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Utilização de culturas mistas como estratégia para estimular a biossíntese de produtos naturais por fungos endofíticos; Utilization of mixed cultures as a strategy to stimulate the biosynthesis of natural products by endophytic fungi

Chagas, Fernanda Oliveira das
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 12/03/2010 PT
Relevância na Pesquisa
56.32%
O estudo das interações planta-microrganismos tem sido de grande interesse ao longo dos últimos anos. Atualmente, as interações que ocorrem entre microrganismos que vivem em estreita relação também vêm merecendo grande atenção, pois forças competitivas e mutualísticas podem induzir a produção de novos metabólitos bioativos. Portanto, estudar interações existentes entre os microrganismos endofíticos que colonizam uma mesma planta parece ser uma estratégia promissora para a obtenção de substâncias quimicamente diferentes, eventualmente bioativas. Através da utilização de culturas mistas de microrganismos, o presente trabalho contribuiu para o conhecimento da relação existente entre os fungos endofíticos SS13 (Papulaspora immersa), SS50 (Fusarium oxysporum), SS67 (Nigrospora sphaerica), SS77 (Alternaria tenuissima) e SS84 (Phoma betae), isolados da planta medicinal Smallanthus sonchifolius (yacon), e sua implicação no aumento da diversidade química de produtos naturais microbianos, com o intuito de se identificar metabólitos secundários anticancerígenos. Para isso, os fungos foram cultivados em culturas singles e mistas em meios de cultivo líquidos e semi-sólidos. Foram utilizados diferentes meios de cultura...

Cultura mista, manipulação química e genética de micro-organismos: estratégias para a diversificação do metabolismo secundário; Mixed culture, chemical and genetic manipulation of microorganisms:strategies for diversifying the secondary metabolism.

Chagas, Fernanda Oliveira das
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 24/04/2014 PT
Relevância na Pesquisa
46.26%
Recentes estudos genômicos têm mostrado que vários fungos e bactérias possuem um potencial biossintético superior à quantidade de me tabólitos secundários já isolados desses micro-organismos. A descoberta de produtos naturais inéditos e bioativos é limitada pela impossibilidade dos micro-organismos expressarem to das as suas rotas biossintéticas em laboratório. Assim, estratégias alternativas para i nduzir a produção de produtos naturais microbianos são necessárias. A utilização de cultur as mistas de micro-organismos é uma estratégia que vem sendo recentemente utilizada, na tentativa de mimetizar condições mais naturais de crescimento. Além disso, a adição de mo duladores químicos e epigenéticos às culturas microbianas também pode potencialmente est imular a produção de compostos de interesse, seja por ativar mecanismos celulares em resposta à condição de estresse, ou por alterar a taxa de transcrição de certos genes, em f unção de mudanças no grau de enovelamento da cromatina. Alternativamente, a indu ção de certos genes, e até mesmo a diversificação do metabolismo secundário, podem ser conseguidos através de engenharia genética, pela manipulação direta de genes de inter esse. A linhagem endofítica Alternaria tenuissima SS77...

Effect of arabinose concentration on dark fermentation hydrogen production using different mixed cultures

Danko, Anthony S.; Abreu, A. A.; Alves, M. M.
Fonte: International Association for Hydrogen Energy Publicador: International Association for Hydrogen Energy
Tipo: Artigo de Revista Científica
Publicado em /09/2008 ENG
Relevância na Pesquisa
46.05%
Dark fermentation hydrogen production from arabinose at concentrations ranging between 0 and 100 g/L was examined in batch assays for three different mixed anaerobic cultures, two suspended sludges (S1, S2) obtained from two different sludge digesters and one granular sludge (G) obtained from a brewery wastewater treatment plant. After elimination of the methanogenic activity by heat treatment, all mixed cultures produced hydrogen, and optimal hydrogen rates and yields were generally observed for concentrations between 10 and 40 g/L of substrate. Higher concentrations of arabinose up to 100 g/L inhibited hydrogen production, although the effect was different from inoculum to inoculum. It was evident that the granular biomass was less affected by increased initial arabinose concentrations when calculating the rate of decrease in hydrogen yields versus arabinose concentrations, compared against the two suspended sludges. The largest amount of soluble microbial product produced for all three inocula was for n-butyrate. Also, valeric acid production was observed in some samples.; Fundação para a Ciência e a Tecnologia (FCT)

