RESUMO
Bacterial communities and metabolites in kimchi fermented under conventional conditions (CC) compared to CO2-rich environments (CO2) were analyzed. After a 20-day fermentation, lactic and acetic acid productions were 54 and 69 mM under CC, and 19 and 12 mM under CO2, respectively. The final pH of kimchi fermented under CC (CC-fermenting) and CO2 (CO2-fermenting) were 4.1 and 4.7, respectively. For bacterial communities, OTU and Chao1 indices were both 35 in fresh kimchi, 10 and 15 in CC-fermenting kimchi, and 8 and 24 in CO2-fermenting kimchi, respectively. Shannon and Simpson indices were 3.47 and 0.93 in fresh kimchi, 1.87-0.06 and 0.46-0.01 in CC-fermenting kimchi, and 1.65-0.44 and 0.63-0.12 in CO2-fermenting kimchi, respectively. Non-lactic acid bacteria were eliminated in fermenting kimchi after 12 days under CC and 6 days under CO2. I conclude that carbon dioxide can alter bacterial communities, reduce metabolite production, and improve fermented kimchi quality.
Assuntos
Brassica/metabolismo , Dióxido de Carbono/química , Fermentação , Alimentos Fermentados , Lactobacillales/metabolismo , Brassica/microbiologia , Concentração de Íons de Hidrogênio , Lactobacillales/classificação , Lactobacillales/genética , Filogenia , Especificidade da EspécieRESUMO
Soy sauce prepared via direct fermentation of defatted soybean meal (DFSM) using halophiles without addition of dried, fermented soybeans or meju was evaluated. DFSM was fermented using single and mixed cultures of Oceanobacillus kimchii and Bacillus pumilus under 18% salinity conditions. Amounts of total organic nitrogen, free amino acids, and organic acids in soy sauce prepared with the mixed culture were slightly higher than sauces prepared with single culture. The ingredient content was higher in soy sauce prepared via direct fermentation of DFSM than soy sauce prepared with meju. Microorganisms detected in DFSM fermentation were not detected in the meju culture, except for the 2 halophiles, based on metagenomic analysis. Direct fermentation of DFSM is better than using meju for preparation of soy sauce.
RESUMO
The diversity of thermophilic bacteria was not significantly altered while growing in a defatted soybean meal (DFSM) slurry at 60 °C for 10, 20, and 30 days. Five species of thermophilic bacteria, which belong to the genera Aeribacillus (temperature gradient gel electrophoresis [TGGE] band no. 1), Saccharococcus (TGGE band no. 2), Geobacillus (TGGE band no. 3), Bacillus (TGGE band no. 4), and Anoxybacillus (TGGE band no. 5), were detected in the fermenting DFSM slurry. The cell-free culture fluid obtained from the fermenting DFSM slurry on day 14 hydrolyzed starch and soy protein at 60 °C but not at 30 °C. Soy sauce (test soy sauce) was prepared from the fermented DFSM slurry after a 30 day cultivation at 60 °C and a 60 day ripening at 45 °C. Free amino acid (AA) and organic acid contents in the soy sauce increased in proportion to the fermentation period, whereas ammonium decreased proportionally. Mg and Ca contained in the soy sauce decreased proportionally during fermentation and were lower than those in the non-fermented DFSM extract (control). Spectral absorbance of soy sauce prepared from the fermented DFSM slurry was maximal at 430 nm and increased slightly in proportion to the fermentation period. The aroma and flavor of the test soy sauce were significantly different from those of traditional Korean soy sauce. Conclusively, soy sauce may be prepared directly from the fermented DFSM slurry without meju-preparing process and fermentation period may be a factor for control of soy sauce quality.
RESUMO
Carotenoids produced by non-photosynthetic bacteria protect organisms against lethal photodynamic reactions and scavenge oxygenic radicals. However, the carotenoid produced by Gordonia alkanivorans SKF120101 is coupled to reducing power generation. SKF120101 selectively produces carotenoid under light conditions. The growth yield of SKF120101 cultivated under light conditions was higher than that under dark condition. In the cyclic voltammetry, both upper and lower voltammograms for neutral red (NR) immobilized in intact cells of SKF120101 were not shifted in the condition without external redox sources but were commonly shifted downward by glucose addition and light. Electric current generation in a biofuel cell system (BFCS) catalyzed by harvested cells of SKF120101 was higher under light than dark condition. The ratio of electricity generation to glucose consumption by SKF120101 cultivated in BFCS was higher under light than dark condition. The carotenoid produced by SKF120101 catalyzes production of reducing power from light energy, first evaluated by the electrochemical technique used in this research.
