Loss of nitrogen (N) from dairy manure during storage is an issue of economic, environmental, and social concern for farming communities. The lost N 1) decreases the value of manure as a fertilizer and is an economic loss because supplemental inorganic N fertilizer is purchased to meet N needs on farms; 2) produces the potential pollution for water and air systems, thereby damaging the associated ecosystems; 3) causes challenges to human health. Thus, it is vital to manage and use N in an efficient and eco-friendly manner. N mineralization is a pathway in the N cycle, which converts organic N to inorganic N that is more susceptible to loss. The objective of this study was to conduct lab-scale experiments to assess the effects of temperature, manure solids content, using manure seed and autoclave sterilization operation at the start of storage, and storage time on the N mineralization and the associated microbial community during the storage of liquid dairy manure. Manure scrapped from the barn floor of a commercial dairy farm and diluted to make experimental stocks with high (46 to 78 g/L) and low (19 to 36 g/L) total solids (TS), to simulate what is typically transported to the manure storage pit was used. The manure was incubated in the laboratory at three temperatures (10, 20, and 30°C) for two storage periods (60 and 180 days). Manure samples were taken at different storage time for analyses. The results showed that temperature and using sterilization operation at the start of storage had significant effects on N mineralization for both storage periods (p < 0.05). The highest N mineralization rate occurred at 30℃, which rate constant (k) was 0.096 week-1. While, the lowest N mineralization occurred at 10℃, and its corresponding k was 0.013 week-1. The concentrations of mineralized N (Nm) with non-sterilized (R) manure were significantly higher than that with sterilized (R0) manure (p < 0.05). Compared to that with high TS (H) manure, the concentrations of Nm were significantly higher with low TS (L) manure after 180-d storage (p < 0.05). Raw manure augmented with manure seed (MS) had significantly higher Nm than the manure seed only (SO) (p < 0.05). In order to investigate the changes of microbial community in manure, samples were collected on days 0, 30, 90, and 180 for the 180-d storage experiment, and days 0, 30, and 60 for the 60-d storage experiment, and then manure DNA under different condition was successfully extracted from collected samples and used for 16S rRNA sequencing. This study provided a more comprehensive understanding of the impact factors for manure storage, and was expected to clarify the relationship between N mineralization and the associated microbial community. / Master of Science / Loss of nitrogen (N) from dairy manure during storage is rooted in the process of degradation via microbial activities. During storage of dairy manure, up to 60% of N can be lost to the environment (the air, rivers, groundwater, etc.), causing damages such as global warming and water pollution. However, it is challenging to manage and reduce the N lost during manure storage because of lack of comprehensive knowledge of the complex microbial activities in manure storage structures. Thus, the long-term goal of this study is to discern the interactions of the physical, chemical, and microbial processes that affect the N transformation. The generated information will help to mitigate/minimize the loss of nitrogenous gases during storage of dairy manure. The specific objectives included: 1) to evaluate the effects of selected factors (including storage time, temperature, manure solids content, using manure seed and sterilization operation at the beginning of storage) on N mineralization during storage of liquid dairy manure and determine the associated N mineralization rate; 2) to reveal the microbial communities in stored liquid dairy manure under different conditions (listed above). The outcome of this study could be used to refine N mineralization input parameter of manure storage submodules of the process-based models such as Manure DeNitrification-DeComposition model (Manure-DNDC) and Integrated Farm System Model (IFSM) with the goal to improve their accuracy of estimating or accounting for the fate or cycling of N in dairy manure during storage.

