Discarded Egg Yolk as an Alternate Source of Poly(3-Hydroxybutyrate-co-3-hydroxyhexanoate)

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Polyhydroxybutyrate (PHB) production from lignocellulosic biomass is economically beneficial. Because lignocellulosic biomass is a mixture rich in glucose and xylose, Escherichia coli , which prefers glucose, needs to overcome glucose repression for efficient biosugar use. To avoid glucose repression, here, we overexpressed a xylose regulator ( xylR ) in an E. coli strain expressing bktB , phaB , and phaC from Cupriavidus necator and evaluated the effect of xylR on PHB production. XylR overexpression increased xylose consumption from 0% to 46.53% and produced 4.45-fold more PHB than the control strain without xylR in a 1% sugar mixture of glucose and xylose (1:1). When the xylR -overexpressed strain was applied to sugars from lignocellulosic biomass, cell growth and PHB production of the strain showed a 4.7-fold increase from the control strain, yielding 2.58 ± 0.02 g/l PHB and 4.43 ± 0.28 g/l dry cell weight in a 1% hydrolysate mixture. XylR overexpression increased the expression of xylose operon genes by up to 1.7-fold. Moreover, the effect of xylR was substantially different in various E. coli strains. Overall, the results showed the effect of xylR overexpression on PHB production in a non-native PHB producer and the possible application of xylR for xylose utilization in E. coli .

Section: Methodsmentioning

confidence: 99%

Validating a Xylose Regulator to Increase Polyhydroxybutyrate Production for Utilizing Mixed Sugars from Lignocellulosic Biomass Using Escherichia coli

Oh,

Lee,

Hwang

et al. 2023

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“…The residual PHB quantity was determined using gas chromatography (GC) as previously described, with slight modifications [ 17 - 20 ]. For analysis, the culture medium was centrifuged at 10,000 × g for 10 min to collect the residual PHB films, followed by a washing process with deionized water to remove cell residue attached to the film.…”

Section: Methodsmentioning

confidence: 99%

Novel Polyhydroxybutyrate-Degrading Activity of the Microbulbifer Genus as Confirmed by Microbulbifer sp. SOL03 from the Marine Environment

Park

Cho

Kim

et al. 2022

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IntroductionPoly(3-hydroxybutyrate) (PHB) is a well-studied bioplastic that can be produced from renewable biomass with physical properties similar to those of petroleum-based plastics [1]. Since PHB accumulates inside microorganisms as a carbon and energy storage compound under unfavorable growth conditions, it can also be degraded into water-soluble monomers, water, and carbon dioxide under carbon-and nitrogen-limiting conditions by microorganisms in a relatively short time compared to that needed for petroleum-based plastics [2]. As the biodegradability of PHB becomes more highly regarded as a great advantage in the industrial field, its replacement of petroleum-based plastics has been increasing.There are several well-known PHB-degrading bacteria that utilize the mechanism of depolymerization for PHB degradation, including Pseudomonas pickettii, Comamonas testosterone, Alcaligenes faecalis, and Cupriavidus necator [3][4][5][6]. However, there are many undiscovered bacteria that can decompose PHB; thus, isolation and application of PHB-degrading bacteria in the disposal of bioplastics is regarded as an effective method of addressing bioplastic wastes and has led to additional studies [7,8].Members of the genus Microbulbifer are gram-negative Gammaproteobacteria found in high-salt environments, with blebs or vesicles on the surface of the cell [9]. There are few species in the Microbulbifer genus that are known as producers of bioactive substances as well as degraders of polysaccharides (Table 1). For example, Microbulbifer Ever since bioplastics were globally introduced to a wide range of industries, the disposal of used products made with bioplastics has become an issue inseparable from their application. Unlike petroleum-based plastics, bioplastics can be completely decomposed into water and carbon dioxide by microorganisms in a relatively short time, which is an advantage. However, there is little information on the specific degraders and accelerating factors for biodegradation. To elucidate a new strain for biodegrading poly-3-hydroxybutyrate (PHB), we screened out one PHB-degrading bacterium, Microbulbifer sp. SOL03, which is the first reported strain from the Microbulbifer genus to show PHB degradation activity, although Microbulbifer species are known to be complex carbohydrate degraders found in high-salt environments. In this study, we evaluated its biodegradability using solid-and liquid-based methods in addition to examining the changes in physical properties throughout the biodegradation process. Furthermore, we established the optimal conditions for biodegradation with respect to temperature, salt concentration, and additional carbon and nitrogen sources; accordingly, a temperature of 37 o C with the addition of 3% NaCl without additional carbon sources, was determined to be optimal. In summary, we found that Microbulbifer sp. SOL03 showed a PHB degradation yield of almost 97% after 10 days. To the best of our knowledge, this is the first study to investigate the potent bioplastic degradation acti...

“…For mild alkaline methanolysis, 0.5 ml methanol, 0.5 ml toluene, and 1 ml 0.3 M methanolic-KOH were added to each sample and incubated at 37°C for 15 min. A 2 ml aliquot of n-hexane/chloroform (4:1 v/v), 1 ml 1 M acetic acid, 2 ml Milli Q water was added, and the upper hexane layer was removed and concentrated under compressed N2, and fatty acids were re-solubilized with chloroform [ 34 , 35 ]. Any remaining water was removed by Na 2 SO 4 and analyzed using the GC–MS system (Perkin Elmer, USA) equipped with a fused silica capillary column (Elite-5 ms, 30 m, 0.25 mm, i.d.…”

Section: Methodsmentioning

confidence: 99%

Comparative Study of the Difference in Behavior of the Accessory Gene Regulator (Agr) in USA300 and USA400 Community-Associated Methicillin-Resistant Staphylococcus aureus (CA-MRSA)

Lee

Song

Lee

et al. 2021

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Community-associated Methicillin-Resistant Staphylococcus aureus (CA-MRSA) is notorious as a leading cause of soft tissue infections. Despite several studies on the Agr regulator, the mechanisms of action of Agr on the virulence factors in different strains are still unknown. To reveal the role of Agr in different CA-MRSA, we investigated the LACΔagr mutant and the MW2Δagr mutant by comparing LAC (USA300), MW2 (USA400), and Δagr mutants. The changes of Δagr mutants in sensitivity to oxacillin and several virulence factors such as biofilm formation, pigmentation, motility, and membrane properties were monitored. LACΔagr and MW2Δagr mutants showed different oxacillin sensitivity and biofilm formation compared to the LAC and MW2 strains.Regardless of the strain, the motility was reduced in Δagr mutants. And there was an increase in the long chain fatty acid in phospholipid fatty acid composition of Δagr mutants. Other properties such as biofilm formation, pigmentation, motility, and membrane properties were different in both Δagr mutants. The Agr regulator may have a common role like the control of motility and straindependent roles such as antibiotic resistance, biofilm formation, change of membrane, and pigment production. It does not seem easy to control all MRSA by targeting the Agr regulator only as it showed strain-dependent behaviors.