Assuntos
Actinomycetales/metabolismo , Carotenoides/biossíntese , Actinomycetales/química , Actinomycetales/genética , Actinomycetales/efeitos da radiação , Fontes de Energia Bioelétrica , Eletricidade , Glucose/metabolismo , Luz , Oxirredução , FotossínteseRESUMO
Bacterial assimilation of CO2 into stable biomolecules using electrochemical reducing power may be an effective method to reduce atmospheric CO2 without fossil fuel combustion. For the enrichment of the CO2-fixing bacteria using electrochemical reducing power as an energy source, a cylinder-type electrochemical bioreactor with a built-in anode compartment was developed. A graphite felt cathode modified with neutral red (NR-graphite cathode) was used as a solid electron mediator to induce bacterial cells to fix CO2 using electrochemical reducing power. Bacterial CO2 consumption was calculated based on the variation in the ratio of CO2 to N2 in the gas reservoir. CO2 consumed by the bacteria grown in the electrochemical bioreactor (2,000 ml) reached a maximum of approximately 1,500 ml per week. Time-coursed variations in the bacterial community grown with the electrochemical reducing power and CO2 in the mineral-based medium were analyzed via temperature gradient gel electrophoresis (TGGE) of the 16S rDNA variable region. Some of the bacterial community constituents noted at the initial time disappeared completely, but some of them observed as DNA signs at the initial time were clearly enriched in the electrochemical bioreactor during 24 weeks of incubation. Finally, Alcaligenes sp. and Achromobacter sp., which are capable of autotrophically fixing CO2, were enriched to major constituents of the bacterial community in the electrochemical bioreactor.
Assuntos
Bactérias/classificação , Bactérias/crescimento & desenvolvimento , Reatores Biológicos/microbiologia , Dióxido de Carbono/metabolismo , Técnicas Eletroquímicas/instrumentação , Achromobacter/genética , Achromobacter/crescimento & desenvolvimento , Alcaligenes/genética , Alcaligenes/crescimento & desenvolvimento , Bactérias/genética , Biotecnologia/métodos , Meios de Cultura , DNA Bacteriano/análise , DNA Bacteriano/genética , DNA Ribossômico/genética , Eletroforese em Gel de Gradiente Desnaturante , Eletrodos , RNA Ribossômico 16S/genéticaRESUMO
L. lactis sk071115 has been shown to grow more actively and generate lower levels of lactate in glucose-defined medium with nitrate than in medium with Mn(IV). By adding Mn(IV) to a L. lactis culture, lactate production was relatively reduced in combination with Mn(II) production, but cell mass production levels did not increase. Both cell-free extract and intact L. lactis cells reacted electrochemically with Mn(IV) but did not react with Mn(II) upon cyclic voltammetry using neutral red (NR) as an electron mediator. A modified graphite felt cathode with NR (NR-cathode) was employed to induce electrochemical reducing equivalence for bacterial metabolism. Cell-free L. lactis extract catalyzed the reduction of Mn(IV) to Mn(II) under both control and electrochemical reduction conditions; however, the levels of Mn(II) generated under electrochemical reduction conditions were approximately 4 times those generated under control conditions. The levels of Mn(II) generated by the catalysis of L. lactis immobilized in the NR-cathode (L-NR-cathode) under electrochemical reduction conditions were more than 4 times that generated under control conditions. Mn(II) production levels were increased by approximately 2.5 and 4.5 times by the addition of citrate to the reactant under control and electrochemical reduction conditions, respectively. The cumulative Mn(II) produced from manganese ore by catalysis of the L-NR-cathode for 30 days reached levels of approximately 3,800 and 16,000 mg/l under control and electrochemical reduction conditions, respectively. In conclusion, the electrochemical reduction reaction generated by the NR-cathode activated the biochemical reduction of Mn(IV) to Mn(II) by L. lactis.
