The effect of decreasing alkalinity on microbial community dynamics in a sulfate-reducing bioreactor as analyzed by PCR-SSCP

Alkalinity refers to the substance that can react with acid in an aqueous system, which measures its capac-ity to neutralize hydrogen iron (H ). Alkalinity influ-ences greatly the stability and treatment ability of an-aerobic bioreactor. It has been well …     

Monitoring of microbial community structure and succession in the biohydrogen production reactor by denaturing gradient gel electrophoresis (DGGE)

To study the structure of microbial communities in the biological hydrogen production reactor and determine the ecological function of hydrogen producing bacteria, anaerobic sludge was obtained from the continuous stirred tank reactor (CSTR) in different periods of time, and the diversity and dynamics of microbial communities were investigated by denaturing gradient gel electrophoresis (DGGE). The results of DGGE demonstrated that an obvious shift of microbial population happened from the beginning of star-up to the 28th day, and the ethanol type fermentation was established. After 28 days the structure of microbial community became stable, and the climax community was formed. Comparative analysis of 16S rDNA sequences from reamplifying and sequencing the prominent bands indicated that the dominant population belonged to low G+C Gram-positive bacteria (Clostridium sp. andEthanologenbacterium sp.), β-proteobacteria (Acidovorax sp.), γ-proteobacteria (Kluyvera sp.), Bacteroides (uncultured bacterium SJA-168), and Spirochaetes (uncultured eubacterium E1-K13), respectively. The hydrogen production rate increased obviously with the increase ofEthanologenbacterium sp.,Clostridium sp. and uncultured Spirochaetes after 21 days, meanwhile the succession of ethanol type fermentation was formed. Throughout the succession the microbial diversity increased however it decreased after 21 days. Some types ofClostridium sp.Acidovorax sp.,Kluyvera sp., and Bacteroides were dominant populations during all periods of time. These special populations were essential for the construction of climax community. Hydrogen production efficiency was dependent on both hydrogen producing bacteria and other populations. It implied that the cometabolism of microbial community played a great role of biohydrogen production in the reactors.     

Monitoring of microbial community structure and succession in the biohydrogen production reactor by denaturing gradient gel electrophoresis (DGGE)

Biohydrogen production has been concerned ex-tremely as a new technology of energy resource pro-duction by many scientists[1—4]. Enhancement of hy-drogen production efficiency and cutting down the operating cost are very important problems, which are the limiting factors for the industrialization of hydro-gen production process. The fermentation hydrogen production technology offers a new method to resolve these difficulties[5—8]. Compared with photosynthetic hydrogen production possesses, f…     

Microbial community analysis of simultaneous ammonium removal and Fe3+ reduction at different influent ammonium concentrations

This study investigates the impacts of influent ammonium concentrations on the microbial community in immobilized heterotrophic ammonium removal system. Klebsiella sp. FC61, the immobilized species, has the ability to perform simultaneous ammonium removal and Fe³⁺ reduction. It was found that average ammonium removal rate decreased from 0.308 to 0.157 mg/L/h, as the influent NH₄ ⁺-N was reduced from 20 to 10 mg/L. Meanwhile, at a total Fe³⁺ concentration of 20 mg/L, the average Fe³⁺ reduction removal efficiency and rate decreased from 44.61% and 0.18 mg/L/h, to 27.10% and 0.11 mg/L/h, respectively. High-throughput sequencing was used to observe microbial communities in bioreactor Samples B1, B2, and B3, after exposure to different influent NH₄ ⁺-N conditions. Results show that higher influent NH₄ ⁺-N concentrations increased microbial richness and diversity and that Klebsiella sp. FC61 play a functional role in the simultaneous removal of NH₄ ⁺-N and Fe³⁺ reduction in bioreactor systems.