Com as limitações para cultivar os micro-organismos, tornou-se necessário caracterizar molecularmente os recursos genéticos microbianos. Entretanto, como estes estudos são realizados através do DNA, podemos encontrar distintos resultados dependendo da metodologia de extração de DNA utilizada. Assim, essa pesquisa buscou aperfeiçoar uma técnica para extrair DNA de água do e para demonstrar a importância dos métodos de extração de DNA no estudo dos micro-organismos por métodos independentes de cultivo, foi caracterizada, através da técnica de DGGE, a diversidade de uma comunidade bacteriana marinha usando diferentes métodos de extração de DNA. O aperfeiçoamento da metodologia de extração de DNA de água do mar resultou em um protocolo com a qualidade do DNA similar à do protocolo original, com rendimento melhor e aproximadamente quatro vezes mais rápido. Em relação à caracterização, verificamos, pelo DGGE, distintos perfis da comunidade microbiana marinha, tanto em relação à presença e ausência das bandas de DNA, como em relação à sua intensidade. / With the limitations of microorganisms culture techniques, it has become necessary to use molecular techniques to characterize microbial genetic resources. However, these studies are done using extracted environmental DNA, therefore we can find different results depending on the methodology chosen for the DNA extraction. Thus, this study aimed to improve a technique for extracting DNA from seawater and to demonstrate the importance of the DNA extraction methods in the study of microorganisms by cultivation-independent methods, it was characterized, by DGGE technique, the diversity of a marine bacterial community using different methods of DNA extraction. The improved methodology of DNA extraction from seawater resulted in a protocol similar in DNA quality, with better yield and approximately four times faster than the protocol initially described. Regarding the characterization by different DNA extraction protocols, we found distinct marine microbial community profiles, in relation the absence and presence of DNA bands and their relative intensity.

O objetivo do trabalho foi avaliar a qualidade, a quantidade e a capacidade de amplificação por PCR de DNA extraído de grãos de soja e milho, seus derivados e produtos acabados contendo como ingredientes obtidos desses grãos, com vistas à detecção de resíduos de organismos geneticamente modificados em alimentos. Para a amplificação de DNA pela PCR convencional, não houve melhor adequação de um protocolo de extração. Ambos métodos, CTAB e coluna de sílica tiveram desempenho comparável para as 32 matrizes avaliadas. A técnica de PCR em tempo real se mostrou mais sensível à qualidade do DNA testado e nesse contexto, o método CTAB se mostrou mais eficiente do que o método de coluna de sílica. Independentemente do método de extração utilizado não foi possível detectar DNA em óleos de soja e milho e em alguns derivados de amido, sugerindo que a aplicabilidade da lei de rotulagem pode esbarrar num entrave técnico no caso de algumas matrizes alimentares altamente processadas. / The aim of the study was to evaluate the quality, the quantity and the amplifiability by PCR of DNA isolated from soybean and maize grains and their by-products targeting the detection of genetically modified organisms in food. PCR amplification of DNA samples isolated either from CTAB and silica-column extraction methods achieved comparable performances. Both extraction methods showed similar results for the 32 tested matrices. The DNA amplification by real time PCR appeared to be affected by the quality of the isolated DNA. In this context, the CTAB extraction method showed to be more suitable when compared to the silica-column method. No DNA was amplified from soy and maize oils, as well as from some starch by-products, regardless the DNA extraction method used. It suggests that, the labeling requirement may rely on technical issues considering some high processed foodstuffs.