Assuntos
Eletrodos/microbiologia , Lactococcus lactis/crescimento & desenvolvimento , Lactococcus lactis/metabolismo , Manganês/metabolismo , Fontes de Energia Bioelétrica , Meios de Cultura/química , Vermelho Neutro/metabolismoRESUMO
Three types of nuruk were made from rice, wheat, and a rice-glasswort (6:4) mixture. Nuruk, makgeolli, and vinegar were manufactured with rice nuruk (RN), wheat nuruk (WN), and rice-glasswort nuruk (RGN). The saccharifying activity and ethanol productivity of nuruk, polyphenol content in makgeolli, and acetic acid and polyphenol content in the vinegar were increased as the result of the addition of glasswort. The variable region of 18S- or 16S-rDNA amplified with genomic DNA extracted directly from nuruk, makgeolli- and vinegar-making cultures was analyzed via temperature gradient gel electrophoresis (TGGE). The sequence of the 18S-rDNA variable region extracted from the TGGE gel for nuruk was more than 95% homologous with Aspergillus sp and that for the makgeolli-making culture was more than 95% homologous with Saccharomyces sp and Saccharomycodes sp. The sequence of the 16S-rDNA variable region extracted from TGGE gel for the vinegar-making culture was more than 95% homologous, primarily with the Acetobacter sp. The eukaryotic and prokaryotic diversity in the nuruk, makgeolli-making, and vinegar-making cultures was not significantly altered by the addition of glasswort. Prokaryotic diversity was higher than eukaryotic diversity in the nuruk, but eukaryotic diversity was higher than prokaryotic diversity in the makgeolli-making culture, on the basis of the TGGE patterns. No 18S-rDNA was amplified from the DNA extracted from the vinegar-making culture. In conclusion, the glasswort may be not simply an activator for the growth of microorganisms during the fermentation of nuruk, makgeolli, or vinegar, but also a nutritional supplement that improves the quality of vinegar.
Assuntos
Ácido Acético/metabolismo , Chenopodiaceae/metabolismo , Microbiologia de Alimentos , Ácido Acético/análise , Acetobacter/genética , Acetobacter/isolamento & purificação , Aspergillus/genética , Aspergillus/isolamento & purificação , Fermentação , Oryza/metabolismo , RNA Bacteriano/análise , RNA Fúngico/análise , RNA Ribossômico 16S/análise , RNA Ribossômico 18S/análise , Saccharomyces/genética , Saccharomyces/isolamento & purificação , Triticum/metabolismoRESUMO
Five bacterial species, capable of degrading the recalcitrant organic compounds (ROCs) diethyleneglycol monomethylether (DGMME), 1-amino-2-propanol (APOL), 1-methyl-2- pyrrolidinone (NMP), diethyleneglycol monoethylether (DGMEE), tetraethyleneglycol (TEG), and tetrahydrothiophene 1,1-dioxide (sulfolane), were isolated from an enrichment culture. Cupriavidus sp. catabolized 93.5+/-1.7 mg/l of TEG, 99.3+/-1.2 mg/l of DGMME, 96.1+/-1.6mg/l of APOL, and 99.5+/-0.5mg/l of NMP in 3 days. Acineobacter sp. catabolized 100 mg/l of DGMME, 99.9+/-0.1 mg/l of NMP, and 100 mg/l of DGMEE in 3 days. Pseudomonas sp.3 catabolized 95.7+/-1.2 mg/l of APOL and 99.8+/-0.3 mg/l of NMP. Paracoccus sp. catabolized 98.3+/-0.6 mg/l of DGMME and 98.3+/-1.0 mg/l of DGMEE in 3 days. A maximum 43+/-2.0 mg/l of sulfolane was catabolized by Paracoccus sp. in 3 days. When a mixed culture composed of the five bacterial species was applied to real wastewater containing DGMME, APOL, NMP, DGMEE, or TEG, 92~99% of each individual ROC was catabolized within 3 days. However, at least 9 days were required for the complete mineralization of sulfolane. Bacterial community diversity, analyzed on the basis of the TGGE pattern of 16S rDNA extracted from viable cells, was found to be significantly reduced in a conventional bioreactor after 6 days of incubation. However, biodiversity was maintained after 12 days of incubation in an electrochemical bioreactor. In conclusion, the electrochemical reduction reaction enhanced the diversity of the bacterial community and actively catabolized sulfolane.
