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1.
Free nitrous acid selectively inhibits and eliminates nitrite oxidizers from nitrifying sequencing batch reactor 总被引:1,自引:0,他引:1
In a complete nitrification sequencing batch reactor (CNSBR), where ammonium containing wastewater (200–1,000 mg N/L) is completely
oxidized to nitrate up to 2.4 kg NH4
+–N/m3 d, both ammonia oxidizers and nitrite oxidizers were enriched in the sludge granules. Quantitative fluorescence in situ hybridization
analyses of the sludge granules of the CNSBR showed that ammonia oxidizers and nitrite oxidizers occupied 31 and 4.2% of total
bacteria, respectively. Most of the nitrite oxidizers were Nitrobacter species (95% of the nitrite oxidizers) and the remainder was Nitrospira species. The population of nitrite oxidizers was significantly higher than that of partial nitrification SBR (PNSBR) where
most of the ammonium was oxidized to nitrite. The PNSBR had 37% (ammonia oxidizers) and 0.4% (nitrite oxidizers) of total
bacteria. Comparative study with CNSBR and PNSBR revealed that free nitrous acid, rather than free ammonia, played a critical
inhibition role to wash out nitrite oxidizers from the reactor. The concentrations of free ammonia and nitrite as well as
free nitrous acid in the CNSBR selected Nitrobacter as the dominant nitrite oxidizers rather than Nitrospira. 相似文献
2.
Kinetic analysis on the two-step processes of AOB and NOB in aerobic nitrifying granules 总被引:1,自引:0,他引:1
Fang Fang Bing-Jie Ni Xiao-Yan Li Guo-Ping Sheng Han-Qing Yu 《Applied microbiology and biotechnology》2009,83(6):1159-1169
Complete granulation of nitrifying sludge was achieved in a sequencing batch reactor. For the granular sludge, batch experiments
were conducted to characterize the kinetic features of ammonia oxidizers (AOB) and nitrite oxidizers (NOB) in the granules
using the respirometric method. A two-step nitrification model was established to determine the kinetic parameters of both
AOB and NOB. In addition to nitrification reactions, the new model also took into account biomass maintenance and mass transfer
through the granules. The yield coefficient, maximum specific growth rate, and affinity constant for ammonium for AOB were
0.21 g chemical oxygen demand (COD) g−1 N, 0.09 h−1, and 9.1 mg N L−1, respectively, whereas the corresponding values for NOB were 0.05 g COD g−1 N, 0.11 h−1, and 4.85 mg N L−1, respectively. The model developed in this study performed well in simulating the oxygen uptake rate and nitrogen conversion
kinetics and in predicting the oxygen consumption of the AOB and NOB in aerobic granules. 相似文献
3.
【目的】为了体现并突出亚硝酸盐还原酶在污水脱氮以及短程硝化中的重要性,对过表达亚硝酸盐还原酶的大肠杆菌进行了污水脱氮的研究。【方法】通过转化带有亚硝酸盐还原酶基因的重组质粒,将亚硝酸盐还原酶在大肠杆菌中过表达,通过分析重组大肠杆菌的产物研究了该酶的表达及还原亚硝酸盐的情况,通过将该重组菌与已报道的硝化-反硝化细菌或生活污水进行混合培养,研究重组菌用于辅助氨氮去除的短程硝化能力。【结果】重组大肠杆菌能正确表达亚硝酸盐还原酶,OD600=2.0的菌悬液在2 h内还原约1 mmol/L的亚硝酸盐,并产生几乎等量的一氧化氮;重组大肠杆菌与Acinetobacter sp.YF14菌株等比例混合时,12 h能够提高氨氮脱氮效率约(36.0±7.4)%,且在4 h时,最大亚硝酸盐的积累量减少37%;重组大肠杆菌(OD600=1.0)12 h内能够提高污水厂活性污泥的脱氮效率约(31.0±5.7)%,且未检测到亚硝酸盐和硝酸盐的积累;溶氧水平对于亚硝酸盐还原酶重组菌辅助脱氮具有明显的影响,中等溶氧量[(6.4?0.7)mg/L]时脱氮效果最好。【结论】过表达亚硝酸盐还原酶的大肠杆菌可以提高污水脱氮的短程硝化能力。 相似文献
4.