A tuberculose bovina, cujo agente etiológico é o Mycobacterium bovis, é uma zoonose de caráter crônico que representa uma das principais enfermidades em rebanhos bovinos. Devido às perdas consideráveis de bacilos viáveis nos processos de descontaminação, e também pelo consumo de várias semanas entre o isolamento primário e a identificação final da espécie, métodos moleculares funcionam como metodologia diagnóstica auxiliar à bacteriologia clássica. Estes métodos têm ampla aplicação no diagnóstico e tipificação da tuberculose bovina, no entanto, a baixa sensibilidade quando aplicados diretamente sobre homogeneizados de tecidos tem limitado sua difusão como método diagnóstico de rotina. A solução do problema, ao que tudo indica, passa por métodos de extração mais eficientes e menos vulneráveis aos fatores inibidores da amplificação. Assim, foram selecionadas 60 lesões granulomatosas de 60 bovinos condenados em abatedouro, 30 positivas ao isolamento de Mycobacterium bovis (padrão ouro positivo) e 30 negativas (padrão ouro negativo). Dessas lesões foram obtidos homogeneizados que foram submetidos a diferentes protocolos de extração de DNA, que por sua vez foram todos submetidos ao mesmo protocolo de amplificação. Os resultados mostraram que o protocolo de BOOM et al. (1990) modificado apresentou sensibilidade superior ao isolamento de M. bovis pelo método clássico. / The bovine tuberculosis, whose etiological agent is the Mycobacterium bovis, is a major zoonosis of cattle, of chronical course. Due to the expressive loss of viable bacilli during the decontamination processes and the long period between the primary isolation and the final identification of the specie, molecular methods are being used as auxiliary diagnostic methods to the classical bacteriology. These methods have a broad scope of application in the diagnosis and typification of bovine tuberculosis. However, the low sensibility when applied directly to tissue homogenates have limited its application as routine diagnostic method. The answer to this problem, as it seems, is the development of extraction methods that are more efficient and less vulnerable to inhibition factors of amplification. Therefore, 60 granulomatous lesions of 60 condemned bovines at abattoir were selected, 30 Mycobacterium bovis isolation positives (positive gold standard), and 30 negatives (negative gold standard). The homogenates were obtained from these lesions and were subjected to different DNA extraction protocols, all of which were submitted to the same amplification protocol. The results showed that BOOM et al. (1990) modified protocol showed superior sensibility than the M. bovis isolation through the classical method.

The alpaca is a small South American camelid (SAC) that is an important production animal in Peru, especially among the highly impoverished communities of the high Andes, and raised for its fiber and meat. Alpacas are highly reliant on the microbes within their digestive tracts to digest the plant material they consume; volatile fatty acids (VFAs) are released as a byproduct of this microbial fermentation and used as a major source of energy by the alpaca. To explore optimal parameters for alpaca microbiome analysis, performed 16S rRNA gene surveys on alpaca C1 and fecal samples that had been extracted using one of three different DNA extraction methods (PowerFecal® DNA Isolation Kit (MO BIO); ZR Fecal DNA MiniPrep™ (Zymo); and a non-commercial extraction method called salting out) and amplified using one of two different polymerase enzyme mixes (AccuPrime™ Pfx SuperMix and 5 PRIME HotMasterMix). We found that choice of polymerase enzyme had a profound effect on the recovered microbiome, with the majority of 5 PRIME-amplified fecal samples failing to amplify. Extraction method had an effect on the recovered microbiome of fecal samples (but not C1 samples), with samples extracted using the MO BIO kit and the salting out method recovering different communities. The Zymo extraction kit returned microbial communities comparable to each of the other extraction methods. These results suggested that the AccuPrime enzyme and either the MO BIO or Zymo kits were optimal for alpaca gut microbiome analysis. We also performed two 16S rRNA gene surveys, the first from alpacas fed either a grass hay (GH) or alfalfa hay (AH) diet, and the second a C1 survey of alpacas fed two-week periods of mixed grass hay plus one of four supplements. We discovered body site and diet effects on the microbiota of alpacas fed either the GH or AH diet, with samples grouping by general body site (C1, small intestine, and distal intestine) and diet. However, we found no significant effect on the C1 microbiome of alpacas administered grain supplements. To study how energy extraction related to the microbiome, we correlated OTUs from GH/AH-fed alpaca with C1 VFA abundances. We discovered no significant correlations, and a 16S survey of low body condition (LBC) and good body condition (GBC) alpacas showed no difference in C1 microbial communities. We concluded that the microbiota of the alpaca digestive tract follow trends seen in microbiome studies of ruminants, but found no evidence of a relationship between body condition, energy extraction, and the C1 microbiome in alpacas.