Assuntos
Bactérias/química , Bactérias/metabolismo , Biodiversidade , Compostos Orgânicos/metabolismo , Gerenciamento de Resíduos/métodos , Poluentes Químicos da Água/metabolismo , Bactérias/classificação , Bactérias/genética , Biodegradação Ambiental , Reatores Biológicos/microbiologia , DNA Bacteriano/genética , DNA Ribossômico/genética , Eletroquímica , Dados de Sequência Molecular , Oxirredução , RNA Ribossômico 16S/genética , Esgotos/análiseRESUMO
Oxygen has been so far addressed as the most preferable terminal electron acceptor in the cathodes of microbial fuel cells (MFCs). However, to reduce the oxygen reduction overpotential at the cathode surface, eco-unfriendly and costly catalysts have been commonly employed. Here, we pursued the possibility of using a high surface area electrode to reduce the cathodic reaction overpotential rather than the utilization of catalyzed materials. A dual chambered MFC reactor was designed with the use of graphite-granule electrodes and a permeable membrane. The performance of the reactor in terms of electricity generation and organic removal rate was examined under a continuous-feed manner. Results showed that the maximum volumetric power of 4.4+/-0.2 W/m(3) net anodic compartment (NAC) was obtained at a current density of 11+/-0.5 A/m(3) NAC. The power output was improved by increasing the electrolyte ionic strength. An acceptable effluent quality was attained when the organic loading rate (OLR) of 2 kgCOD/m(3) NAC d was applied. The organic removal rate seemed to be less affected by shock loading. Our system can be suggested as a promising approach to make MFC-based technology economically viable for wastewater treatment applications. This study shows that current generation can be remarkably improved in comparison with several other studies using a low-surface-area plain graphite electrode.
Assuntos
Fontes de Energia Bioelétrica , Conservação dos Recursos Naturais , Grafite/química , Eliminação de Resíduos Líquidos , Reatores Biológicos , Eletrodos , Membranas ArtificiaisRESUMO
A modified graphite felt electrode with neutral red (NRelectrode) was shown to catalyze the chemical oxidation of nitrite to nitrate under aerobic conditions. The electrochemically oxidized NR-electrode (EO-NR-electrode) and reduced NR-electrode (ER-NR-electrode) catalyzed the oxidation of 1,094+/-39 mg/l and 382+/-45 mg/l of nitrite, respectively, for 24 h. The electrically uncharged NRelectrode (EU-NR-electrode) catalyzed the oxidation of 345+/-47 mg/l of nitrite for 24 h. The aerobic bacterial community immobilized in the EO-NR-electrode did not oxidize ammonium to nitrite; however, the aerobic bacterial community immobilized in the ER-NR-electrode bioelectrochemically oxidized 1,412+/-39 mg/l of ammonium for 48 h. Meanwhile, the aerobic bacterial community immobilized on the EU-NR-electrode biochemically oxidized 449+/-22 mg/l of ammonium for 48 h. In the continuous culture system, the aerobic bacterial community immobilized on the ER-NR-electrode bioelectrochemically oxidized a minimal 1,337+/-38 mg/l to a maximal 1,480+/-38 mg/l of ammonium to nitrate, and the community immobilized on the EU-NR-electrode biochemically oxidized a minimal 327+/-23 mg/l to a maximal 412+/-26 mg/l of ammonium to nitrate every two days. The bacterial communities cultivated in the ER-NR-electrode and EU-NR-electrode in the continuous culture system were analyzed by TGGE on the 20th and 50th days of incubation. Some ammoniumoxidizing bacteria were enriched on the ER-NR-electrode, but not on the EU-NR-electrode.
