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ABSTRACT: Spent sulfidic caustic was applied to sulfur utilizing autotrophic denitrification as the simultaneous source of electron
donor and alkalinity. The two experiment set-up of upflow anoxic hybrid growth reactor (UAHGR) and upflow anoxic suspended
growth reactor (UASGR) was adopted and nitrate removals were similar in both reactors. Approximately 90% of the initial nitrate
was denitrified at nitrate loading rate of 0.15∼0.40 kgNO3
−/m3·d. The experimental stoichiometric ratio of sulfate production to nitrate removal was ranged from 1.5 to 2.1 mgSO4
2−/mgNO3
−. During the operation period, denaturing gradient gel electrophoresis (DGGE) analysis of polymerase chain reaction (PCR)-amplified
16S rDNA fragments for the sludge sample of both reactors showed the change of microbial communities. Thiobacillus denitrificans-like microorganism occupied 28.5% (18 clones) of the 63 clones by cloning the PCR products from the sludge sample of UAHGR.
Acidovorax avenae, which can reduce nitrate to nitrogen gas while oxidizing phenol (heterotrophic denitrifier), was also found in 7 clones
(11.1%). Although an organic carbon source was not added to the medium, a microorganism (Kaistella koreensis) capable of oxidizing organic compounds was found in 7 clones (11.1%). Therefore, the microbial community of spent sulfidic
caustic applied autotrophic denitrification process well corresponds to the substrate components of spent sulfidic caustic.
Through the batch cultivation of microorganisms in UAHGR, the microbial kinetic coefficients of spent sulfidic caustic applied
autotrophic denitrification were estimated to be µ
max
= 0.097 h−1, k
d
= 0.0021 h−1, K
s
= 200 mgNO3
−/L, and Y = 0.31 mgMLVSS/mgNO3
−.
Biotechnology and Bioprocess Engineering 04/2012; 13(1):96-101. · 1.28 Impact Factor
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ABSTRACT: In order to investigate and generalize the effects of carbon and nitrogen sources on the growth of and lipid production in Chlorella sp. 227, several nutritional combinations consisting of different carbon and nitrogen sources and concentrations were given to the media for cultivation of Chlorella sp. 227, respectively. The growth rate and lipid content were affected largely by concentration rather than by sources. The maximum specific growth was negatively affected by low concentrations of carbon and nitrogen. There is a maximum allowable inorganic carbon concentration (less than 500~1,000 mM bicarbonate) in autotrophic culture, but the maximum lipid content per gram dry cell weight (g DCW) was little affected by the concentration of inorganic carbon within the concentration. The lipid content per g DCW was increased when the microalga was cultured with the addition of glucose and bicarbonate (mixotrophic) at a fixed nitrogen concentration and with the lowest nitrogen concentration (0.2 mM), relatively. Considering that lipid contents per g DCW increased in those conditions, it suggests that a high ratio of carbon to nitrogen in culture media promotes lipid accumulation in the cells. Interestingly, a significant increase of the oleic acid amount to total fatty acids was observed in those conditions. These results showed the possibility to induce lipid production of high quality and content per g DCW by modifying the cultivation conditions.
Journal of Microbiology and Biotechnology 10/2011; 21(10):1073-80. · 1.38 Impact Factor
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ABSTRACT: A laboratory-scale Bardenpho process was established to investigate the proper nitrogen loading rate (NLR) when modified spent caustic (MSC) is applied as electron donor and alkalinity source for denitrification. MSC injection induced autotrophic nitrogen removal with sulfur as electron donor and heterotrophic denitrification. The nitrogen removal rate (NRR) did not increase proportionally to NLR. Based on the total nitrogen concentration in the effluent observed in the trials with MSC, the NLR in the influent should not exceed 0.15 kg N/m(3)d in order to satisfy water quality regulations. Microbial communities in the anoxic reactors were characterized by pyrosequencing of 16S rRNA gene sequences amplified by the polymerase chain reaction of DNA extracted from sludge samples. Microbial diversity was lower as MSC dosage was increased, and the injection of MSC caused an increase in SOB belonging to the genus Thiobacillus which is responsible for denitrification using sulfur.