eDNA is a fast and popular method to collect information about species presence in the environment. eDNA is DNA that is collected from environmental samples, such as water, from DNA that is expelled from organisms interacting with their environment. eDNA is an effective way to find species with small populations and alien species. There are two ways to analyze eDNA, with high-throughput DNA sequencing methods and DNA metabarcoding or use of species-specific primers and PCR. In this study, we focus on the latter, designing species-specific primers for Burbot, Brown trout, and Atlantic Salmon, testing their validity in detecting eDNA of these species with functional PCR. We also evaluated eDNA collection methods, testing different scenarios in aquarium tanks with different number of dead and alive fishes. Primers and experimental setup such as use of different temperatures of the PCR reaction used in this study didn’t result in a functional PCR as determined by electrophoresis gel. There are some problems with the design of the PCR methods for eDNA since the purpose is to design methods that can identify certain species. However, future development of eDNA methods will probably include sequencing and not detection of PCR product sizes. eDNA methods will complete traditional trapping methods like net and electrofishing, but not replace them. / eDNA är en snabb och populär metod för att samla information om arters abundans i miljön. eDNA är DNA taget från miljö prover, så som vatten, från DNA som frigörs från organismer som intrigerar med deras miljön. eDNA är ett effektivt sätt att hitta arter med små populationer och främmande arter. De finns två olika sätt att analysera eDNA, med DNA-sekvenseringsmetoder med hög genomströmning och DNA-metabarkodning eller användning av artspecifika primrar och PCR. I denna studie fokuserade vi på den senare, designade artspecifika primers för lake, lax och öring, testa deras validitet vid detektering av eDNA hos dessa arter med funktionell PCR. Vi utvärderade också eDNA-insamlingsmetoder, testa olika scenarier i akvarietankar med olika antal döda och levande fiskar. Primers och experimentell uppställning, såsom användning av olika temperaturer för PCR-reaktionen som användes i denna studie, resulterade inte i en funktionell PCR såsom bestämd av elektroforesgel. Det finns några problem med utformningen av PCR-metoderna för eDNA, eftersom syftet är att utforma metoder som kan identifiera vissa arter. Emellertid kommer framtida utveckling av eDNA-metoder troligtvis att inkludera sekvensering och inte detektering av PCR-produktstorlekar. eDNA-metoder kommer att komplettera traditionella fångstmetoder som nät- och elektrofiske, men inte ersätta dem.

A tuberculose bovina, cujo agente etiológico é o Mycobacterium bovis, é uma zoonose de caráter crônico que representa uma das principais enfermidades em rebanhos bovinos. Devido às perdas consideráveis de bacilos viáveis nos processos de descontaminação, e também pelo consumo de várias semanas entre o isolamento primário e a identificação final da espécie, métodos moleculares funcionam como metodologia diagnóstica auxiliar à bacteriologia clássica. Estes métodos têm ampla aplicação no diagnóstico e tipificação da tuberculose bovina, no entanto, a baixa sensibilidade quando aplicados diretamente sobre homogeneizados de tecidos tem limitado sua difusão como método diagnóstico de rotina. A solução do problema, ao que tudo indica, passa por métodos de extração mais eficientes e menos vulneráveis aos fatores inibidores da amplificação. Assim, foram selecionadas 60 lesões granulomatosas de 60 bovinos condenados em abatedouro, 30 positivas ao isolamento de Mycobacterium bovis (padrão ouro positivo) e 30 negativas (padrão ouro negativo). Dessas lesões foram obtidos homogeneizados que foram submetidos a diferentes protocolos de extração de DNA, que por sua vez foram todos submetidos ao mesmo protocolo de amplificação. Os resultados mostraram que o protocolo de BOOM et al. (1990) modificado apresentou sensibilidade superior ao isolamento de M. bovis pelo método clássico. / The bovine tuberculosis, whose etiological agent is the Mycobacterium bovis, is a major zoonosis of cattle, of chronical course. Due to the expressive loss of viable bacilli during the decontamination processes and the long period between the primary isolation and the final identification of the specie, molecular methods are being used as auxiliary diagnostic methods to the classical bacteriology. These methods have a broad scope of application in the diagnosis and typification of bovine tuberculosis. However, the low sensibility when applied directly to tissue homogenates have limited its application as routine diagnostic method. The answer to this problem, as it seems, is the development of extraction methods that are more efficient and less vulnerable to inhibition factors of amplification. Therefore, 60 granulomatous lesions of 60 condemned bovines at abattoir were selected, 30 Mycobacterium bovis isolation positives (positive gold standard), and 30 negatives (negative gold standard). The homogenates were obtained from these lesions and were subjected to different DNA extraction protocols, all of which were submitted to the same amplification protocol. The results showed that BOOM et al. (1990) modified protocol showed superior sensibility than the M. bovis isolation through the classical method.