Polyhydroxyalkanoate granules quantification in mixed microbial cultures : Sudan Black B versus Nile Blue A staining

Mesquita, D. P.; Amaral, A. L.; Ferreira, E. C.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em 09/06/2014 ENG
Relevância na Pesquisa
66%
Polyhydroxyalkanoates (PHAs) are intracellular granules found in a wide variety of microorganisms under limited nutrient conditions when carbon source is available in excess. These polymers, usually from lipid nature, are used as carbon and energy sources for metabolic synthesis and growth. Despite the important role of PHAs in cell physiology, they are regarded as potential substitutes of traditional petrochemical plastics with the additional advantage of being completely biodegradable and produced from mixed microbial cultures (MMC). PHA quantification is regularly accomplished using a digestion step prior to chromatography analysis which is a labor and time-consuming technique. To overcome these limitations in polymers quantification, the present work investigates two methods for PHA granules identification based on quantitative image analysis (QIA) procedures in an enhanced biological phosphorus removal (EBPR) system operated for three months. MMC were analyzed for PHA granules detection by Sudan Black B (SBB) and Nile Blue A (NBA) staining using bright-field and epifluorescence microscopy, respectively. The captured color images were evaluated through QIA and the image analysis data was further processed using multivariate statistical analysis. Quite satisfactory partial least squares (PLS) regressions (R2) of 0.85 for NBA and 0.86 for SBB were established between PHA concentrations predicted from QIA parameters and determined by the standard analytical method. Although SBB staining procedure was found to provide a somewhat higher estimation of PHA concentrations in MMC...

Polyhydroxyalkanoate granules quantification in mixed microbial cultures using image analysis: Sudan Black B versus Nile Blue A staining

Mesquita, D. P.; Amaral, A. L.; Leal, C.; Oehmen, Adrian; Reis, Maria A. M.; Ferreira, E. C.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em 20/03/2015 ENG
Relevância na Pesquisa
96.14%
Polyhydroxyalkanoates (PHA) can be produced and intracellularly accumulated as inclusions by mixed microbial cultures (MMC) for bioplastic production and in enhanced biological phosphorus removal (EBPR) systems. Classical methods for PHA quantification use a digestion step prior to chromatography analysis, rendering them labor intensive and time-consuming. The present work investigates the use of two quantitative image analysis (QIA) procedures specifically developed for PHA inclusions identification and quantification. MMC obtained from an EBPR system were visualized by bright-field and fluorescence microscopy for PHA inclusions detection, upon Sudan Black B (SBB) and Nile Blue A (NBA) staining, respectively. The captured color images were processed by QIA techniques and the image analysis data were further treated using multivariate statistical analysis. Partial least squares (PLS) regression coefficients of 0.90 and 0.86 were obtained between QIA parameters and PHA concentrations using SBB and NBA, respectively. It was found that both staining procedures might be seen as alternative methodologies to classical PHA determination.

Food waste valorization through the production of polyhydroxyalkanoates by mixed microbial cultures

Carmo, Inês Miguel Troles Duarte do
Fonte: Faculdade de Ciências e Tecnologia Publicador: Faculdade de Ciências e Tecnologia
Tipo: Dissertação de Mestrado
Publicado em //2013 ENG
Relevância na Pesquisa
96.25%
Dissertação para obtenção do Grau de Mestre em Engenharia Química e Bioquímica; Polyhydroxyalkanoates (PHAs) are polyesters of hydroxyl fatty acids, which are accumulated in microbial cells as carbon/energy reserves. PHAs are bio-based and biodegradable and display a wide range of thermoplastic properties, being a promising alternative to conventional plastics. Presently, industrial PHA production was primarily based on pure microbial cultures. Although this process has high PHA production efficiency, it presents high costs associated with the use of chemically-defined feedstocks, and to the need for sterility. An attractive feature of mixed microbial cultures (MMCs) PHAs production is the ability to use waste/surplus feedstocks. Many industrial wastes are seasonally produced making it necessary find the best method of utilization of this feedstock on PHA production process. Two different approaches might be taken account: (1) stock of industrial wastes during their production for their use throughout the year. However, the high fermentability of these agro-industrial wastes makes them susceptible to degradation during storage period; (2) the use of different feedstocks over the year according its availability. It is thus important to study MMC’s response to different feedstocks. The aim of this work is study how MMC PHA production process is affected by a feedstock shift...

