Filtered bright and unfiltered hazy lager beer samples were either treated with high hydrostatic pressure (200, 250, 300, 350 MPa for 3, 5 and 10 min at 10&deg / C and 20&deg / C) or conventional heat pasteurization (60&deg / C for 15 min). Treatments did not affect ethanol, extract, fermentation degree, density and pH in comparison with untreated beers. Both treatments produced microbiologically stable products. Bitterness, color, protein sensitivity and chill haze parameters were affected by both the HHP and heat treatment. A storage period of 56 days showed that HHP and heat pasteurization had similar results in terms of pH and color. However, HHP treated samples had lower bitterness and protein sensitivity and higher chill haze values than the heat pasteurized samples which indicates HHP treatment had a positive effect on bitterness and protein sensitivity at the end of the storage period. The microbiological stability of HHP treated beers was comparable with heat-treated beers, and the development of both lactic and acetic acid bacteria was inhibited for 56 days of storage. Unfiltered beer samples had 7. 48, 7.15 and 2.64 log10cfu/ml of total yeasts, total aerobic and lactic acid bacteria counts, respectively. No colony formation of lactic acid bacteria was observed when the samples were pressurized at pressures equal to or higher than 300 MPa at 10&deg / C and 20&deg / C for 5 and 10 min. Total aerobic and total yeasts counts demonstrated more than 6 and 7 log-cycle reduction when pressurized at 350 MPa at 10&deg / C and 20&deg / C for 10 min, respectively. Heat treatment gave similar results in terms of log reductions as HHP.

The effect of pressure on the log reduction of six strains of E. coli O157:H7 and five serovars of Salmonella enterica were investigated in tryptic soy broth, sterile distilled water and commercially sterile orange and apple juice. Samples were subjected to high hydrostatic pressure (HHP) at 300 and 550 MPa for 2 minutes at 6°C, and then held for 24 hours at 4°C following treatment. E. coli O157:H7 strain E009 was the most pressure resistant, having a decrease of only 0.77 log10 CFU/ml directly after pressurization in TSB. S. Agona was the most pressure resistant Salmonella serovar tested with a decrease of 3.79 log¬10 CFU/ml in TSB at 550 MPa. The two most pressure resistant cultures were then used in a subsequent study using HHP in conjunction with antimicrobials (dimethyl dicarbonate [DMDC] at 62.5 and 125 ppm, hydrogen peroxide at 150 and 300 ppm, cinnamic acid, potassium salt at 125 and 250 ppm, potassium sorbate [KS] at 500 and 1000 ppm and sodium benzoate [NaB] at 500 and 1000). For both E. coli O157:H7 and Salmonella, the most effective antimicrobial was DMDC having a 5.79 and 5.96 log10 CFU/ml decrease directly following pressurization, respectively. Other treatments that were significantly different from the samples treated with no antimicrobial were hydrogen peroxide, and NaB at 500 ppm for E. coli O157:H7 and a treatment of NaB at 1000 ppm for S. Agona. After 24 hours at 4°C, S. Agona samples with added antimicrobials had a close to or above 5-log10 CFU/ml reduction. DMDC should be further investigated as an antimicrobial agent that can work in conjunction with HHP. / Master of Science

In this study, potential of high hydrostatic pressure (HHP) and essential oils (EOs) as natural antimicrobials was evaluated to produce E. coli safe and quality beef product. First, the individual and combined effects of antimicrobial activity (minimum inhibitory concentration) of basil, black cumin, cilantro, cumin, fenugreek, ginger, oregano, black pepper, rosemary, thyme, turmeric oil emulsions on E. coli ATCC 25922 with and without HHP treatment were evaluated. Cumin, oregano and thyme EOs showed highest antimicrobial activity against E. coli ATCC 25922. The synergy of selected EOs against E. coli ATCC 25922 was determined using the checkerboard method to obtain fractional inhibitory concentration index. Although their combinations did not show synergy, they expressed synergy when combined with HHP (400 MPa, 10 min, 20 °C) and the best combination was cumin and oregano EOs with HHP. Effects of HHP and EO combinations on inactivation of E. coli ATCC 25922 in beef were investigated using response surface methodology (RSM). Statistical analysis showed the model was significant for predicting log reduction with high accuracy. The significant model terms were pressure and time. Compared to control, HHP/EO treated samples showed no-post growth when stored up to 120 days at 4°C. Presented results suggests that the combination of HHP and antimicrobials has not only improved the process parameters (lowered pressure, time, and EO concentration) but also prevented recovery of E. coli ATCC 25922 during storage. RSM was employed to analyze the synergistic effects of