Heterotrophic nitrification and aerobic denitrification inAlcaligenes faecalis strain TUD 总被引:1,自引:0,他引:1
E. W. J. van Niel K. J. Braber L. A. Robertson J. G. Kuenen 《Antonie van Leeuwenhoek》1992,62(3):231-237
Heterotrophic nitrification and aerobic and anaerobic denitrification byAlcaligenes faecalis strain TUD were studied in continuous cultures under various environmental conditions. Both nitrification and denitrification activities increased with the dilution rate. At dissolved oxygen concentrations above 46% air saturation, hydroxylamine, nitrite and nitrate accumulated, indicating that both the nitrification and denitrification were less efficient. The overall nitrification activity was, however, essentially unaffected by the oxygen concentration. The nitrification rate increased with increasing ammonia concentration, but was lower in the presence of nitrate or nitrite. When present, hydroxylamine, was nitrified preferentially. Relatively low concentrations of acetate caused substrate inhibition (KI=109 M acetate). Denitrifying or assimilatory nitrate reductases were not detected, and the copper nitrite reductase, rather than cytochrome cd, was present. Thiosulphate (a potential inhibitor of heterotrophic nitrification) was oxidized byA. faecalis strain TUD, with a maximum oxygen uptake rate of 140–170nmol O2·min-1·mg prot-1. Comparison of the behaviour ofA. faecalis TUD with that of other bacteria capable of heterotrophic nitrification and aerobic denitrification established that the response of these organisms to environmental parameters is not uniform. Similarities were found in their responses to dissolved oxygen concentrations, growth rate and ammonia concentration. However, they differed in their responses to externally supplied nitrite and nitrate. 相似文献
5.
Nitrite accumulates during biological denitrification processes when carbon sources are insufficient. Acetate, methanol, and
ethanol were investigated as supplementary carbon sources in the nitrite denitrification process using biogranules. Without
supplementary external electron donors (control), the biogranules degraded 200 mg l−1 nitrite at a rate of 0.27 mg NO2–N g−1 VSS h−1. Notably, 1,500 mg l−1 acetate and 700 mg l−1 methanol or ethanol enhanced denitrification rates for 200 mg l−1 nitrite at 2.07, 1.20, and 1.60 mg NO2–N g−1 VSS h−1, respectively; these rates were significantly higher than that of the control. The sodium dodecyl sulfate polyacrylamide
gel electrophoresis of the nitrite reductase (NiR) enzyme identified three prominent bands with molecular weights of 37–41 kDa.
A linear correlation existed between incremental denitrification rates and incremental activity of the NiR enzyme. The NiR
enzyme activity was enhanced by the supplementary carbon sources, thereby increasing the nitrite denitrification rate. The
capacity of supplementary carbon source on enhancing NiR enzyme activity follows: methanol > acetate > ethanol on molar basis
or acetate > ethanol > methanol on an added weight basis. 相似文献
6.