Assuntos
Bactérias/metabolismo , Reatores Biológicos/microbiologia , Nitritos/química , Compostos de Amônio Quaternário/química , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/química , Bactérias/genética , DNA Bacteriano/química , DNA Bacteriano/genética , Eletroquímica/métodos , Eletrodos , Eletroforese em Gel de Poliacrilamida , Grafite/química , Nitritos/metabolismo , Oxirredução , Reação em Cadeia da Polimerase , Compostos de Amônio Quaternário/metabolismo , RNA Ribossômico 16S/química , RNA Ribossômico 16S/genética , Poluentes Químicos da Água/metabolismoRESUMO
Zymomonas mobilis was immobilized in a modified graphite felt cathode with neutral red (NR-graphite cathode) and Saccharomyces cerevisiae was cultivated on a platinum plate anode to electrochemically activate ethanol fermentation. Electrochemical redox reaction was induced by 3 approximately 4 volt of electric potential charged to a cathode and an anode. Z. mobilis produced 1.3 approximately 1.5 M of ethanol in the cathode compartment and S. cerevisiae did 1.7 approximately 1.9 M in the anode compartment for 96 hr. The ethanol production by Z. mobilis immobilized in the NR-graphite cathode and S. cerevisiae cultivated on the platinum plate was 1.5 approximately 1.6 times higher than those cultivated in the conventional condition. The electrochemical oxidation potential greatly inhibited ethanol fermentation of Z. mobilis but did not S. cerevisiae. Total soluble protein pattern of Z. mobilis cultivated in the electrochemical oxidation condition was getting simplified in proportion to potential intensity based on SDS-PAGE pattern; however the SDS-PAGE pattern of protein extracted from S. cerevisiae cultivated in both oxidation and reduction condition was not changed. When Z. mobilis culture incubated in the cathode compartment for 24 hr was transferred to S. cerevisiae culture in the anode compartment, 0.8 approximately 0.9 M of ethanol was additionally produced by S. cerevisiae for another 24 hr. Conclusively, total 2.0 approximately 2.1 M of ethanol was produced by the electrochemical redox coupling of Z. mobilis and S. cerevisiae for 48 hr.
Assuntos
Etanol/metabolismo , Saccharomyces cerevisiae/química , Saccharomyces cerevisiae/metabolismo , Zymomonas/química , Zymomonas/metabolismo , Reatores Biológicos/microbiologia , Células Imobilizadas/química , Células Imobilizadas/metabolismo , Técnicas Eletroquímicas , OxirreduçãoRESUMO
A single-compartmented microbial fuel cell composed of a graphite felt anode modified with Neutral Red (NR-anode) and a porous Fe(II)-carbon cathode (FeC-cathode) were compared for electricity generation from Microbacterium sp. and Pseudomonas sp. under identical conditions. Pseudomonas sp. was more than four times the size of Microbacterium sp. based on SEM images. In cyclic voltammetry, the redox reaction between Microbacterium sp and electrode was three times the rate observed between Pseudomonas sp. and the electrode based on the Y-axis (current) variation of cyclic voltammogram. The electric power generated by Microbacterium sp. was approx 3-4 times higher than that with Pseudomonas sp. during incubation for more than 150 days in the fuel cell.
Assuntos
Actinomycetales/fisiologia , Fontes de Energia Bioelétrica/microbiologia , Pseudomonas/fisiologia , Actinomycetales/química , Actinomycetales/citologia , Actinomycetales/metabolismo , Fenômenos Fisiológicos Bacterianos , Eletricidade , Microscopia Eletrônica de Varredura , Oxirredução , Pseudomonas/química , Pseudomonas/citologia , Pseudomonas/metabolismoRESUMO
A noncompartmented microbial fuel cell (NCMFC) composed of a Mn(IV)-carbon plate and a Fe(III)-carbon plate was used for electricity generation from organic wastewater without consumption of external energy. The Fe(III)-carbon plate, coated with a porous ceramic membrane and a semipermeable cellulose acetate film, was used as a cathode, which substituted for the catholyte and cathode. The Mn(IV)-carbon plate was used as an anode without a membrane or film coating. A solar cell connected to the NCMFC activated electricity generation and bacterial consumption of organic matter contained in the wastewater. More than 99 degrees of the organic matter was biochemically oxidized during wastewater flow through the four NCMFC units. A predominant bacterium isolated from the anode surface in both the conventional and the solar cell-linked NCMFC was found to be more than 99 degrees similar to a Mn(II)-oxidizing bacterium and Burkeholderia sp., based on 16S rDNA sequence analysis. The isolate reacted electrochemically with the Mn(IV)-modified anode and produced electricity in the NCMFC. After 90 days of incubation, a bacterial species that was enriched on the Mn(IV)-modified anode surface in all of the NCMFC units was found to be very similar to the initially isolated predominant species by comparing 16S rDNA sequences.