     

Enhancement of 2,4-dinitrotoluene biodegradation by Burkholderia sp. in sand bioreactors using bacterial hemoglobin technology

Continuous flow sand column bioreactor experiments were conducted to investigate the effect of 2,4-dinitrotoluene (DNT) concentration (i.e. DNT loading rate) and influent dissolved oxygen (DO) concentration on aerobic biodegradation of DNT by wild type (DNT) and recombinant (YV1) Burkholderia sp., the latter containing plasmid pSC160 which carries the gene (vgb) encoding the hemoglobin (VHb) from the bacterium Vitreoscilla. The experiments were conducted in two continuous flow packed bed sand column bioreactors, one growing the wild type strain and the other growing YV1. Under oxygen-rich feed conditions (6.8 mg DO/L in the feed) with an influent DNT concentration of 99.6 mg/L (DNT loading rate approximately = 9.2 mg/m2/day), the effluent DNT concentration from the wild type bioreactor reached 0.7 mg DNT/L in 40 days whereas it was less than 0.2 mg DNT/L for the YV1 bioreactor in about 25 days. When influent DNT concentration was increased to 214 mg/L (DNT loading rate approximately = 20.3 mg/m2/day) while maintaining the same influent DO level of 6.8 mg/L, the effluent DNT concentration increased to about 5 mg/L for the wild type bioreactor whereas it was maintained at less than 0.2 mg/L for the YV1 bioreactor. Additionally, when influent DO was reduced from 6.8 mg/L to 3.1 mg/L while the influent DNT concentration remained at 214 mg/L, the effluent DNT concentration increased to more than 20 mg/L for the wild type bioreactor but up to only 1.7 mg/L for the YV1 bioreactor. A subsequent increase of influent DO back to 6.6 mg/L reduced the effluent DNT concentration to about 5 mg/L for the wild type bioreactor and to 0.10-0.19 mg/L for the YV1 bioreactor. These results confirm the utility of vgb technology to enhance biodegradation of aromatic compounds under hypoxic conditions and also that this enhancement can be maintained over extended periods of time as evidenced by plasmid stability in Burkholderia YV1.     

Performance and bacterial community shifts during bioremediation of acid mine drainage from two Portuguese mines

The performance of two up-flow anaerobic packed bed systems (UAPB) to treat acid mine drainage (AMD) from the Portuguese mines São Domingos and Tinoca was investigated. The response of bacterial populations to influent characteristics was also analysed by temperature gradient gel electrophoresis (TGGE). Effective neutralisation (pH raised from 2.8 to 6.5) and removal of metals (>99%) and sulphate (>72%) were observed independently of the AMD source. TGGE fingerprinting and phylogenetic analysis of 16S rRNA gene revealed that the structure of the bacterial consortia developed in each bioreactor was different. The main bacterial groups involved in the treatment of AMD from Tinoca mine were Desulfovibrio sp., Clostridium sp., Desulfitobacterium sp. and members of Bacteroidales order. These bacterial groups were also present in the community developed in the UAPB fed with AMD from São Domingos mine but an unidentified bacterium and bacteria affiliated to Citrobacter and Cronobacter genera were detected only in this last system. The results of present study showed that the AMD source fed to the system was determinant for the establishment of different bacterial populations. Furthermore, the potential of the bioremediation systems for the production of water for irrigation purposes was demonstrated.     

Dynamics of bacterial community in up-flow anaerobic packed bed system for acid mine drainage treatment using wine wastes as carbon source

The dynamics of the bacterial populations in an up-flow anaerobic packed bed system (UAPB), applied in acid mine drainage treatment using wine wastes as carbon and nutrients source was elucidated by temperature gradient gel electrophoresis (TGGE) analysis. Moreover, TGGE fingerprints of the bacterial communities developed in a UAPB fed with wine wastes and a UAPB fed with pure ethanol were compared. TGGE fingerprinting and phylogenetic analysis showed that the composition of the community in the UAPB fed with wine wastes remained stable during whole time of operation and its bacterial diversity was higher. The bacterial community of the UAPB fed with wine wastes was composed by bacteria affiliated with Desulfovibrio, Clostridium, Citrobacter and Cronobacter genera and with Bacteroidales order, sp. The dominant community developed in the UAPB fed with ethanol was composed by bacteria affiliated with Desulfovibrio sp. The presence of several bacterial groups in the bioreactor fed with wine wastes suggests a synergistic interaction between the different populations. Syntrophic interaction may be the key factor for the utilization of wine wastes, a complex organic substrate, as carbon and electron source for sulphate reduction.     