Use of quantitative real-time PCR to monitor population dynamics of ammonia-oxidizing bacteria in batch process 总被引:2,自引:0,他引:2
A quantitative real-time PCR (QPCR) assay with the TaqMan system was used to quantify 16S rRNA genes of β-proteobacterial
ammonia-oxidizing bacteria (AOB) in a batch nitrification bioreactor. Five different sets of primers, together with a TaqMan
probe, were used to quantify the 16S rRNA genes of β-proteobacterial AOB belonging to the Nitrosomonas europaea, Nitrosococcus mobilis, Nitrosomonas nitrosa, and Nitrosomonas cryotolerans clusters, and the genus Nitrosospira. We also used PCR followed by denaturing gradient gel electrophoresis (DGGE), cloning, and sequencing of their 16S rRNA genes
to identify the AOB species. Seed sludge from an industrial wastewater treatment process controlling high-strength nitrogen
wastewater (500 mg/L NH4
+–N) was used as the inoculum for subsequent batch experiment. The Nitrosomonas nitrosa cluster was the predominant AOB (2.3 × 105 copies/mL) in the start-up period of the batch experiment. However, from the exponential growth period, the Nitrosomonas europaea cluster was the most abundant AOB, and its 16S rRNA gene copy number increased to 8.9 × 106 copies/mL. The competitive dominance between the two AOB clusters is consistent with observed differences in ammonia tolerance
and substrate affinity. Analysis of the DGGE results indicated the presence of Nitrosomonas europaea ATCC19718 and Nitrosomonas nitrosa Nm90, consistent with the QPCR results. 相似文献
7.
Nitrifying granules cultivation in a sequencing batch reactor at a low organics-to-total nitrogen ratio in wastewater 总被引:4,自引:0,他引:4
It is possible to cultivate aerobic granular sludge at a low organic loading rate and organics-to-total nitrogen (COD/N) ratio
in wastewater in the reactor with typical geometry (height/diameter = 2.1, superficial air velocity = 6 mm/s). The noted nitrification
efficiency was very high (99%). At the highest applied ammonia load (0.3 ± 0.002 mg NH4+–N g total suspended solids (TSS)−1 day−1, COD/N = 1), the dominating oxidized form of nitrogen was nitrite. Despite a constant aeration in the reactor, denitrification
occurred in the structure of granules. Applied molecular techniques allowed the changes in the ammonia-oxidizing bacteria
(AOB) community in granular sludge to be tracked. The major factor influencing AOB number and species composition was ammonia
load. At the ammonia load of 0.3 ± 0.002 mg NH4+–N g TSS−1 day−1, a highly diverse AOB community covering bacteria belonging to both the Nitrosospira and Nitrosomonas genera accounted for ca. 40% of the total bacteria in the biomass. 相似文献
8.
Nitrate reduction by Citrobacter diversus under aerobic environment 总被引:17,自引:0,他引:17
A new aerobic denitrifier, Citrobacter diversus, was isolated from both nitrification and denitrification sludge. To monitor the variation in the concentration of nitrogen
oxides, aerobic denitrification by C. diversus was carried out in a batch reactor. When the nitrate concentration was greater than 180 mg N l−1, the nitrate reduction rate became stable. The effect of the C/N ratio on the denitrification activity was also investigated.
The results showed that the optimum denitrification activity was obtained when the C/N ratio was 4–5. The range of the C/N
ratio was higher than that for traditional anoxic denitrification. The effect of the dissolved oxygen concentration was further
studied; and it was found that the range of dissolved oxygen concentrations, both for specific growth rates and for specific
denitrification rates, was 2–6 mg−1. From these results, it can be concluded that both the concentration of dissolved oxygen and the C/N ratio are key factors
in the aerobic denitrification by C. diversus.
Received: 23 November 1999 / Received revision: 4 February 2000 / Accepted: 13 February 2000 相似文献
9.
Denitrification activity of Bradyrhizobium sp. isolated from Argentine soybean cultivated soils 总被引:1,自引:0,他引:1
Leticia Andrea Fernández Elda Beatriz Perotti Marcelo Antonio Sagardoy Marisa Anahí Gómez 《World journal of microbiology & biotechnology》2008,24(11):2577-2585
Two hundred and fifty strains, all of them representatives of native Bradyrhizobium sp., isolated from soils cultivated with soybean have been characterized by their denitrification activity. In addition,
the denitrification potential of those soils was also measured by evaluating the most-probable-number (MPN) of denitrifying
bacteria and the denitrification enzyme assay (DEA). Of the 250 isolates tested, 73 were scored as probable denitrifiers by
a preliminary screening method. Only 41 were considered denitrifiers because they produced gas bubbles in Durham tubes, cultures
reached an absorbance of more than 0.1 and NO3− and NO2− were not present. Ten of these 41 were selected to confirm denitrification and to study denitrification genes. According
to N2O production and cell protein concentration with NO3−, the isolates could be differentiated in three categories of denitrifiers. The presence of the napA, nirK, norC and nosZ genes was detected by production of a diagnostic PCR product using specific primers. RFLP from the 16S-23S rDNA spacer region
(IGS) revealed that denitrifiers strains could be characterized as Bradyrhizobium japonicum and strains which were non-respiratory denitrifiers as B. elkanii. 相似文献
10.