Assuntos
Fontes de Energia Bioelétrica/estatística & dados numéricos , Eletricidade , Eliminação de Resíduos Líquidos , Bactérias/genética , Carbono , Cerâmica , Primers do DNA , Eletroquímica/métodos , Eletrodos , Desenho de Equipamento , Manganês , Microscopia Eletrônica de Varredura , Oxigênio/análiseRESUMO
A denitrification bacterium was isolated from riverbed soil and identified as Ochrobactrum sp., whose specific enzymes for denitrification metabolism were biochemically assayed or confirmed with specific coding genes. The denitrification activity of strain G3-1 was proportional to glucose/nitrate balance, which was consistent with the theoretical balance (0.5). The modified graphite felt cathode with neutral red, which functions as a solid electron mediator, enhanced the electron transfer from electrode to bacterial cell. The porous carbon anode was coated with a ceramic membrane and cellulose acetate film in order to permit the penetration of water molecules from the catholyte to the outside through anode, which functions as an air anode. A non-compartmented electrochemical bioreactor (NCEB) comprised of a solid electron mediator and an air anode was employed for cultivation of G3-1 cells. The intact G3-1 cells were immobilized in the solid electron mediator, by which denitrification activity was greatly increased at the lower glucose/nitrate balance than the theoretical balance (0.5). Metabolic stability of the intact G3-1 cells immobilized in the solid electron mediator was extended to 20 days, even at a glucose/nitrate balance of 0.1.
Assuntos
Reatores Biológicos , Nitratos/metabolismo , Nitrogênio/metabolismo , Ochrobactrum/metabolismo , Técnicas Eletroquímicas , Nitrato Redutase/metabolismo , Nitratos/química , Nitrito Redutases/metabolismo , Nitrogênio/química , Ochrobactrum/genética , Ochrobactrum/crescimento & desenvolvimento , Oxirredução , RNA Ribossômico 16S/análise , RNA Ribossômico 16S/genética , Microbiologia do Solo , Eliminação de Resíduos LíquidosRESUMO
An electrochemical bioreactor (ECB) composed of a cathode compartment and an air anode was used in this study to characterize the ethanol fermentation of Zymomonas mobilis. The cathode and air anode were constructed of modified graphite felt with neutral red (NR) and a modified porous carbon plate with cellulose acetate and porous ceramic membrane, respectively. The air anode operates as a catalyst to generate protons and electrons from water. The growth and ethanol production of Z. mobilis were 50% higher in the ECB than were observed under anoxic nitrogen conditions. Ethanol production by growing cells and the crude enzyme of Z. mobilis were significantly lower under aerobic conditions than under other conditions. The growing cells and crude enzyme of Z. mobilis did not catalyze ethanol production from pyruvate and acetaldehyde. The membrane fraction of crude enzyme catalyzed ethanol production from glucose, but the soluble fraction did not. NADH was oxidized to NAD+ in association with H2O2 reduction, via the catalysis of crude enzyme. Our results suggested that NADH/NAD+ balance may be a critical factor for ethanol producton from glucose in the metabolism of Z. mobilis, and that the metabolic activity of both growing cells and crude enzyme for ethanol fermentation may be induced in the presence of glucose.
