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Lee, Nakyeong,Ko, So-Ra,Ahn, Chi-Yong,Oh, Hee-Mock Elsevier 2018 Bioresource technology Vol.258 No.-
<P><B>Abstract</B></P> <P>This study used a single strain <I>Ettlia</I> sp. YC001 and two stages to optimize the production of three materials: lipids, lutein, and β-carotene. In the cultivation stage for lutein production, different temperatures, light qualities, and intensities were applied. The highest biomass was obtained at 35 °C, but the maximum lutein productivity of 6.1 mg/L/d achieved at 25 °C. In the stress stage for lipids and β-carotene production, UV-A and nitrogen starvation were applied. While UV stress increased the chlorophyll-<I>a</I> and β-carotene content. The β-carotene, oleic acid, and lipids significantly increased under nitrogen starvation with a high light intensity of 1200 µmol/m<SUP>2</SUP>/s, plus the <I>Ettlia</I> sp. changed from green to red. The results showed that <I>Ettlia</I> sp. can be an effective microalga for the co-production of lutein, β-carotene, and biodiesel.</P> <P><B>Highlights</B></P> <P> <UL> <LI> <I>Ettlia</I> sp. YC001 produces lutein and β-carotene, along with lipids. </LI> <LI> Two-stage cultivation was adopted for co-production of lipid and carotenoids. </LI> <LI> The highest lutein content was 7.8 mg/g with white light at 25 °C. </LI> <LI> Double stress induced the accumulation of lipids (58.2%) and β-carotene (19.5 mg/g). </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
( Sang-ah Lee ),( Nakyeong Lee ),( Hee-mock Oh ),( Chi-yong Ahn ) 한국미생물생명공학회(구 한국산업미생물학회) 2019 Journal of microbiology and biotechnology Vol.29 No.9
Although chemical oxygen demand (COD) is an important issue for wastewater treatment, COD reduction with microalgae has been less studied compared to nitrogen or phosphorus removal. COD removal is not efficient in conventional wastewater treatment using microalgae, because the algae release organic compounds, thereby finally increasing the COD level. This study focused on enhancing COD removal and meeting the effluent standard for discharge by optimizing sludge inoculation timing, which was an important factor in forming a desirable algae/bacteria consortium for more efficient COD removal and higher biomass productivity. Activated sludge has been added to reduce COD in many studies, but its inoculation was done at the start of cultivation. However, when the sludge was added after 3 days of cultivation, at which point the COD concentration started to increase again, the algal growth and biomass productivity were higher than those of the initial sludge inoculation and control (without sludge). Algal and bacterial cell numbers measured by qPCR were also higher with sludge inoculation at 3 days later. In a semi-continuous cultivation system, a hydraulic retention time of 5 days with sludge inoculation resulted in the highest biomass productivity and N/P removal. This study achieved a further improved COD removal than the conventional microalgal wastewater treatment, by introducing bacteria in activated sludge at optimized timing.
Manganese Transporter Proteins in Salmonella enterica serovar Typhimurium
Ha Nakyeong,Lee Eun-Jin 한국미생물학회 2023 The journal of microbiology Vol.61 No.3
The metal cofactors are essential for the function of many enzymes. The host restricts the metal acquisition of pathogens for their immunity and the pathogens have evolved many ways to obtain metal ions for their survival and growth. Salmonella enterica serovar Typhimurium also needs several metal cofactors for its survival, and manganese has been found to contribute to Salmonella pathogenesis. Manganese helps Salmonella withstand oxidative and nitrosative stresses. In addition, manganese affects glycolysis and the reductive TCA, which leads to the inhibition of energetic and biosynthetic metabolism. Therefore, manganese homeostasis is crucial for full virulence of Salmonella. Here, we summarize the current information about three importers and two exporters of manganese that have been identified in Salmonella. MntH, SitABCD, and ZupT have been shown to participate in manganese uptake. mntH and sitABCD are upregulated by low manganese concentration, oxidative stress, and host NRAMP1 level. mntH also contains a Mn2+- dependent riboswitch in its 5′ UTR. Regulation of zupT expression requires further investigation. MntP and YiiP have been identified as manganese efflux proteins. mntP is transcriptionally activated by MntR at high manganese levels and repressed its activity by MntS at low manganese levels. Regulation of yiiP requires further analysis, but it has been shown that yiiP expression is not dependent on MntS. Besides these five transporters, there might be additional transporters that need to be identified.