Made available in DSpace on 2014-07-29T16:24:18Z (GMT). No. of bitstreams: 1 Dissertacao Vanessa D Dias.pdf: 1360523 bytes, checksum: 2c315f161f69d4ede2c7375a35216403 (MD5) Previous issue date: 2012-03-02 / The sugarcane production areas are increasing in Brazil due to increased ethanol consumption by flex fuel cars. The planted area is growing, but productivity has been declining in recent years, and factors such as incidence of diseases in the crop may be contributing to this situation. Among the diseases, bacteria such as scald of the leaves and ratoon stunting disease, are of great importance to the crop because they can reduce productivity by up to 30% and the symptoms are not always displayed in the field, thus requiring advanced techniques to detect such bacterial diseases. Among the most used techniques for diagnosis serological tests are quite common, which has as main advantage the capacity of quantitative detection of the presence of bacteria in the culms. However, this detection is only possible if the bacterial title is relatively high. The PCR technique method is more sensitive for detecting low levels of bacteria in stems, but the DNA extractions should be performed in order to purify the DNA to reduce the presence of inhibitory substances in the extract. Thus in this study five different methods of DNA extraction of Xanthomonas albilineans and Leifsonia xyli subsp. xyli were tested and performed in three steps: pure bacteria, bacteria inoculated directly in the extract from five different varieties of sugarcane, and extract from a stem knowingly infected with these bacteria. The results indicate that the amplifications occur more frequently when the products and repeatability of the extractions are diluted by 10-4 in the Leaf Scald. Without this diluition steps, the amplification does not occur, even with the method of DNA extraction considered as a standard. Thus, it is concluded that the detection does not happen if the DNA extraction product is not diluted at least 1000 times, which should prevent the action of inhibitory factors that can hinder the PCR reactions. As for the ratoon stunting disease additional studies are needed to enable its detection by PCR. / O cultivo de cana-de-açúcar está em expansão no Brasil, devido ao crescente consumo de etanol por carros bicombustíveis. A área plantada está em crescimento, mas a produtividade nos últimos anos vem decrescendo, e fatores como incidência de doenças podem estar contribuindo para tal situação. Dentre as doenças, as bacterianas, como o Raquitismo das Soqueiras e a Escaldadura das Folhas, possuem grande importância para a cultura, pois podem reduzir a produtividade em até 30% e nem sempre os sintomas são visualizados em campo, necessitando assim de técnicas avançadas de detecção. Dentre as técnicas para diagnose, a mais utilizada por laboratórios são os testes sorológicos, que tem como vantagem detectar quantitativamente a presença das bactérias nos colmos mas, no entanto, possui a desvantagem de detectar somente quando a população bacteriana está relativamente alta. A técnica de PCR é mais sensível, detectando níveis baixos da população dessa bactéria nos colmos, e as etapas de extrações de DNA devem purificar o DNA para a redução da presença de substâncias inibidoras presentes no extrato. Assim, neste trabalho foram testadas cinco diferentes metodologias de extração de DNA para Xanthomonas albilineans e Leifsonia xyli subsp. xyli realizadas em três fontes: bactérias puras, bactérias adicionadas diretamente no caldo de cinco diferentes variedades de cana-de-açúcar, e caldo de colmos infectados com as bacterioses. Os resultados demonstram que as amplificações acontecem com maior freqüência e repetibilidade quando os produtos das extrações são diluídos em uma proporção de 10-4 para Escaldadura das folhas. Sem diluições as amplificações não ocorrem, mesmo com o método de extração de DNA com elevado grau de pureza, tal como CTAB. Assim, conclui-se que a detecção não ocorre se o produto das extrações de DNA não for diluído ao menos 1000 vezes, provavelmente reduzindo-se desta forma, o nível de inibidores presentes, proporcionando resultados positivos na técnica de amplificação via PCR. Para Raquitismo das soqueiras não conseguimos detectar Leifonia xyli subsp. xyli através de métodos rápidos de extração de DNA.