Optimized operational parameters of a pilot scale membrane bioreactor for high-strength organic wastewater treatment

A pilot-scale test was conducted in a submerged membrane bioreactor (SMBR) for 452 days to treat high-strength traditional Chinese medicine wastewater from two-phase anaerobic digest effluent. This study focuses on the effects of operational parameters on effluent quality of a SMBR. The parameters include shorter hydraulic retention time (HRT), higher influent COD concentration, higher COD loading rate and mixed liquor suspended solids (MLSS). The experimental results demonstrated that when HRT was 5 h and the influent COD was less than 3000 mg L⁻¹, the effluent quality of the SMBR evaluated from its COD content (COD_filt) could meet the accepted Chinese standards for water reclamation; when HRT was 3.2 h and the influent COD was less than 3000 mg L ⁻¹, or HRT was 5 h and the influent COD fluctuated between 3000 and 6000 mg L⁻¹, the effluent quality of the SMBR could meet the normal Chinese discharged standard. Statistical analyses showed that COD_filt correlated positively with the COD loading rate. It correlated negatively with the MLSS for MLSS values between 7543 and 13 694 mg L⁻¹. When MLSS was >13 694 mg L⁻¹ it correlated positively with COD_filt. Based on experimental values from SMBR and on values predicted by a simulation model generated using the back propagation neural network (BPNN) theory, the optimum operational parameters for the treatment of a high-strength TCM wastewater were as follows: HRT was 5 h, SRT was 100 day, COD loading rate was<20.5 kg m⁻³ d⁻¹, the range of MLSS was 7543–13 694 mg L⁻¹.     

Quantitative analysis of a high-rate hydrogen-producing microbial community in anaerobic agitated granular sludge bed bioreactors using glucose as substrate

Fermentative H₂ production microbial structure in an agitated granular sludge bed bioreactor was analyzed using fluorescence in situ hybridization (FISH) and polymerase chain reaction-denatured gradient gel electrophoresis (PCR-DGGE). This hydrogen-producing system was operated at four different hydraulic retention times (HRTs) of 4, 2, 1, and 0.5 h and with an influent glucose concentration of 20 g chemical oxygen demand/l. According to the PCR-DGGE analysis, bacterial community structures were mainly composed of Clostridium sp. (possibly Clostridium pasteurianum), Klebsiella oxytoca, and Streptococcus sp. Significant increase of Clostridium/total cell ratio (68%) was observed when the reactor was operated under higher influent flow rate. The existence of Streptococcus sp. in the reactor became more important when operated under a short HRT as indicated by the ratio of Streptococcus probe-positive cells to Clostridium probe-positive cells changing from 21% (HRT 4 h) to 38% (HRT 0.5 h). FISH images suggested that Streptococcus cells probably acted as seeds for self-flocculated granule formation. Furthermore, combining the inspections with hydrogen production under different HRTs and their corresponding FISH analysis indicated that K. oxytoca did not directly contribute to H₂ production but possibly played a role in consuming O₂ to create an anaerobic environment for the hydrogen-producing Clostridium.     

Biotreatment of Simulated Textile Dye Effluent Containing malachite green by an Up-Flow Immobilized Cell Bioreactor

An up-flow immobilized cell bioreactor was developed using a microbial consortium, consisting of Bacillus sp., Alcaligenes sp. and Aeromonas sp., immobilized on refractory brick pieces as immobilization support. malachite green, a model triphenylmethane dye was decolourized by more than 93% within 48 h (operating conditions: initial dye concentration 30 mg l⁻¹; flow rate 6 ml h⁻¹). The analytical studies based on TLC and ¹H NMR showed degradation of the aromatic rings of the malachite green into simpler metabolic intermediates.     