Investigation of the regulation mechanisms for bioplastics production from industrial residues

Pedras, Maria Inês Machado
Fonte: Faculdade de Ciências e Tecnologia Publicador: Faculdade de Ciências e Tecnologia
Tipo: Dissertação de Mestrado
Publicado em //2013 ENG
Relevância na Pesquisa
46%
Dissertação para obtenção do Grau de Mestre em Biotecnologia; The current high demand for plastics has become unsustainable. Polyhydroxyalkanoates are biopolymers stored by bacteria that can potentially replace modern plastics due to: wide range of applications; biodegradability; use of renewable resources as feedstock. High costs of current Polyhydroxyalkanoates production can be reduced using mixed cultures of organisms. Activated sludge from wastewater treatment plants is selected for Polyhydroxyalkanoates production through the imposition of cycles of intermittent feeding. In this study, the acclimation of activated sludge using synthetic volatile fatty acids (VFAs) as substrate resulted in a culture rich in Paracoccus spp. and unidentified filamentous bacteria. Low cost substrates such as sugarcane molasses (SM) or cheese whey (CW) can be employed as feedstock for further cost reduction. This requires an additional step before the microbial selection to ferment the feedstock into VFAs. In this work, the feedstock was changed from SM to CW. The population fed with SM was rich in Actinomycetaceae, while the population fed with CW was rich in Streptococcaceae, affecting the VFA composition. Consequently, the PHA-storing population and the polymer were affected. In the fermented SM (fSM) phase...

Constraint-based modelling of mixed microbial populations: Application to polyhydroxyalkanoates production

Pardelha, Filipa Alexandra Guerreiro
Fonte: Faculdade de Ciências e Tecnologia Publicador: Faculdade de Ciências e Tecnologia
Tipo: Tese de Doutorado
Publicado em //2013 ENG
Relevância na Pesquisa
76%
Dissertação para obtenção do Grau de Doutor em Engenharia Química e Bioquímica; The combined use of mixed microbial cultures (MMC) and fermented feedstock as substrate may significantly decrease polyhydroxyalkanoates (PHA) production costs and make them more competitive in relation to conventional petroleum-based polymers. However, there still exists a lack of knowledge at metabolic level that limits the development of strategies to make this process more effective. In this thesis, system biology computational tools were developed and applied to PHA production by MMC from fermented sugar cane molasses, rich in volatile fatty acids (VFA). Firstly, a metabolic network able to describe the uptake of complex mixtures of VFA and PHA production was defined. This metabolic network was applied to metabolic flux analysis (MFA) to describe substrate uptake and PHA production fluxes over the enrichment time of a culture submitted to the feast and famine regimen. Then, the minimization of the tricarboxylic acid cycle (TCA) fluxes was identified as the key metabolic objective of a MMC subjected to this regimen by flux balance analysis (FBA). This model enabled to predict, with an acceptable accuracy, the PHA fluxes and biopolymer composition. Subsequently...