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Soybeans are one of the crops with the highest expression in Brazil, both in area planted as in sales volume. The culture has as main pests defoliating caterpillars. Among these, stands out Chrysodeixis includens, pest that went from of secondary status in the 90s to a major defoliating caterpillar soybeans. Studies on genetic variation among populations and genetic structure of this species have not yet been carried out, and can help to indicate management practices. Molecular markers are tools indicated to genetically characterize insect populations. In order to use molecular tools, first, it is necessary a method for DNA extraction in quantity and quality that enables the practice in the laboratory. The goals of the study were to compare three DNA extraction methods for soybean caterpillars to applicate in PCR techniques, and analyze the molecular variability and the genetic structure of populations of C. includens in soybeans. Caterpillars of C. includens and S. eridania were collected from different sites in center soybean regions of Brazil, in 2011/12. The confirmation of the species was based on morphological characteristics of caterpillars according to identification keys. Samples of C. includes and S. eridania coming from Goiás were used for DNA extraction comparison test. The methods used were based on cell lysis by Sarcosyl, CTAB and SDS. Each method was compared for quantity, quality, economy and performance in PCR. The best DNA extraction method was chosen for extraction of all the caterpillars samples for molecular characterization work. Thirty populations of C. includens from nine Brazilian states were subjected to analysis of molecular variability and genetic structure with ISSR markers. The observed DNA extraction method with the best performance in the variables o was the DNA extraction method by Sarcosyl. ISSR generated 247 loci in 262 specimens analyzed. The estimated genetic diversity (HE) in populations ranged between 0.072 and 0.120, while the average was 0.094. The analysis of molecular variance indicates that 94% of the variability between individuals was expressed in 6% of the population and among populations (FST = 0.056, p = 0.001). The high level of gene flow and low genetic structure are indicatives of genetic information exchange between different sampling locations. The analysis of the genetic structure suggests the presence of two major groups which are not correlated to their sampling locations in Brazil. These results may indicate the recent colonization of C. includens in Brazil or the pattern of migration of moths following the cropping system in Brazil. Furthermore, the presence of two groups of C. includens suggest that the studies of development of resistance need to be further assessed for them both. / A soja é uma das culturas de maior expressão no Brasil, tanto em área plantada como em volume comercializado, e tem como principais pragas desfolhadoras as lagartas. Dentre essas, se destaca Chrysodeixis includens, praga que passou de secundária na década de 90 para uma das principais lagartas desfolhadoras da soja. Estudos sobre variações genéticas entre populações e estruturação genética dessa espécie ainda não foram realizados, e podem auxiliar na indicação práticas de manejo. Marcadores moleculares são ferramentas indicadas para caracterizar geneticamente populações de insetos. Mas para utilizar ferramentas moleculares, primeiramente, se faz necessário a extração de DNA em quantidade e qualidade que possibilita a prática no laboratório. Dessa forma, os objetivos do trabalho foram comparar três métodos de extração de DNA para lagartas da soja