Assuntos
Etanol/metabolismo , Fermentação , Zymomonas/metabolismo , Acetaldeído/metabolismo , Reatores Biológicos , Catalase/metabolismo , Glucose/metabolismo , Peróxido de Hidrogênio/metabolismo , Microbiologia Industrial/métodos , NAD/metabolismo , Piruvatos/metabolismo , Zymomonas/crescimento & desenvolvimentoRESUMO
Simultaneous organics removal and nitrification using a novel nitrifying biocathode microbial fuel cell (MFC) reactor were investigated in this study. Remarkably, the introduction of nitrifying biomass into the cathode chamber caused higher voltage outputs than that of MFC operated with the abiotic cathode. Results showed the maximum power density increased 18% when cathode was run under the biotic condition and fed by nitrifying medium with alkalinity/NH4+-N ratio of 8 (26 against 22 mW/m2). The voltage output was not differentiated when NH4+-N concentration was increased from 50 to 100 mg/L under such alkalinity/NH4+-N ratio. However, interestingly, the cell voltage rose significantly when the alkalinity/NH4+-N ratio was decreased to 6. Consequently, the maximum power density increased 68% in compared with the abiotic cathode MFC (37 against 22 mW/m2). Polarization curves demonstrated that both activation and concentration losses were lowered during the period of nitrifying biocathode operation. Ammonium was totally nitrified and mostly converted to nitrate in all cases of the biotic cathode conditions. High COD removal efficiency (98%) was achieved. In light of the results presented here, the application of nitrifying biocathode is not only able to integrate the nitrogen and carbon removal but also to enhance the power generation in MFC system. Our system can be suggested to open up a new feasible way for upgrading and retrofitting the existing wastewater treatment plant by the use of MFC-based technologies.
Assuntos
Fontes de Energia Bioelétrica/microbiologia , Reatores Biológicos , Purificação da Água/instrumentação , Bactérias/metabolismo , Conservação de Recursos Energéticos/métodos , Nitritos/metabolismo , Purificação da Água/métodosRESUMO
A bacterium growing inside yeast cytoplasm was observed by light microscope without staining. The bacterium was separately stained from yeast cell by a fluorescent dye, 4',6-diamidino-2-phenylindole (DAPI). The bacterium actively moved inside yeast cytoplasm and propagated in company with the yeast growth. The bacterium was separated from the yeast cytoplasm by selective disruption of yeast cells and the yeast without the intracellular bacterium (YWOB) was obtained by selective inactivation of bacterial cells. The yeast and the intracellular bacterium were identified as Candida tropicalis and Microbacterium sp., respectively. The length of Microbacterium sp. and C. tropicalis measured with SEM image was smaller than 0.5 microm and was larger than 5 microm, respectively. The yeast with the intracellular bacterium (YWIB) grew in a starch-based medium but the YWOB was not C. tropicalis has neither extracellular nor intracellular saccharification enzyme. Glucose was produced from starch by the extracellular crude enzyme (culture fluid) of Microbacterium sp. YWIB produced significantly more ethanol from glucose than YWOB but did not from starch. Conclusively, C. tropicalis is thought to catabolize starch dependent upon Microbacterium sp. growing in its cytoplasm and furnish stable habitat for the Microbacterium sp.
Assuntos
Actinomycetales/fisiologia , Candida tropicalis/fisiologia , Simbiose , Actinomycetales/classificação , Actinomycetales/citologia , Actinomycetales/metabolismo , Sequência de Bases , Candida tropicalis/classificação , Candida tropicalis/citologia , Candida tropicalis/metabolismo , Citoplasma/microbiologia , DNA Bacteriano/química , DNA Bacteriano/genética , DNA Fúngico/química , DNA Fúngico/genética , DNA Ribossômico/química , DNA Ribossômico/genética , Etanol/metabolismo , Genes de RNAr , Glucose/metabolismo , Microscopia , Microscopia Eletrônica de Varredura , Dados de Sequência Molecular , RNA Bacteriano/genética , RNA Fúngico/genética , RNA Ribossômico 16S/genética , RNA Ribossômico 18S/genética , Análise de Sequência de DNA , Amido/metabolismoRESUMO
Anaerobic digestion sludge was cultivated in an electrochemical bioreactor (ECB) to enrich the hydrogenotrophic methanogens. A modified graphite felt cathode with neutral red (NR-cathode) was charged with electrochemical reducing power generated from a solar cell. The methane and carbon dioxide collected in a Teflon bag from the ECB were more than 80 ml/l of reactant/day and less than 20 ml/l of reactant/day, respectively, whereas the methane and carbon dioxide collected from a conventional bioreactor (CB) was around 40 ml/l of reactant/day, respectively. Moreover, the maximal volume ratios of methane to carbon dioxide (M/C ratio) collected in the Teflon bag from the ECB and CB were 7 and 1, respectively. The most predominant methanogens isolated from the CB on the 20th, 80th, and 150th days of incubation were hydrogenotrophs. The methanogenic diversity analyzed by temperature gradient gel electrophoresis (TGGE) of the 16S rDNA variable region was higher in the ECB than in the CB. The DNA extracted from the TGGE bands was more than 95% homologous with hydrogenotrophic methanogens in the CB. In conclusion, the ECB was demonstrated as a useful system for enriching hydrogenotrophic methanogens and increasing the M/C ratio of the gas product.