HHP and EOs on beef quality (color, texture and lipid oxidation). Color indices were significantly affected by pressure, time and their interactions. Above 400 MPa the discoloration was similar to cooked beef and EO addition did not help color improvement. However, EOs showed significant antioxidant activity on both treated and untreated samples during storage. In conclusion, there is a great potential of HHP and EO combinations to enhance pathogen inactivation while keeping the quality of beef. Moreover, presence of EOs can prolong the shelf life of pressure treated beef. Therefore, the combination of HHP and EO is very promising for meat industry. / Ph. D. / Meat is a natural source of protein, essential vitamins, which makes it a nutrient-rich source of a healthy diet as well as an ideal environment for food-borne pathogens and spoilage bacteria. It is therefore essential to preserve very perishable meat products in terms of microbial contamination. As an alternative to many preservation methods such as chilling, canning, curing, smoking, dehydrating and heat treatment, a non-thermal mild food preservation technology of high hydrostatic pressure processing (HHP) is proposed for inactivating the most common meat contaminant bacteria of <i>E. coli</i>. Essential oils (EOs) can provide a solution for pasteurization requirements and reducing quality losses associated with HHP treatment. In this study the synergistic effect of selected EOs (basil, black cumin, cilantro, cumin, fenugreek, ginger, oregano, black pepper, rosemary, thyme, turmeric oil emulsions) and HHP technology on inactivation of <i>E. coli</i> ATCC 25922 on contaminated meat cuts were investigated. Experimental design and statistical analysis were conducted using response surface methodology (RSM). Combination of HHP/EO treated samples showed no-post growth of <i>E. coli</i> ATCC 25922 when meat samples were stored up to 120 days at 4°C. Presented results are suggesting that HHP in combination with EOs has increased the log reduction of <i>E.coli</i> and as well, decreased the quality losses (color, lipid oxidation textural analysis) compared to control samples where HHP is applied alone. As a conclusion, this study shows that there is a great potential of HHP and EO combinations to enhance pathogen inactivation while keeping the quality of beef.

No presente trabalho estudamos a renaturação sob alta pressão hidrostática de uma forma mutante da proteína verde fluorescente (enhanced GFP, eGFP), a qual somente emite fluorescência característica quando enovelada na sua forma nativa. A abordagem do presente estudo foi focada no controle da bioatividade da proteína recombinante, a fluorescência, como alternativa à determinação de solubilidade da proteína, fator que não é um indicador ideal de enovelamento proteico adequado. A ação da alta pressão na solubilização dos corpos de inclusão (CI) de eGFP produzidos em bactérias E. coli recombinantes e no enovelamento da proteína foi estudada. A compressão dos CI de eGFP em 2,4 kbar durante 30 minutos promoveu a dissociação dos agregados. No entanto, a incubação nesta condição não favoreceu o enovelamento da eGFP. O processo de renaturação foi avaliado em diversas condições de descompressão após a dissociação em 2,4 kbar. Durante a descompressão gradual, o aumento da fluorescência foi obtido em pressões que variaram entre a pressão atmosférica e 1,38kbar. Os níveis mais elevados de fluorescência de eGFP foram obtidos por incubação durante várias horas a níveis de pressão entre 0,35 e 0,69 kbar. Esta condição de pressão se mostrou favorável à renaturação de eGFP e é possível que também possa ser utilizada para favorecer o enovelamento de outras proteínas monoméricas. Ainda utilizando a eGFP como modelo, verificamos que os CI desta proteína produzidos por bactérias cultivadas em menor temperatura (37ºC) possuem maior quantidade de proteína recombinante apresentando a fluorescência característica em 509 nm, ou seja, na sua forma nativa, do que os CI expressos em temperaturas mais elevadas (42ºC e 47ºC). A análise realizada por espectroscopia de infravermelho (FT-IR) também demonstrou que os CI produzidos em temperaturas mais brandas possuem maior grau de estruturas secundárias semelhantes às da proteína na sua forma nativa. Além disso, os CI produzidos a 37ºC também são mais facilmente solubilizados pela ação da alta pressão do que aqueles produzidos em maior temperatura. Conforme esperado, a renaturação da eGFP a partir de CI produzidos a 37ºC foi 25 vezes mais eficiente do que a obtida utilizando CI produzidos a 47ºC. No presente estudo demonstramos também que a dissociação dos agregados exercida pela ação da alta pressão (2,4 kbar) pode ser amplificada quando em associação com a incubação em baixa temperatura (-9ºC) e que a combinação destas duas propriedades físicas eleva a