visando a aplicação com técnicas que utilizem a PCR. E analisar a variabilidade molecular e a estruturação genética de populações de C. includens na cultura da soja. Espécimes de lagartas de C. includens e Spodoptera eridania foram coletados de diferentes sítios de coleta nas principais áreas produtoras de soja do Brasil, safra de 2011/12. A confirmação da espécie foi baseada em características morfológicas das lagartas de acordo com chaves de identificação. As amostras de C. includens e S. eridania procedentes de Goiás foram utilizadas para o teste de comparação de extração de DNA. Os métodos utilizados eram cada um baseados na lise celular por Sarcosyl, CTAB e SDS. Cada método foi comparado quanto à quantidade, qualidade, economia e desempenho na PCR. O melhor método de extração de DNA foi utilizado para a extração de todas as amostras de lagartas para o trabalho de caracterização molecular. Trinta populações de C. includens de nove estados brasileiros foram submetidas a análise da variabilidade molecular e estrutura genética com marcadores ISSR. O método de extração de DNA que apresentou melhor desempenho nas variáveis observadas foi o método de extração de DNA por Sarcosyl. Os marcadores ISSR geraram 247 locos em 262 espécimes analisados. A diversidade genética estimada (HE) nas populações variaram entre 0,072 e 0,120, enquanto a média foi 0,094. A análise da variância molecular indica que 94% da variabilidade foi expressa entre indivíduos dentro das populações e 6% entre populações (FST = 0,056, p = 0,001). O alto nível de fluxo gênico e baixa estrutura genética são indicativos de troca de informação genética entre as diferentes locais de amostra. A análise da estrutura genética sugere a presença de dois grupos maiores que não se correlacionam com seus locais de amostragem no Brasil. Esses resultados podem indicar a recente colonização de C. includens no Brasil ou o padrão de migração das mariposas seguindo o sistema de cultivo no Brasil. Além disso, a presença de dois grupos de C. includens sugere que estudos sobre o desenvolvimento de resistência precisa ser avaliado sob outros ângulos para ambos os grupos.

O objetivo do trabalho foi avaliar a qualidade, a quantidade e a capacidade de amplificação por PCR de DNA extraído de grãos de soja e milho, seus derivados e produtos acabados contendo como ingredientes obtidos desses grãos, com vistas à detecção de resíduos de organismos geneticamente modificados em alimentos. Para a amplificação de DNA pela PCR convencional, não houve melhor adequação de um protocolo de extração. Ambos métodos, CTAB e coluna de sílica tiveram desempenho comparável para as 32 matrizes avaliadas. A técnica de PCR em tempo real se mostrou mais sensível à qualidade do DNA testado e nesse contexto, o método CTAB se mostrou mais eficiente do que o método de coluna de sílica. Independentemente do método de extração utilizado não foi possível detectar DNA em óleos de soja e milho e em alguns derivados de amido, sugerindo que a aplicabilidade da lei de rotulagem pode esbarrar num entrave técnico no caso de algumas matrizes alimentares altamente processadas. / The aim of the study was to evaluate the quality, the quantity and the amplifiability by PCR of DNA isolated from soybean and maize grains and their by-products targeting the detection of genetically modified organisms in food. PCR amplification of DNA samples isolated either from CTAB and silica-column extraction methods achieved comparable performances. Both extraction methods showed similar results for the 32 tested matrices. The DNA amplification by real time PCR appeared to be affected by the quality of the isolated DNA. In this context, the CTAB extraction method showed to be more suitable when compared to the silica-column method. No DNA was amplified from soy and maize oils, as well as from some starch by-products, regardless the DNA extraction method used. It suggests that, the labeling requirement may rely on technical issues considering some high processed foodstuffs.