Nitrifying bacterial community structures and their nitrification performance under sufficient and limited inorganic carbon conditions

This study examined the hypothesis that different inorganic carbon (IC) conditions enrich different ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) populations by operating two laboratory-scale continuous-flow bioreactors fed with 15 and 100 mg IC/L, respectively. During this study, both bioreactors maintained satisfactory nitrification performance and stably oxidized 250 mg?N/L of influent ammonium without nitrite accumulation. Based on results of cloning/sequencing and terminal restriction fragment length polymorphism targeting on the ammonia monooxygenase subunit A (amoA) gene, Nitrosomonas nitrosa lineage was identified as the dominant AOB population in the high-IC bioreactor, while Nitrosomonas europaea and Nitrosomonas nitrosa lineage AOB were dominant in the low-IC bioreactor. Results of real-time polymerase chain reactions for Nitrobacter and Nitrospira 16S rRNA genes indicated that Nitrospira was the predominant NOB population in the high-IC bioreactor, while Nitrobacter was the dominant NOB in the low-IC bioreactor. Furthermore, batch experiment results suggest that N. europaea and Nitrobacter populations are proliferated in the low-IC bioreactor due to their higher rates under low IC conditions despite the fact that these two populations have been identified as weak competitors, compared with N. nitrosa and Nitrospira, under low ammonium/nitrite environments. This study revealed that in addition to ammonium/nitrite concentrations, limited IC conditions may also be important in selecting dominant AOB/NOB communities of nitrifying bioreactors.     

Biodegradation of acid blue-15, a textile dye,by an up-flow immobilized cell bioreactor

Acid blue-15, a complex and resonance-stabilized triphenylmethane (TPM) textile dye, resistant to transformation, was decolorized/degraded in an up-flow immobilized cell bioreactor. A consortium comprised of isolates belonging to Bacillus sp., Alcaligenes sp. and Aeromonas sp. formed a multispecies biofilm on refractory brick pieces used as support material. The TPM dye was degraded to simple metabolic intermediates in the bioreactor with 94% decolorization at a flow rate of 4 ml h^–1.     

Antibiotic activity of tigecycline against clinical pathogens by the micro dilution method

Resistant pathogens are the cause of clinical infections which threatening the patients lives and challenging the health systems through their economic importance. Therefore, new antibacterial agents with a broader spectrum of activity that protect against development of resistance are required. Tigecycline (Tygacil, Wyeth) is a relatively new FDA and EMEA approved glycylcycline antimicrobial with an expanded broad-spectrum activity against pathogens involved in complicated skin and skin structure infections. In this study we evaluated the in vitro activity of tigecycline in comparison to 14 other antibiotics against 182 clinical pathogens by use of the micro dilution method. In overall, tigecycline exhibited the lowest Minimum Inhibitory Concentration (MIC) values in almost all bacteria with a mean of 0.52 ± 1.25 mg/L, followed by meropenem and levofloxacin (mean MIC values 1.29 ± 2.52 and 1.45 ± 3.078 mg/L, respectively). MIC50 and MIC90 values of tigecycline were: 0.06 and 0.15 mg/L for E. coli, 0.12 and 1.00 mg/L for Klebsiella sp., 0.12 and 0.85 mg/L for various Enterobacter sp., 1.00 and 8.00 mg/L for Pseudomonas sp., 0.25 and 1.00 mg/L for Acinetobacter sp., 0.06 and 0.12 mg/L for Serratia sp., 0.12 and 0.25 mg/L for Staphylococcus aureus, 0.5 and 5.00 mg/L for Streptococcus sp. The MIC values recorded were among the lowest in recent literature for Acinetobacter sp. (included A. baumannii), and comparable to those obtained for Klebsiella, Serratia and Enterobacter indicating that tigecycline has a promising in vitro activity.     