Flores A Nisola GM Cho E Gwon EM Kim H Lee C Park S Chung WJ 《Bioprocess and biosystems engineering》2007,30(3):197-205
The performance of enriched sludge augmented with the B21 strain of Alcaligenes defragrans was compared with that of enriched sludge, as well as with pure Alcaligenes defragrans B21, in the context of a sulfur-oxidizing denitrification (SOD) process. In synthetic wastewater treatment containing 100–1,000 mg
NO3−-N/L, the single strain-seeded system exhibited superior performance, featuring higher efficiency and a shorter startup period,
provided nitrate loading rate was less than 0.2 kg NO3−-N/m3 per day. At nitrate loading rate of more than 0.5 kg NO3−-N/m3 per day, the bioaugmented sludge system showed higher resistance to shock loading than two other systems. However, no advantage
of the bioaugmented system over the enriched sludge system without B21 strain was observed in overall efficiency of denitrification.
Both the bioaugmented sludge and enriched sludge systems obtained stable denitrification performance of more than 80% at nitrate
loading rate of up to 2 kg NO3−-N/m3 per day. 相似文献
11.
Bioenergetic examination of the heterotrophic nitrifier-denitrifier Thiosphaera pantotropha 总被引:1,自引:0,他引:1
Domenic Castignetti 《Antonie van Leeuwenhoek》1990,58(4):283-289
The heterotrophic nitrifying-denitrifying bacterium Thiosphaera pantotropha is remarkable as it nitrifies and denitrifies simultaneously. With respect to nitrogenous compounds, whether nitrification or denitrification results in energy conservation is of interest. Proton translocation studies were performed to determine if energy was conserved by the bacterium during heterotrophic nitrification and denitrification. Hydrazine (N2H
inf5
sup+
) was employed as the heterotrophic nitrification substrate while nitrate, nitrite and nitrous oxide were used as denitrification substrates. Analysis of the data indicate that the bacterium does not conserve energy when hydrazine was the substrate. Conversely, energy was conserved when either nitrate, nitrite or nitrous oxide functioned as the oxidants during denitrification-dependent proton translocation experiments. Thiosphaera pantotropha thus is similar to other heterotrophic nitrifiers-denitrifiers in that it conserves energy while denitrifying but has not been observed to do so when heterotrophically nitrifying. 相似文献
12.
Comparison of biological removal via nitrite with real-time control using aerobic granular sludge and flocculent activated sludge 总被引:2,自引:0,他引:2
The process of nitrification–denitrification via nitrite for nitrogen removal under real-time control mode was tested in two
laboratory-scale sequencing batch reactors (SBRs) with flocculent activated sludge (R1) and aerobic granular sludge (R2) to
compare operational performance and real-time control strategies. The results showed that the average ammonia nitrogen, total
inorganic nitrogen (TIN), and chemical oxygen demand (COD) removal during aeration phase were 97.6%, 57.0%, and 90.1% in R2
compared with 98.6%, 48.7%, and 88.1% in R1. The TIN removed in both SBRs was partially due to the presence of simultaneous
nitrification–denitrification via nitrite, especially in R2. The specific nitrification and denitrification rates in R2 were
0.0416 mgNH4+–N/gSS-min and 0.1889 mgNOX−–N/gSS-min, which were 1.48 times and 1.35 times that of R1. The higher rates for COD removal, nitrification, and denitrification
were achieved in R2 than R1 with similar influent quality. Dissolved oxygen (DO), pH, and oxidization reduction potential,
corresponding to nutrient variations, were used as diagnostic parameters to control the organic carbon degradation and nitrification–denitrification
via nitrite processes in both SBRs. The online control strategy of granular SBR was similar to that of the SBR with flocculent
activated sludge. However, a unique U-type pattern on the DO curve in granular SBR was different from SBR with flocculent
activated sludge in aerobic phase. 相似文献
13.