solubilização dos agregados em CI, com a consequente elevação dos rendimentos de renaturação de eGFP. Mostramos ainda no presente estudo que a cinética de renaturação de eGFP em 0,69 kbar é proporcional à temperatura de incubação (entre 10ºC e 50ºC). O nível mais elevado de fluorescência foi obtido quando a renaturação de eEGP foi realizada a 20ºC. A taxa de maturação do cromóforo da eGFP é mais fortemente afetada pela temperatura do que a taxa de enovelamento da proteína. Em conclusão, a temperatura de produção dos CI, a temperatura de dissociação dos agregados e a temperatura de enovelamento podem afetar muito o rendimento e a cinética da renaturação de eGFP em alta pressão. Os resultados do presente estudo podem abrir novas perspectivas para melhorias no processo de enovelamento de proteínas a partir de CI utilizando alta pressão. Também neste trabalho descrevemos a renaturação das proteínas de Xac, PilB e os produtos dos genes XAC2810 e XAC3272 nunca antes obtidas na forma solúvel. Os rendimentos de solubilização destas três proteínas foram muito altos, entre 75% e 89%. A proteína PilB renaturada em alta pressão apresentou atividade ATPasica elevada, o que nunca antes foi demonstrado para a PilB de Xac. / In the present work we studied the refolding under high hydrostatic pressure of a mutant form of the green fluorescent protein (eGFP), which only emits the green characteristic fluorescence when in the native folded state. The approach of the present study was focused on controlling the bioactivity of the recombinant protein, the fluorescence, as an alternative for the determination of protein solubility, which is not an ideal indicator of proper protein folding. We studied the action of high pressure in the solubilization of the inclusion bodies (IB) of eGFP produced in bacteria E. coli and in the folding of this protein. The compression of a suspension of eGFP IB at 2.4 kbar for 30 minutes promoted dissociation of aggregates. However, the eGFP folding, monitored by the fluorescence at 509 nm, does not occur in this pressure level. The process of eGFP refolding was evaluated under various decompression conditions after dissociation of the IB at 2.4 kbar. During the gradual decompression, the increase in fluorescence was achieved at pressures ranging between atmospheric pressure and 1.38 kbar. The higher levels of eGFP fluorescence were obtained by incubation for several hours at pressure levels between 0.35 and 0.69 kbar. It is possible that the pressure condition that proved favorable for refolding of eGFP can also be used to favor the folding of other monomeric proteins. Using eGFP as a model, we also found that the IB produced by bacteria grown in a relatively low temperature (37ºC) is more fluorescent, presenting a higher amount of recombinant protein with the characteristic fluorescence at 509 nm, i.e., in its native form, than the IB expressed at higher temperatures (42ºC and 47ºC). The analysis by infrared spectroscopy (FT-IR) also demonstrated that the IB produced at milder temperatures have a higher degree of secondary structure similar to the protein in its native form. Furthermore, the IB produced at 37ºC are also more readily solubilized by the action of high pressure than those produced at the higher temperatures. As expected, the folding of eGFP from IB produced at 37ºC was 25 times more efficient than that obtained using IB produced at 47ºC. In this study we demonstrated that the dissociation of aggregates exerted by the action of high pressure (2.4 kbar) can be amplified by combination with incubation at low temperature (-9ºC) and the association of these two physical properties can be used to increase the solubilization of the aggregates in IB, with a consequent increase in the yield of eGFP refolding. In the present study we also showed that the kinetics of refolding of eGFP is proportional to temperature (10ºC 50ºC). The higher level of fluorescence was obtained when the refolding of eGFP was performed at 20°C. The rate of maturation of the eGFP chromophore is more strongly affected by temperature than the rate of folding of the protein. In conclusion, the temperature of production of IB, the temperature of dissociation of aggregates and the folding temperature can greatly affect the yield and kinetics of refolding of eGFP at high pressure. The results of this study may open new perspectives for improvements in the process of protein folding from IB using high pressure. In this paper we also describe the refolding of the proteins of Xac, PilB and the gene products XAC2810 and XAC3272, which have never before been achieved in soluble form. The yields of solubilization/refolding of these three proteins were very high, between 75% and 89%. The protein PilB refolded at high pressure presented high ATPase activity, which has never been shown for the PilB of Xac.