Mixing characteristics and liquid circulation in a new multi-environment bioreactor

The theoretical and experimental aspects of the hydrodynamics and mixing in a new multi-environment bioreactor that uses the air-lift design were investigated. This study focused on the mixing characteristics, residence time distribution, liquid circulation between three zones of aerobic, microaerophilic and anoxic, and liquid displacement in the bioreactor at influent flow rates of 720–1,450 L/day and air flow rates of 15–45 L/min. The theoretical analysis of liquid displacement led to the estimation of the specific rate of liquid discharge from the bioreactor at any given influent flow rate, and the number of liquid circulations between various bioreactor zones before the discharge of a given quantity of wastewater. The ratio of mean residence time to the overall hydraulic retention time (t _m/HRT) decreased with the increase of air flow rate at any given influent flow rate, and approached unity at higher air flow rates. Mixing was characterized in terms of the axial dispersion coefficient and Bodenstein number, demonstrating a linear relationship with the superficial gas velocity. A correlation was developed between the Bodenstein number and the Froude number. The study of liquid circulation between the zones showed that less than 1.5 % of the circulating liquid escapes circulation at each cycle and flows towards the outer clarifier, while the percentage of escaped liquid decreases with increasing air flow rate at a given influent flow rate. The specific rate of liquid discharge from the bioreactor increased from 0.19 to 0.69 h^?1 with the increase of air and influent flow rates from 15 to 45 L/min and 500 to 1,450 L/day, respectively. Under the examined operating conditions, mixed liquor circulates between 364 and 1,698 times between the aerobic, microaerophilic and anoxic zones before 99 % of its original volume is replaced by the influent wastewater.     

Morphological and genetic characteristics of sea bass,Lateolabrax japonicus, from the Ariake Sea, Japan

Sea bass,Lateolabrax japonicus, from the Ariake Sea, characterized by black dots on the lateral body region as in the Chinese sea bass,L. sp., were examined and compared morphologically and genetically withL. japonicus andL. sp. Some meristic characters of the Ariake form tended to fall midway between values for the two former species. Genetic features, evaluated by isozyme analyses, indicated that the Ariake form as represented a simple Mendelian population, there being no significant differences from a Hardy-Weinberg equilibrium according to chi-square tests. Although some extreme differences in allelic frequencies were found at some loci betweenL. japonicus andL. sp., the Ariake form possessed many heterozygotes at thePROT-1 ^* locus, in addition to allelic frequencies at some loci conforming to those ofL. sp. Average allele numbers per locus, rate of polymorphic loci and average heterozygosity of the Ariake form were higher than for eitherL. japonicus orL. sp., indicating high genetic variation in the former. The results suggested that the Ariake population is genetically independent of other populations ofL. japonicus, but might be genetically influenced byL. sp.     

Nitrifying bacterial growth inhibition in the presence of algae and cyanobacteria

Nitrifying bacteria, cyanobacteria, and algae are important microorganisms in open pond wastewater treatment systems. Nitrification involving the sequential oxidation of ammonia to nitrite and nitrate, mainly due to autotrophic nitrifying bacteria, is essential to biological nitrogen removal in wastewater and global nitrogen cycling. A continuous flow autotrophic bioreactor was initially designed for nitrifying bacterial growth only. In the presence of cyanobacteria and algae, we monitored both the microbial activity by measuring specific oxygen production rate (SOPR) for microalgae and cyanobacteria and specific oxygen uptake rate (SOUR) for nitrifying bacteria. The growth of cyanobacteria and algae inhibited the maximum nitrification rate by a factor of 4 although the ammonium nitrogen fed to the reactor was almost completely removed. Terminal restriction fragment length polymorphism (T‐RFLP) analysis indicated that the community structures of nitrifying bacteria remained unchanged, containing the dominant Nitrosospira, Nitrospira, and Nitrobacter species. PCR amplification coupled with cloning and sequencing analysis resulted in identifying Chlorella emersonii and an uncultured cyanobacterium as the dominant species in the autotrophic bioreactor. Notwithstanding their fast growth rate and their toxicity to nitrifiers, microalgae and cyanobacteria were more easily lost in effluent than nitrifying bacteria because of their poor settling characteristics. The microorganisms were able to grow together in the bioreactor with constant individual biomass fractions because of the uncoupled solids retention times for algae/cyanobacteria and nitrifiers. The results indicate that compared to conventional wastewater treatment systems, longer solids retention times (e.g., by a factor of 4) should be considered in phototrophic bioreactors for complete nitrification and nitrogen removal. Biotechnol. Bioeng. 2010;107: 1004–1011. © 2010 Wiley Periodicals, Inc.     