Simultaneous nutrients and carbon removal during pretreated swine slurry degradation in a tubular biofilm photobioreactor 总被引:1,自引:0,他引:1
Ignacio de Godos Cristina González Eloy Becares Pedro A. García-Encina Raúl Muñoz 《Applied microbiology and biotechnology》2009,82(1):187-194
The biodegradation potential of an innovative enclosed tubular biofilm photobioreactor inoculated with a Chlorella sorokiniana strain and an acclimated activated sludge consortium was evaluated under continuous illumination and increasing pretreated
(centrifuged) swine slurry loading rates. This photobioreactor configuration provided simultaneous and efficient carbon, nitrogen,
and phosphorous treatment in a single-stage process at sustained nitrogen and phosphorous removals efficiencies ranging from
94% to 100% and 70–90%, respectively. Maximum total organic carbon (TOC), NH4
+, and PO4
3− removal rates of 80 ± 5 g C mr
−3 day−1, 89 ± 5 g N mr
−3 day−1, and 13 ± 3 g P mr
−3 day−1, respectively, were recorded at the highest swine slurry loadings (TOC of 1,247 ± 62 mg L−1, N–NH4
+ of 656 ± 37 mg L−1, P–PO4
3+ of 117 ± 19 mg L−1, and 7 days of hydraulic retention time). The unusual substrates diffusional pathways established within the phototrophic
biofilm (photosynthetic O2 and TOC/NH4
+ diffusing from opposite sides of the biofilm) allowed both the occurrence of a simultaneous denitrification/nitrification
process at the highest swine slurry loading rate and the protection of microalgae from any potential inhibitory effect mediated
by the combination of high pH and high NH3 concentrations. In addition, this biofilm-based photobioreactor supported efficient biomass retention (>92% of the biomass
generated during the pretreated swine slurry biodegradation). 相似文献
14.
Simultaneous nitrification and denitrification by diverse <Emphasis Type="Italic">Diaphorobacter</Emphasis> sp. 总被引:2,自引:0,他引:2
Eight bacterial isolates closely related to Diaphorobacter sp. were isolated from activated biomass surviving on wastewater laden with dyes and nitro-substituted chemicals and were
identified by 16S rDNA sequence analysis. The isolates showed sequence similarity of 99–100% to other Diaphorobacter strains such as ZY 2006b, F2, NA5, PCA039, D. nitroreducens KSP4, and KSP3 and 98–99% sequence homology to D. nitroreducens NA10B (type strain JCM 11421). Neighbor-joining tree revealed that all the eight strains formed tight cluster together and
also showed close clustering with other Diaphorobacter strains. Isolates demonstrated the ability to perform simultaneous nitrification and denitrification under aerobic conditions.
Strains HPC 805, 815, 821, and 856 gave highest chemical oxygen demand removal (85–93%) and ammonia removal (92–96%), which
correlated well with higher growth rates of the cultures. Simultaneously, complete removal of nitrate supplied in the medium
in presence of ammonium and acetate (electron donor) was observed in addition to aerobic nitrite release from ammonium. Thus,
the above strains showed ability to perform partial nitrification followed by further aerobic removal of common intermediate
nitrite, which indicated their potential application in treatment systems for treatment of high-nitrogen-containing wastewaters. 相似文献
15.
Based on the comparative 16S rRNA gene sequence analysis of fecal DNAs, we identified one human-, three cow-, and two pig-specific
Bacteroides–Prevotella 16S rRNA genetic markers, designed host-specific real-time polymerase chain reaction (real-time PCR) primer sets, and successfully
developed real-time PCR assay to quantify the fecal contamination derived from human, cow, and pig in natural river samples.