Microbial contribution to biofuels production

Fidalgo, Ana Rita Fernandes Ribeiro Moita
Fonte: Faculdade de Ciências e Tecnologia Publicador: Faculdade de Ciências e Tecnologia
Tipo: Tese de Doutorado
Publicado em //2014 ENG
Relevância na Pesquisa
76.16%
Dissertação para obtenção do Grau de Doutor em Engenharia Química e Bioquímica; Biomass can be converted into biofuels by two different ways: thermochemical or biochemical. Both processes produce waste streams that can be valorised in order to increase the sustainability of the biofuels production process. Recent research on polyhydroxyalkanoates(PHA) production has focused on developing cost-effective processes using low cost substrates combined with mixed microbial cultures (MMC). The intent of this thesis was to study and characterise MMC able to produce PHA using the by-products resulting from the biofuels production. Bio-oil resulting from the fast-pyrolysis of chicken beds was used as substrate to select cultures under feast/famine conditions with a good PHA storage response. Several operational conditions were investigated and optimized. A copolymer composed by hydroxybutyrate and hydroxyvalerate monomers (70%:30%) was obtained. The impact of the bio-oil matrix on PHA production was also investigated suggesting that some compound may inhibit or interfere with the ability of the enriched culture to accumulate PHA. For further maximization of polymer accumulation two strategies for bio-oil upgrade were performed, anaerobic fermentation and vacuum distillation. The increased of volatile fatty acids on the fermented bio-oil led to an increase on the production yield compared to the ones obtain with pure bio-oil (0.63 and 0.31Cmmol HA/Cmmol S...

Mixed Cultures Fermentation for the Production of Poly- ß-hydroxybutyrate

Shalin,Thomas; Sindhu,Raveendran; Binod,Parameswaran; Soccol,Carlos Ricardo; Pandey,Ashok
Fonte: Instituto de Tecnologia do Paraná - Tecpar Publicador: Instituto de Tecnologia do Paraná - Tecpar
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2014 EN
Relevância na Pesquisa
56.09%
Poly-ß-hydroxybutyrate (PHB) is a biodegradable intracellular microbial product produced by many bacteria and it is comparable to some of the petrochemical derived thermoplastics such as polypropylene. One of the main barriers for the commercial exploitation is the high cost of the substrate for the production of biopolymer. The utilization of mixed microbial cultures facilitates the use of complex substrates thereby reducing the cost of PHB production. In the present study, mixed culture systems were evaluated for PHB production. Bacillus firmus NII 0830 was used for the production of PHB since it accumulates a large amount of PHB and a second organism Lactobacillus delbrueckii NII 0925 was used to provide lactic acid. FTIR and 1H NMR analyses revealed that the PHB extracted from pure culture and mixed culture showed exact match to that of standard PHB. Biodegradation studies of the PHB blends showed 87% degradation. It was also found that a consortium of organisms degraded the films faster than a single organism.

Volatile Compounds Originating from Mixed Microbial Cultures on Building Materials under Various Humidity Conditions

Korpi, Anne; Pasanen, Anna-Liisa; Pasanen, Pertti
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /08/1998 EN
Relevância na Pesquisa
66.13%
We examined growth of mixed microbial cultures (13 fungal species and one actinomycete species) and production of volatile compounds (VOCs) in typical building materials in outside walls, separating walls, and bathroom floors at various relative humidities (RHs) of air. Air samples from incubation chambers were adsorbed on Tenax TA and dinitrophenylhydrazine cartridges and were analyzed by thermal desorption-gas chromatography and high-performance liquid chromatography, respectively. Metabolic activity was measured by determining CO2 production, and microbial concentrations were determined by a dilution plate method. At 80 to 82% RH, CO2 production did not indicate that microbial activity occurred, and only 10% of the spores germinated, while slight increases in the concentrations of some VOCs were detected. All of the parameters showed that microbial activity occurred at 90 to 99% RH. The microbiological analyses revealed weak microbial growth even under drying conditions (32 to 33% RH). The main VOCs produced on the building materials studied were 3-methyl-1-butanol, 1-pentanol, 1-hexanol, and 1-octen-3-ol. In some cases fungal growth decreased aldehyde emissions. We found that various VOCs accompany microbial activity but that no single VOC is a reliable indicator of biocontamination in building materials.