Characterization of sulfur oxidation by an autotrophic sulfur oxidizer,Thiobacillus sp. ASWW-2

An autotrophic sulfur oxidizer,Thiobacillus sp. ASWW-2, was isolated from activated sludge, and its sulfur oxidation activity was characterized.Thiobacillus sp. ASWW-2 could oxidize elemental sulfur on the broad range from pH 2 to 8. When 5–50 g/L of elemental sulfur was supplemented as a substrate, the growth and sulfur oxidation activity ofThiobacillus sp. ASWW-2 was not inhibited. The specific sulfur oxidation rate of strain ASWW-2 decreased gradually until sulfate was accumulated in medium up to 10 g/L. In the range of sulfate concentration from 10 g/L to 50 g/L, the sulfur oxidation rate could keep over 2.0 g-S/g-DCW-d. It indicated thatThiobacillus sp. ASWW-2 has tolerance to high concentration of sulfate.     

Metazoan parasite communities of wild Leporinus friderici (Characiformes: Anostomidae) from Amazon River system in Brazil

This study compared the structure of metazoan parasite communities in two populations of Leporinus friderici from two rivers of the Amazon River system in Brazil. Jainus leporini, Urocleidoides paradoxus, Urocleidoides sp., Tereancistrum parvus, Tereancistrum sp., Clinostomum marginatum, Procamallanus (Spirocamallanus) inopinatus, Contracaecum sp., Octospiniferoides incognita and Ergasilus sp. were found in both hosts. There were differences in species richness of parasites, Shannon index and the evenness between both host populations, because the parasite community showed a similarity of only 33%. Parasites of both host populations had an aggregated dispersion. Host size also contributes to the differences between the populations of hosts investigated, and the feeding habit contributes to the occurrence of endoparasites in L. friderici, an intermediate host for these parasites. The existence of variation in infracommunity and community of parasites for the same host species from different localities indicates the presence of an uneven distribution in terms of species and density of parasites, which are intermediate hosts, and some of them constitute food items for L. friderici in the localities surveyed.     

Production of recombinant HIV‐1 nef protein using different expression host systems: A techno‐economical comparison

Three popular expression host systems Escherichia coli, Pichia pastoris and Drosophila S2 were analyzed techno‐economically using HIV‐1 Nef protein as the model product. On scale of 100 mg protein, the labor costs corresponded to 52–83% of the manufacturing costs. When analyzing the cost impact of the different phases (strain/cell line construction, bioreactor production, and primary purification), we found that with the microbial host systems the strain construction phase was most significant generating 56% (E. coli) and 72% (P. pastoris) of the manufacturing costs, whereas with the Drosophila S2 system the cell line construction and bioreactor production phases were equally significant (46 and 47% of the total costs, respectively). With different titers and production goal of 100 mg of Nef protein, the costs of P. pastoris and Drosophila S2 systems were about two and four times higher than the respective costs of the E. coli system. When equal titers and bioreactor working volumes (10 L) were assumed for all three systems, the manufacturing costs of the bioreactor production of the P. pastoris and Drosophila S2 systems were about two and 2.5 times higher than the respective costs of the E. coli system. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Characterization of a microbial community capable of reducing perchlorate and nitrate in high salinity

Denitrifying up-flow packed-bed bioreactors fed with perchlorate and nitrate allowed for the examination of the impact of a variety of salt conditions (up to 10% w/v NaCl) on the complete perchlorate and nitrate removal capacity of the reactor using activated sludge taken from a municipal wastewater treatment plant. Based on the evaluation of the microbial community in the bioreactor by cloning analysis, Clostridium sp. and a Rhodocyclaceae bacteria were identified as the dominant clones. This suggests that they may be tolerant to high salt and can reduce both nitrate and perchlorate in such conditions.