The specificity of each newly designed host-specific primer pair was evaluated on fecal DNAs extracted from these host feces.
All three cow-specific and two pig-specific primer sets amplified only target fecal DNAs (in the orders of 9–11 log10 copies per gram of wet feces), showing high host specificity. This real-time PCR assay was then applied to the river water
samples with different fecal contamination sources and levels. It was confirmed that this assay could sufficiently discriminate
and quantify human, cow, and pig fecal contamination. There was a moderate level of correlation between the Bacteroides–Prevotella group-specific 16S rRNA gene markers with fecal coliforms (r
2 = 0.49), whereas no significant correlation was found between the human-specific Bacteroides 16S rRNA gene with total and fecal coliforms. Using a simple filtration method, the minimum detection limits of this assay
were in the range of 50–800 copies/100 ml. With a combined sample processing and analysis time of less than 8 h, this real-time
PCR assay is useful for monitoring or identifying spatial and temporal distributions of host-specific fecal contaminations
in natural water environments. 相似文献
16.
ImGyu Byun JeungJin Park SoRa Park TaeHo Lee TaeJoo Park 《Biotechnology and Bioprocess Engineering》2008,13(1):96-101
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
−. 相似文献
17.
Nucleotide variation at several cold candidate genes including seven members of the dehydrin gene family was surveyed in haplotypes
of Scots pine (Pinus sylvestris) sampled in populations showing divergence for cold tolerance in Europe. Patterns of nucleotide diversity, linkage disequilibrium,
and frequency spectrum of alleles were compared between north and south populations to search for signs of directional selection
potentially underlying adaptation to cold. Significant differentiation between populations in allelic frequency or haplotype
structure was detected at dhn1, dhn3, and abaH loci. Allelic dimorphism with no evidence of haplotype clustering by geographical distribution was found at dhn9. An excess of fixed non-synonymous mutations as compared to the outgroup P. pinaster pine species was found at dhn1. Differences in nucleotide polymorphisms were found between the members of the Kn class of dehydrin upregulated during cold
acclimation (average πsil = 0.004) as compared to the SKn class (average πsil = 0.024). The multilocus nucleotide diversity at silent sites (θ
W = 0.009) was moderate compared to other conifer species, but higher than previous estimates for Scots pine. There was an
excess of rare and high frequency derived variants as revealed by significantly negative multilocus value of Tajima’s D (D = −0.72, P < 0.01) and negative mean value of Fay and Wu H statistics (H = −0.50). The level of linkage disequilibrium decayed rapidly with an average expected r
2 of 0.2 at about 200 bp. Overall, there was a positive correlation between polymorphism and divergence at ten loci when outgroup
sequence was available. The discovered polymorphism will be used for further evaluation of the adaptive role of genes through
association mapping studies.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
18.
Malaysia is the world’s leading producer of palm oil products that contribute US$ 7.5 billion in export revenues. Like any
other agro-based industries, it generates waste that could be utilized as a source of organic nutrients for microalgae culture.
Present investigation delves upon Isochrysis sp. culture in POME modified medium and its utilization as a supplement to Nanochloropsis sp. in rotifer cultures. The culture conditions were optimized using a 1 L photobioreactor (Temp: 23°C, illumination: 180 ∼ 200 μmol
photons m−2s−1, n = 6) and scaled up to 10 L outdoor system (Temp: 26–29°C, illumination: 50 ∼ 180 μmol photons m−2s−1, n = 3). Algal growth rate in photobioreactor (μ = 0.0363 h−1) was 55% higher compared to outdoor culture (μ = 0.0163 h−1), but biomass production was 1.3 times higher in outdoor culture (Outdoor = 91.7 mg m−2d−1; Photobioreactor = 69 mg m−2d−1). Outdoor culture produced 18% higher lipid; while total fatty acids (FA) was not significantly affected by the change in
culture systems as both cultures yield almost similar concentrations of fatty acids per gram of sample (photobioreactor = 119.17 mg
g−1; outdoor culture = 104.50 mg g−1); however, outdoor cultured Isochrysis sp. had 26% more polyunsaturated fatty acids (PUFAs). Rotifers cultured in Isochrysis sp./ Nanochloropsis sp. (1:1, v/v) mixture gave similar growth rate as 100% Nanochoropsis sp. culture (μ = 0.40 d−1), but had 45% higher counts of rotifers with eggs (t = 7, maximum). The Isochrysis sp. culture successfully lowered the nitrate (46%) and orthophosphate (83%) during outdoor culture. 相似文献
19.