Monitoring Gene Expression in Mixed Microbial Communities by Using DNA Microarrays

Dennis, Philip; Edwards, Elizabeth A.; Liss, Steven N.; Fulthorpe, Roberta
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /02/2003 EN
Relevância na Pesquisa
46.03%
A DNA microarray to monitor the expression of bacterial metabolic genes within mixed microbial communities was designed and tested. Total RNA was extracted from pure and mixed cultures containing the 2,4-dichlorophenoxyacetic acid (2,4-D)-degrading bacterium Ralstonia eutropha JMP134, and the inducing agent 2,4-D. Induction of the 2,4-D catabolic genes present in this organism was readily detected 4, 7, and 24 h after the addition of 2,4-D. This strain was diluted into a constructed mixed microbial community derived from a laboratory scale sequencing batch reactor. Induction of two of five 2,4-D catabolic genes (tfdA and tfdC) from populations of JMP134 as low as 105 cells/ml was clearly detected against a background of 108 cells/ml. Induction of two others (tfdB and tfdE) was detected from populations of 106 cells/ml in the same background; however, the last gene, tfdF, showed no significant induction due to high variability. In another experiment, the induction of resin acid degradative genes was statistically detectable in sludge-fed pulp mill effluent exposed to dehydroabietic acid in batch experiments. We conclude that microarrays will be useful tools for the detection of bacterial gene expression in wastewaters and other complex systems.

Bacterial Growth in Mixed Cultures on Dissolved Organic Carbon from Humic and Clear Waters

Tranvik, Lars J.; Höfle, Manfred G.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /03/1987 EN
Relevância na Pesquisa
46.04%
Interactions between bacterial assemblages and dissolved organic carbon (DOC) from different sources were investigated. Mixed batch cultures were set up with water from a humic and a clear-water lake by a 1:20 dilution of the bacterial assemblage (1.0 μm of prefiltered lake water) with natural medium (sterile filtered lake water) in all four possible combinations of the two waters and their bacterial assemblages. Bacterial numbers and biomass, DOC, thymidine incorporation, ATP, and uptake of glucose and phenol were followed in these cultures. Growth curves and exponential growth rates were similar in all cultures, regardless of inoculum or medium. However, bacterial biomass produced was double in cultures based on water from the humic lake. The fraction of DOC consumed by heterotrophic bacteria during growth was in the same range, 15 to 22% of the total DOC pool, in all cultures. Bacterial growth efficiency, calculated from bacterial biomass produced and DOC consumed, was in the order of 20%. Glucose uptake reached a peak during exponential growth in all cultures. Phenol uptake was insignificant in the cultures based on the clear-water medium, but occurred in humic medium cultures after exponential growth. The similarity in the carbon budgets of all cultures indicated that the source of the bacterial assemblage did not have a significant effect on the overall carbon flux. However...

Degradation of polychlorinated biphenyls by mixed microbial cultures.

Clark, R R; Chian, E S; Griffin, R A
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /04/1979 EN
Relevância na Pesquisa
46.07%
Three different enriched mixed cultures capable of degrading polychlorinated biphenylas were isolated from two soil samples and a river sediment, respectively. The predominant organisms found in all three mixed cultures were Alcaligenes odorans, Alcaligenes dentrificans, and an unidentified bacterium. The polychlorinated biphenyl isomers that were more water soluble and had lower chlorination were not only degraded at a faster rate than those that were less water soluble and had higher chlorination, but were also more completely utilized by these mixed cultures. This resulted in the presence in the environment of polychlorinated biphenyl residues consisting mainly of higher-chlorinated isomers. A form of cometabolism of polychlorinated biphenyls was also found with these cultures in the presence of acetate as the cosubstrate.

Effects of propicillin on mixed continuous cultures of periodontal bacteria.