A produção de proteínas recombinantes é uma ferramenta essencial para a indústria biotecnológica e suporta a expansão da pesquisa biológica moderna. Uma variedade de hospedeiros pode ser utilizada para produzir estas proteínas e dentre eles, as bactérias E. coli são as hospedeiras mais utilizadas. No entanto, a expressão heteróloga de genes em E. coli frequentemente resulta em um processo de enovelamento incompleto que leva ao acúmulo de agregados insolúveis, conhecidos como corpos de inclusão (CI). Altas pressões hidrostáticas são capazes de desfavorecer interações intermoleculares hidrofóbicas e eletrostáticas, levando à dissociação dos agregados e por isso são úteis para solubilizar e renaturar proteínas agregadas em CI. O presente trabalho teve como objetivo o estudo do processo de desagregação dos CI e de renaturação das proteínas oligoméricas subunidade B da toxina colérica (CTB) e região globular da fibra adenoviral (RGFA) utilizando altas pressões hidrostáticas. A toxina colérica (CT) é composta por uma subunidade A e cinco subunidades B combinadas em uma holotoxina AB5. A CTB é a porção pentamérica não tóxica da CT, responsável pela ligação da holotoxina ao receptor gangliosídeo GM1. A fibra do adenovírus é uma proteína homotrimérica que forma parte do capsídeo viral, organizada em três regiões: a cauda N-terminal, a haste central e a região C-terminal (região globular). A RGFA se liga à proteína de membrana CAR nas células hospedeiras e promove a internalização do vírus. Os estudos apresentados neste trabalho demonstraram que a alta pressão hidrostática foi eficaz na desagregação dos CI da CTB e da RGFA. As condições de renaturação foram otimizadas utilizando-se diferentes proporções do par redox glutationa oxidada e reduzida, concentrações de agentes caotrópicos, presença de aditivos e esquemas diferenciados de compressão/descompressão daqueles previamente descritos na literatura. CTB solúvel e pentamérica foi obtida pela compressão da suspensão de CI a 2,4 kbar por 16 horas em tampão TrisHCl 50 mM pH 8,5, 1 mM de tween 20 e descompressão direta seguida de incubação em pressão atmosférica. O rendimento de renaturação da CTB solúvel e pentamérica foi de até 45 % e 288 mg de CTB/litro de cultura bacteriana. Esta proteína apresentou estrutura regular e atividade biológica. RGFA trimérica foi obtida pela compressão da suspensão de CI em tampão TrisHCl 50 mM pH 8,0 e 0,5 M de L-arginina a 2,4 kbar por 1,5 horas e 0,4 kbar por 16 horas antes da completa descompressão. O rendimento de proteína solúvel trimérica da RGFA foi de 4 %, porém não foi possível obter a atividade biológica desta proteína. / The production of recombinant proteins is an essential tool for the biotechnology industry and supports the expansion of modern biological research. Recombinant proteins can be produced by a variety of hosts and among them the bacteria E. coli is the most commonly used. However, the expression of heterologous genes in E. coli often results in an incomplete folding process that leads to the accumulation of insoluble aggregates known as inclusion bodies (IB). The application of high hydrostatic pressure impairs intermolecular hydrophobic and electrostatic interactions of proteins in solution, leading to dissociation of aggregates and is therefore useful tool to solubilize and refold aggregated proteins in IB. This work aimed to study the process of disaggregation of IB and refolding of oligomeric proteins the B subunit of cholera toxin (CTB) and the globular region of the adenoviral fiber (RGFA) using high hydrostatic pressure. The cholera toxin (CT) comprises one A subunit and five B subunits, combined in the AB5 holotoxin. The pentameric CTB is non-toxic moiety of CT which is responsible for binding to the receptor ganglioside GM1 holotoxin. The adenovirus fiber is a homotrimeric protein wich forms part of the viral capsid and it is organized into three regions: the N-terminal tail, the central rod and the C-terminal region (globular region). The RGFA binds to membrane protein CAR in host cells and promotes the internalization of virus. The studies presented here demonstrate that high hydrostatic pressure was effective in the disaggregation of the CTB and RGFA IB. The refolding conditions were optimized using different proportions of the redox couple oxidated and reduced glutathione, concentrations of chaotropic agents, presence of additives and pressure/decompression schemes distinguished from the previously described in the literature. Soluble pentameric CTB was obtained when the suspension of IB were compressed at 2.4 kbar for 16 hours in 50 mM of Tris-HCl buffer pH 8.5, 1 mM of tween 20, followed by direct decompression and incubation at atmospheric pressure. The yield of refolded soluble pentameric CTB was up to 45 % and 288 mg of CTB/ liter of bacterial culture. This protein was shown to presented regular structure and biological activity. Trimeric RGFA was obtained by compression of the suspension of IB in 50 mM of Tris-HCl buffer pH 8.0, 0.5M L-arginine at 2.4 kbar for 1.5 hours and at 0.4 kbar for 16 hours prior to the complete decompression. The yield of soluble trimeric RGFA was 4 %, however this protein did not present biological activity.

