosic biorefinery offers economical and sustainable production of fuels and chemicals. , a promising industrial host for biorefinery, has been intensively developed to expand its product profile. However, the sequential and slow conversion of xylose into target products remains one of the main challenges for realizing efficient industrial lignocellulosic biorefinery.

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Several bioprocessing technologies, such as separate hydrolysis and fermentation (SHF), simultaneous saccharification and fermentation (SSF), and consolidated bioprocessing (CBP), have been highlighted to produce bio-based fuels and chemicals from lignocellulosic biomass. Successful CBP, an efficient and economical lignocellulosic biorefinery process compared with other processes, requires microorganisms with sufficient cellulolytic activity and biofuel/chemical-producing ability. Here, we report the complete genome of Paenibacillus sp.

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A brown alga Saccharina japonica and rice straw are attractive feedstock for microbial butyric acid production. However, inefficient fermentation of mannitol (a dominant component in S. japonica) and toxicity of inhibitors in lignocellulosic hydrolysate are limitations.

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Article Synopsis
  • Engineered strains have enhanced biorefinery capabilities, particularly in producing bioethanol and advanced biofuels, but effective use of high-performance xylose-fermenting strains has been limited.
  • This study developed a modified xylose-fermenting strain called XUSE, which efficiently converts xylose into ethanol with a notable yield of 0.43 g/g and can ferment both glucose and xylose simultaneously without glucose inhibition.
  • The genomic analysis of XUSE identified key mutations and gene expression changes that contribute to its improved xylose fermentation, suggesting its potential as a leading platform for lignocellulosic biorefinery applications.
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RNA-guided genome engineering technologies have been developed for the advanced metabolic engineering of microbial cells to enhance production of value-added chemicals in Corynebacterium glutamicum as an industrial host. In this study, the RNA-guided CRISPR interference (CRISPRi) was applied to rapidly identify of unknown genes for native esterase activity in C. glutamicum.

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The recalcitrant structure of lignocellulosic biomass is a major barrier in efficient biomass-to-ethanol bioconversion processes. The combination of feedstock engineering via modification in the lignin synthesis pathway of sugarcane and co-fermentation of xylose and glucose with a recombinant xylose utilizing yeast strain produced 148% more ethanol compared to that of the wild type biomass and control strain. The lignin reduced biomass led to a substantially increased release of fermentable sugars (glucose and xylose).

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For cost-effective lignocellulosic biofuel/chemical production, consolidated bioprocessing (CBP)-enabling microorganisms utilizing cellulose as well as producing biofuel/chemical are required. A novel strain Paenibacillus sp. CAA11 isolated from sediment was found to be not only as a cellulose degrader under both aerobic and strict anaerobic conditions but also as a producer of cellulosic biofuel/chemicals.

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Article Synopsis
  • The study explores using CRISPR interference (CRISPRi) for efficient and cost-effective strain development in microbial cell factories, especially in the bacterium Corynebacterium glutamicum.
  • Researchers developed two-plasmid CRISPRi vectors to successfully repress single and double target genes, leading to significant reductions in mRNA levels and desired changes in cell growth based on different carbon sources.
  • The industrial application demonstrated that targeting citrate synthase improved L-lysine yield by 1.39-fold in the modified bacterial strain compared to its parental version, showcasing CRISPRi's potential for enhancing metabolic engineering.
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Saccharomyces cerevisiae is used for edible purposes, such as human food or as an animal feed supplement. Fatty acids are also beneficial as feed supplements, but S. cerevisiae produces small amounts of fatty acids.

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Direct conversion of carbon dioxide (CO) to value-added chemicals by engineering of cyanobacteria has received attention as a sustainable strategy in food and chemical industries. Herein, Synechococcus elongatus PCC 7942, a model cyanobacterium, was engineered to produce α-farnesene from CO. As a result of the lack of farnesene synthase (FS) activity in the wild-type cyanobacterium, we metabolically engineered S.

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