van der Hoeven, J S; van den Kieboom, C W
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /09/1991 EN
Relevância na Pesquisa
46.02%
Experiments were designed to test the antibiotic (1-phenoxypropyl)penicillin (propicillin) against a complex microflora of periodontal bacteria. This was accomplished by using a continuously growing mixed culture that was obtained by enrichment of periodontal plaque in human serum. Peptostreptococcus species, Prevotella intermedia, Lactobacillus, catenaforme, and Streptococcus species were dominant members of the enrichment culture. None of the strains isolated from the enrichment culture exhibited detectable beta-lactamase activity. MICs of propicillin for the organisms ranged from 0.1 to 1.2 mg/liter. Propicillin was added to the cultures in single doses that were repeated once or twice at 24-h intervals, that is, after 2.4 volume changes of the culture vessel. Analyses done 24 h after the last addition of propicillin revealed that total cell counts of the culture were hardly affected by 1 mg of propicillin per liter, although some changes in the microbial composition occurred. The relative insusceptibility of the culture might be explained by the low growth rate. Higher concentrations (5, 10, and 50 mg/liter) of the antibiotic caused 10- to 20-fold drops in total cell counts. In these cultures P. intermedia was selectively suppressed to below the detection level...

The impact of oxygen on the final alcohol content of wine fermented by a mixed starter culture

Morales, Pilar; Rojas, Virginia; Quirós, Manuel; Gonzalez, Ramon
Fonte: Springer Berlin Heidelberg Publicador: Springer Berlin Heidelberg
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.1%
We have developed a wine fermentation procedure that takes advantage of the metabolic features of a previously characterized Metschnikowia pulcherrima strain in order to reduce ethanol production. It involves the use of M. pulcherrima/Saccharomyces cerevisiae mixed cultures, controlled oxygenation conditions during the first 48 h of fermentation, and anaerobic conditions thereafter. The influence of different oxygenation regimes and initial inoculum composition on yeast physiology and final ethanol content was studied. The impact of oxygenation on yeast physiology goes beyond the first aerated step and influences yields and survival rates during the anaerobic stage. The activity of M. pulcherrima in mixed oxygenated cultures resulted in a clear reduction in ethanol yield, as compared to S. cerevisiae. Despite relatively low initial cell numbers, S. cerevisiae always predominated in mixed cultures by the end of the fermentation process. Strain replacement was faster under low oxygenation levels. M. pulcherrima confers an additional advantage in terms of dissolved oxygen, which drops to zero after a few hours of culture, even under highly aerated conditions, and this holds true for mixed cultures. Alcohol reduction values about 3.7 % (v/v) were obtained for mixed cultures under high aeration...

Comparison of Different Strategies for Selection/Adaptation of Mixed Microbial Cultures Able to Ferment Crude Glycerol Derived from Second-Generation Biodiesel

Varrone, C.; Heggeset, T. M. B.; Le, S. B.; Haugen, T.; Markussen, S.; Skiadas, I. V.; Gavala, H. N.
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
66.05%
Objective of this study was the selection and adaptation of mixed microbial cultures (MMCs), able to ferment crude glycerol generated from animal fat-based biodiesel and produce building-blocks and green chemicals. Various adaptation strategies have been investigated for the enrichment of suitable and stable MMC, trying to overcome inhibition problems and enhance substrate degradation efficiency, as well as generation of soluble fermentation products. Repeated transfers in small batches and fed-batch conditions have been applied, comparing the use of different inoculum, growth media, and Kinetic Control. The adaptation of activated sludge inoculum was performed successfully and continued unhindered for several months. The best results showed a substrate degradation efficiency of almost 100% (about 10 g/L glycerol in 21 h) and different dominant metabolic products were obtained, depending on the selection strategy (mainly 1,3-propanediol, ethanol, or butyrate). On the other hand, anaerobic sludge exhibited inactivation after a few transfers. To circumvent this problem, fed-batch mode was used as an alternative adaptation strategy, which led to effective substrate degradation and high 1,3-propanediol and butyrate production. Changes in microbial composition were monitored by means of Next Generation Sequencing...