A produção de proteínas recombinantes é uma ferramenta essencial para a indústria biotecnológica e suporta a expansão da pesquisa biológica moderna. Uma variedade de hospedeiros pode ser utilizada para produzir estas proteínas e dentre eles, as bactérias E. coli são as hospedeiras mais utilizadas. No entanto, a expressão heteróloga de genes em E. coli frequentemente resulta em um processo de enovelamento incompleto que leva ao acúmulo de agregados insolúveis, conhecidos como corpos de inclusão (CI). Altas pressões hidrostáticas são capazes de desfavorecer interações intermoleculares hidrofóbicas e eletrostáticas, levando à dissociação dos agregados e por isso são úteis para solubilizar e renaturar proteínas agregadas em CI. O presente trabalho teve como objetivo o estudo do processo de desagregação dos CI e de renaturação das proteínas oligoméricas subunidade B da toxina colérica (CTB) e região globular da fibra adenoviral (RGFA) utilizando altas pressões hidrostáticas. A toxina colérica (CT) é composta por uma subunidade A e cinco subunidades B combinadas em uma holotoxina AB5. A CTB é a porção pentamérica não tóxica da CT, responsável pela ligação da holotoxina ao receptor gangliosídeo GM1. A fibra do adenovírus é uma proteína homotrimérica que forma parte do capsídeo viral, organizada em três regiões: a cauda N-terminal, a haste central e a região C-terminal (região globular). A RGFA se liga à proteína de membrana CAR nas células hospedeiras e promove a internalização do vírus. Os estudos apresentados neste trabalho demonstraram que a alta pressão hidrostática foi eficaz na desagregação dos CI da CTB e da RGFA. As condições de renaturação foram otimizadas utilizando-se diferentes proporções do par redox glutationa oxidada e reduzida, concentrações de agentes caotrópicos, presença de aditivos e esquemas diferenciados de compressão/descompressão daqueles previamente descritos na literatura. CTB solúvel e pentamérica foi obtida pela compressão da suspensão de CI a 2,4 kbar por 16 horas em tampão TrisHCl 50 mM pH 8,5, 1 mM de tween 20 e descompressão direta seguida de incubação em pressão atmosférica. O rendimento de renaturação da CTB solúvel e pentamérica foi de até 45 % e 288 mg de CTB/litro de cultura bacteriana. Esta proteína apresentou estrutura regular e atividade biológica. RGFA trimérica foi obtida pela compressão da suspensão de CI em tampão TrisHCl 50 mM pH 8,0 e 0,5 M de L-arginina a 2,4 kbar por 1,5 horas e 0,4 kbar por 16 horas antes da completa descompressão. O rendimento de proteína solúvel trimérica da RGFA foi de 4 %, porém não foi possível obter a atividade biológica desta proteína. / The production of recombinant proteins is an essential tool for the biotechnology industry and supports the expansion of modern biological research. Recombinant proteins can be produced by a variety of hosts and among them the bacteria E. coli is the most commonly used. However, the expression of heterologous genes in E. coli often results in an incomplete folding process that leads to the accumulation of insoluble aggregates known as inclusion bodies (IB). The application of high hydrostatic pressure impairs intermolecular hydrophobic and electrostatic interactions of proteins in solution, leading to dissociation of aggregates and is therefore useful tool to solubilize and refold aggregated proteins in IB. This work aimed to study the process of disaggregation of IB and refolding of oligomeric proteins the B subunit of cholera toxin (CTB) and the globular region of the adenoviral fiber (RGFA) using high hydrostatic pressure. The cholera toxin (CT) comprises one A subunit and five B subunits, combined in the AB5 holotoxin. The pentameric CTB is non-toxic moiety of CT which is responsible for binding to the receptor ganglioside GM1 holotoxin. The adenovirus fiber is a homotrimeric protein wich forms part of the viral capsid and it is organized into three regions: the N-terminal tail, the central rod and the C-terminal region (globular region). The RGFA binds to membrane protein CAR in host cells and promotes the internalization of virus. The studies presented here demonstrate that high hydrostatic pressure was effective in the disaggregation of the CTB and RGFA IB. The refolding conditions were optimized using different proportions of the redox couple oxidated and reduced glutathione, concentrations of chaotropic agents, presence of