Bioresource technology 08/2011; 102(15):7265-71. · 4.25 Impact Factor
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ABSTRACT: Signal transducer and activator of transcription 3 (STAT3) is an oncogenic transcription factor implicated in carcinogenesis. Here, the role of STAT3 pathway in the antitumor activity of an active ginseng saponin metabolite compound K (CK) was investigated in human multiple myeloma U266 cells. CK increased the cytotoxicity, accumulated the sub-G1 DNA population, cleaved poly (ADP-ribose) polymerase (PARP) and activated caspase-3 in U266 cells. Interestingly, CK inhibited phosphorylation of STAT3 and its upstream activators, the Janus activated kinase 1 (JAK1), but not JAK2. Furthermore, CK enhanced the expression of protein tyrosine phosphatase (PTP) SHP-1, but not PTEN. Additionally, CK down-regulated STAT3 target genes bcl-x(L), bcl-2, survivin, cyclin E and cyclin D1. Conversely, PTP inhibitor pervanadate reversed CK-mediated STAT3 inactivation and cleavages of caspase-3 and PARP. Overall, our findings demonstrate that JAK1/STAT3 signaling mediates CK-induced apoptosis in U266 cells and also suggest the chemopreventive potential of CK for treatment of multiple myeloma.
Food and chemical toxicology: an international journal published for the British Industrial Biological Research Association 03/2011; 49(6):1367-72. · 2.99 Impact Factor
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ABSTRACT: The applicability of modified spent caustic (MSC) as an electron donor for denitrification was evaluated in a lab-scale reactor for the Bardenpho process under various electron donor conditions: (A) no electron donor, (B) methanol, (C) thiosulfate and (D) MSC conditions. TN removal efficiency varied in each condition, 23.1%, 87.8%, 83.7% and 71.7%, respectively. The distribution ratio of nitrifying bacteria and DGGE profile including sulfur-reducing or oxidizing bacteria also varied depending on the conditions. These results indicated that the MSC would be used as an efficient electron donor for denitrification by autotrophic denitrifier in wastewater treatment process.
Bioresource technology 05/2010; 101(9):2988-95. · 4.25 Impact Factor
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ABSTRACT: As spent sulfidic caustic (SSC) from petroleum plants contains a high concentration of alkalinity and sulfur compounds, SSC
can be applied in sewage treatment system as an electron donor for autotrophic denitrification. In our previous study, the
reuse of SSC in the biological nitrogen process was successful, and some neutralization may be required for stable treatment
performance. In this study, the pH of SSC was neutralized to 12.0 from 13.3, and the modified Ludzack-Ettinger process was
conducted for 90 days with the municipal wastewater. Some toxic effects of SSC on microorganisms were tested via a specific
oxygen uptake rate (SOUR) assay. According to the SOUR assay, as compared with no SSC injection condition, SOUR was reduced
by approximately 5.4% when 4 mL SSC/L was injected and the effective concentration of a toxicant causing 50% inhibition of
the microorganism’s activity (EC50) was 22.6 mL/L. During the days of operation, the COD removal and nitrification efficiency were over 53.0 and 98.2%, respectively.
The TN removal efficiency was 56.6% and the nitrogen removal rate (NRR) was 0.15 kg/m3·d when the hydraulic retention time (HRT) in the anoxic tank was 3 h. The ratio of nitrifying bacteria was unaffected by
the HRT, and Nitrobacter spp. and Nitrospira genus existed at similar ratios. The ratio of T. denitrificans increased after the injection of SSC and was approximately 6.5%.
Biotechnology and Bioprocess Engineering 11/2008; 13(6):697-704. · 1.28 Impact Factor