Study of acidogenic fermentation conditions for VFAs production; Estudo de condições de fermentação acidogénica para a produção de AOVs

Cruz, Rafaela Alexandra Palma
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Dissertação de Mestrado
ENG
Relevância na Pesquisa
66%
The acidogenic fermentation is the second phase of anaerobic digestion. Volatile fatty acids (VFAs) are the main products of acidogenic fermentation and can act as substrates for hydrogen or polyhydroxyalkanoates (PHA) production. In this work, mixed microbial cultures (MMC) collected in a wastewater treatment plants were used for acidogenic fermentation of hardwood spent sulphite liquor (HSSL), a by-product of paper and pulp industry, in a continuously stirred tank reactor (CSTR), and cheese whey permeate (CWP) in a sequential batch reactor (SBR) in non-sterile conditions. In HSSL fermentation, HRT of 1.6 and 2 days were tested with a feeding concentration of 15 g COD/L. pH was left uncontrolled, but was stable around 5.0 ± 0.24 due to the buffer effect of HSSL. The highest conversion of 10 %, with 68% of sugars, and degree of acidification of 10 % were obtained at HRT 2 days and OLR of 7.7 g COD/(L·d). By using CWP a high conversion of acidogenic fermentation (> 80 %) was achieved, even at a pH below the optimal value (4.5). pH and HRT influenced sugars to VFA conversion and the profile of products. Conversion improved with pH and HRT and ethanol-type and propionic-type fermentation were identified at different pHs. Finally from the conditions tested for acidogenic fermentation of CWP...

Impact of carbon/nitrogen feeding strategy on polyhydroxyalkanoates production using mixed microbial cultures

Silva, Fernando Ramos
Fonte: Universidade Nova de Lisboa Publicador: Universidade Nova de Lisboa
Tipo: Dissertação de Mestrado
Publicado em /12/2015 ENG
Relevância na Pesquisa
96.19%
Polyhydroxyalkanoates (PHA) production using mixed microbial cultures (MMC) requires a multi-stage process involving the microbial selection of PHA-storing microorganisms, typically operated in sequencing batch reactors (SBR), and an accumulation reactor. Since low-cost renewable feedstocks used as process feedstock are often nitrogen-deficient, nutrient supply in the selection stage is required to allow for microbial growth. In this context, the possibility to uncouple nitrogen supply from carbon feeding within the SBR cycle has been investigated in this study. Moreover, three different COD:N ratios (100:3.79, 100:3.03 and 100:2.43) were tested in three different runs which also allowed the study of COD:N ratio on the SBR performance. For each run, a synthetic mixture of acetic and propionic acids at an overall organic load rate of 8.5 gCOD L-1 d-1 was used as carbon feedstock, whereas ammonium sulfate was the nitrogen source in a lab-scale sequence batch reactor (SBR) with 1 L of working volume. Besides, a sludge retention time (SRT) of 1 d was used as well as a 6 h cycle length. The uncoupled feeding strategy significantly enhanced the selective pressure towards PHA-storing microorganisms, resulting in a two-fold increase in the PHA production (up to about 1.3 gCOD L-1). A high storage response was observed for the two runs with the COD:N ratios (gCOD:gN) of 100:3.79 and 100:3.03...

Effects of residues on the degradation of PHA produced from mixed microbial cultures and processed in extrusion

Hilliou, L.; Teixeira, P. F.; Machado, Diogo Silva; Covas, J. A.; Oliveira, Catarina S. S.; Gouveia, Ana; Reis, Maria A.M.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em //2015 ENG
Relevância na Pesquisa
66%
Thermal degradation upon melting is one of the major drawbacks reported for polyhydroxyalkanoates (PHA). However, the role of residues originating from the fermentation and the extraction steps on the thermal stability of this class of biopolymers still needs to be clarified. In the particular case of PHA produced from mixed microbial cultures (MMC), this topic is even less documented in the literature. Here, two polyhydroxy(butyrate-co-valerate) (PHBV) produced from MMC enriched in PHA accumulating organisms and fed with cheese whey were studied. A micro extrusion line is used to produce filaments and assess the processability and the degradation of processed PHBV. The prototype micro extrusion line allows for studying grams of materials. The two PHBV contain 18 mol% HV. PHBV was recovered with 11 wt% residues, and further submitted to a purification procedure resulting in a second biopolyester containing less than 2 wt% impurities. The thermorheological characterization of the two PHBV is first presented, together with their semicrystalline properties. Then the processing windows of the two biopolyesters are presented. Finally, the properties of extruded filaments are reported and the thermomechanical degradation of PHBV is extensively studied. The structure was assessed by wide angle X-ray diffraction...