Assuntos
Reatores Biológicos , Euryarchaeota/crescimento & desenvolvimento , Metano/biossíntese , Biodiversidade , Dióxido de Carbono/metabolismo , DNA Bacteriano/análise , DNA Bacteriano/genética , Técnicas Eletroquímicas , Eletrodos , Euryarchaeota/genética , Euryarchaeota/metabolismo , Hidrogênio/metabolismo , Methanobacteriaceae/genética , Methanobacteriaceae/crescimento & desenvolvimento , Methanobacteriaceae/metabolismo , Methanomicrobiales/genética , Methanomicrobiales/crescimento & desenvolvimento , Methanomicrobiales/metabolismo , Methanosarcinaceae/genética , Methanosarcinaceae/crescimento & desenvolvimento , Methanosarcinaceae/metabolismo , Oxirredução , RNA Ribossômico 16S/análise , RNA Ribossômico 16S/genética , Esgotos/microbiologiaRESUMO
Weissella hellenica SKkimchi3 produces the higher exopolysaccharide (EPS) on sucrose than lactose, glucose, and fructose at pH 5 and 20 degrees C. Sucrose was exclusively used to cultivate SKkimchi3 in all experiments base on the EPS production tests. The molecular mass of EPS, as determined by gel permeation chroma-tography, was 203,000. (1)H and (13)C NMR analysis indicated that the identity of EPS may be a glucan. When EPS, starch, and cellulose was treated with a-amylase, glucoamylase, glucosidase, and cellulase, glucose was produced from starch and cellulose but was not produced from EPS. Based on HPLC analysis, elemental analysis, (1)H and (13)C NMR analysis, and enzymatic hydrolysis tests, EPS was estimated to be a glucan. EPS suspension was not precipitated even by centrifugation at 10,000xg for 60 min, and EPS made the fermented milk and bacterial culture viscous.
Assuntos
Brassica/microbiologia , Fermentação , Microbiologia de Alimentos , Bacilos Gram-Positivos Formadores de Endosporo/metabolismo , Polissacarídeos Bacterianos/química , Brassica/metabolismo , Bacilos Gram-Positivos Formadores de Endosporo/química , Bacilos Gram-Positivos Formadores de Endosporo/classificação , Bacilos Gram-Positivos Formadores de Endosporo/isolamento & purificação , Hidrólise , Coreia (Geográfico) , Lactose/metabolismo , Dados de Sequência Molecular , Peso Molecular , Polissacarídeos Bacterianos/metabolismoRESUMO
When cultivated aerobically, Aspergillus niger hyphae produced extracellular glucoamylase, which catalyzes the saccharification of unliquified potato starch into glucose, but not when grown under anaerobic conditions. The Km and Vmax of the extracellular glucoamylase were 652.3 mg starch l-1 and 253.3 mg glucose l-1 min-1, respectively. In mixed culture of A. niger and Saccharomyces cerevisiae, oxygen had a negative influence on the alcohol fermentation of yeast, but activated fungal growth. Therefore, oxygen is a critical factor for ethanol production in the mixed culture, and its generation through electrolysis of water in an electrochemical bioreactor needs to be optimized for ethanol production from starch by coculture of fungal hyphae and yeast cells. By applying pulsed electric fields (PEF) into the electrochemical bioreactor, ethanol production from starch improved significantly: Ethanol produced from 50 g potato starch l-1 by a mixed culture of A. niger and S. cerevisiae was about 5 g l-1 in a conventional bioreactor, but was 9 g l-1 in 5 volts of PEF and about 19 g l-1 in 4 volts of PEF for 5 days.