additives and pressure/decompression schemes distinguished from the previously described in the literature. Soluble pentameric CTB was obtained when the suspension of IB were compressed at 2.4 kbar for 16 hours in 50 mM of Tris-HCl buffer pH 8.5, 1 mM of tween 20, followed by direct decompression and incubation at atmospheric pressure. The yield of refolded soluble pentameric CTB was up to 45 % and 288 mg of CTB/ liter of bacterial culture. This protein was shown to presented regular structure and biological activity. Trimeric RGFA was obtained by compression of the suspension of IB in 50 mM of Tris-HCl buffer pH 8.0, 0.5M L-arginine at 2.4 kbar for 1.5 hours and at 0.4 kbar for 16 hours prior to the complete decompression. The yield of soluble trimeric RGFA was 4 %, however this protein did not present biological activity.

No presente trabalho estudamos a renaturação sob alta pressão hidrostática de uma forma mutante da proteína verde fluorescente (enhanced GFP, eGFP), a qual somente emite fluorescência característica quando enovelada na sua forma nativa. A abordagem do presente estudo foi focada no controle da bioatividade da proteína recombinante, a fluorescência, como alternativa à determinação de solubilidade da proteína, fator que não é um indicador ideal de enovelamento proteico adequado. A ação da alta pressão na solubilização dos corpos de inclusão (CI) de eGFP produzidos em bactérias E. coli recombinantes e no enovelamento da proteína foi estudada. A compressão dos CI de eGFP em 2,4 kbar durante 30 minutos promoveu a dissociação dos agregados. No entanto, a incubação nesta condição não favoreceu o enovelamento da eGFP. O processo de renaturação foi avaliado em diversas condições de descompressão após a dissociação em 2,4 kbar. Durante a descompressão gradual, o aumento da fluorescência foi obtido em pressões que variaram entre a pressão atmosférica e 1,38kbar. Os níveis mais elevados de fluorescência de eGFP foram obtidos por incubação durante várias horas a níveis de pressão entre 0,35 e 0,69 kbar. Esta condição de pressão se mostrou favorável à renaturação de eGFP e é possível que também possa ser utilizada para favorecer o enovelamento de outras proteínas monoméricas. Ainda utilizando a eGFP como modelo, verificamos que os CI desta proteína produzidos por bactérias cultivadas em menor temperatura (37ºC) possuem maior quantidade de proteína recombinante apresentando a fluorescência característica em 509 nm, ou seja, na sua forma nativa, do que os CI expressos em temperaturas mais elevadas (42ºC e 47ºC). A análise realizada por espectroscopia de infravermelho (FT-IR) também demonstrou que os CI produzidos em temperaturas mais brandas possuem maior grau de estruturas secundárias semelhantes às da proteína na sua forma nativa. Além disso, os CI produzidos a 37ºC também são mais facilmente solubilizados pela ação da alta pressão do que aqueles produzidos em maior temperatura. Conforme esperado, a renaturação da eGFP a partir de CI produzidos a 37ºC foi 25 vezes mais eficiente do que a obtida utilizando CI produzidos a 47ºC. No presente estudo demonstramos também que a dissociação dos agregados exercida pela ação da alta pressão (2,4 kbar) pode ser amplificada quando em associação com a incubação em baixa temperatura (-9ºC) e que a combinação destas duas propriedades físicas eleva a solubilização dos agregados em CI, com a consequente elevação dos rendimentos de renaturação de eGFP. Mostramos ainda no presente estudo que a cinética de renaturação de eGFP em 0,69 kbar é proporcional à temperatura de incubação (entre 10ºC e 50ºC). O nível mais elevado de fluorescência foi obtido quando a renaturação de eEGP foi realizada a 20ºC. A taxa de maturação do cromóforo da eGFP é mais fortemente afetada pela temperatura do que a taxa de enovelamento da proteína. Em conclusão, a temperatura de produção dos CI, a temperatura de dissociação dos agregados e a temperatura de enovelamento podem afetar muito o rendimento e a cinética da renaturação de eGFP em alta pressão. Os resultados do presente estudo podem abrir novas perspectivas para melhorias no processo de enovelamento de proteínas a partir de CI utilizando alta pressão. Também neste trabalho descrevemos a renaturação das proteínas de Xac, PilB e os produtos dos genes XAC2810 e XAC3272 nunca antes obtidas na forma solúvel. Os rendimentos de solubilização destas três proteínas foram