Characterization of the superoxide dismutase SOD1 gene of Kluyveromyces marxianus L3 and improved production of SOD activity 总被引:1,自引:0,他引:1
Raimondi S Uccelletti D Matteuzzi D Pagnoni UM Rossi M Palleschi C 《Applied microbiology and biotechnology》2008,77(6):1269-1277
Superoxide dismutase (SOD) activity is one major defense line against oxidative stress for all of the aerobic organisms, and
industrial production of this enzyme is highly demanded. The Cu/Zn superoxide dismutase gene (KmSOD1) of Kluyveromyces marxianus L3 was cloned and characterized. The deduced KmSod1p protein shares 86% and 71% of identity with Kluyveromyces lactis and Saccharomyces cerevisiae Sod1p, respectively. The characteristic motifs and the amino acid residues involved in coordinating copper and zinc and in
enzymatic function were conserved. To the aim of developing a microbial production of Cu/Zn superoxide dismutase, we engineered
the K. marxianus L3 strain with the multicopy plasmid YG-KmSOD1 harboring the KmSOD1 gene. The production of KmSOD1p in K. marxianus L3 and K. marxianus L3 (pYG-KmSOD1) in response to different compositions of the culture medium was evaluated. The highest specific activity
(472 USOD mgprot
−1) and the highest volumetric yield (8.8 × 105 USOD l−1) were obtained by the recombinant strain overexpressing KmSOD1 in the presence of Cu2+ and Zn2+ supplements to the culture media. The best performing culture conditions were positively applied to a laboratory scale fed-batch
process reaching a volumetric yield of 1.4 × 106 USOD l−1.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
20.
In this study, sludge was taken from a municipal wastewater treatment plant that contained a nearly equal number of archaeal
amoA genes (5.70 × 106 ± 3.30 × 105 copies mg sludge−1) to bacterial amoA genes (8.60 × 106 ± 7.64 × 105 copies mg sludge−1) and enriched in three continuous-flow reactors receiving an inorganic medium containing different ammonium concentrations:
2, 10, and 30 mM NH4+–N (28, 140, and 420 mg N l−1). The abundance and communities of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in enriched nitrifying
activated sludge (NAS) were monitored at days 60 and 360 of the operation. Early on, between day 0 and day 60 of reactor operation,
comparative abundance of AOA amoA genes to AOB amoA genes varied among the reactors depending on the ammonium levels found in the reactors. As compared to the seed sludge, the
number of AOA amoA genes was unchanged in the reactor with lower ammonium level (0.06 ± 0.04 mgN l−1), while in the reactors with higher ammonium levels (0.51 ± 0.33 and 0.25 ± 0.10 mgN l−1), the numbers of AOA amoA genes were deteriorated. By day 360, AOA disappeared from the ammonia-oxidizing consortiums in all reactors. The majority
of the AOA sequences from all NASs at each sampling period fell into a single AOA cluster, however, suggesting that the ammonium
did not affect the AOA communities under this operational condition. This result is contradictory to the case of AOB, where
the communities varied significantly among the NASs. AOB with a high affinity for ammonia were present in the reactors with
lower ammonium levels, whereas AOB with a low affinity to ammonia existed in the reactors with higher ammonium levels. 相似文献