muito altos, entre 75% e 89%. A proteína PilB renaturada em alta pressão apresentou atividade ATPasica elevada, o que nunca antes foi demonstrado para a PilB de Xac. / In the present work we studied the refolding under high hydrostatic pressure of a mutant form of the green fluorescent protein (eGFP), which only emits the green characteristic fluorescence when in the native folded state. The approach of the present study was focused on controlling the bioactivity of the recombinant protein, the fluorescence, as an alternative for the determination of protein solubility, which is not an ideal indicator of proper protein folding. We studied the action of high pressure in the solubilization of the inclusion bodies (IB) of eGFP produced in bacteria E. coli and in the folding of this protein. The compression of a suspension of eGFP IB at 2.4 kbar for 30 minutes promoted dissociation of aggregates. However, the eGFP folding, monitored by the fluorescence at 509 nm, does not occur in this pressure level. The process of eGFP refolding was evaluated under various decompression conditions after dissociation of the IB at 2.4 kbar. During the gradual decompression, the increase in fluorescence was achieved at pressures ranging between atmospheric pressure and 1.38 kbar. The higher levels of eGFP fluorescence were obtained by incubation for several hours at pressure levels between 0.35 and 0.69 kbar. It is possible that the pressure condition that proved favorable for refolding of eGFP can also be used to favor the folding of other monomeric proteins. Using eGFP as a model, we also found that the IB produced by bacteria grown in a relatively low temperature (37ºC) is more fluorescent, presenting a higher amount of recombinant protein with the characteristic fluorescence at 509 nm, i.e., in its native form, than the IB expressed at higher temperatures (42ºC and 47ºC). The analysis by infrared spectroscopy (FT-IR) also demonstrated that the IB produced at milder temperatures have a higher degree of secondary structure similar to the protein in its native form. Furthermore, the IB produced at 37ºC are also more readily solubilized by the action of high pressure than those produced at the higher temperatures. As expected, the folding of eGFP from IB produced at 37ºC was 25 times more efficient than that obtained using IB produced at 47ºC. In this study we demonstrated that the dissociation of aggregates exerted by the action of high pressure (2.4 kbar) can be amplified by combination with incubation at low temperature (-9ºC) and the association of these two physical properties can be used to increase the solubilization of the aggregates in IB, with a consequent increase in the yield of eGFP refolding. In the present study we also showed that the kinetics of refolding of eGFP is proportional to temperature (10ºC 50ºC). The higher level of fluorescence was obtained when the refolding of eGFP was performed at 20°C. The rate of maturation of the eGFP chromophore is more strongly affected by temperature than the rate of folding of the protein. In conclusion, the temperature of production of IB, the temperature of dissociation of aggregates and the folding temperature can greatly affect the yield and kinetics of refolding of eGFP at high pressure. The results of this study may open new perspectives for improvements in the process of protein folding from IB using high pressure. In this paper we also describe the refolding of the proteins of Xac, PilB and the gene products XAC2810 and XAC3272, which have never before been achieved in soluble form. The yields of solubilization/refolding of these three proteins were very high, between 75% and 89%. The protein PilB refolded at high pressure presented high ATPase activity, which has never been shown for the PilB of Xac.

The aim of this study was to investigate the effect of high hydrostatic pressure (HHP) treatment (200, 300, 400 MPa / 5

Shrimp and mussel samples were cleaned, washed and exposed to steam before freezing. HHP treatment was performed at combinations of 200, 220 and 250 MPa at 25, 30, 40 and 50&deg / C for 10 and 20 minutes. Microbial analysis were performed by analyzing the effect of treatments on the microbial reduction in the samples. Based on the results of the microbial reduction, the best combinations of HHP treatments were determined as 250 MPa, 50&deg / C, 10 minute for shrimps and 220 MPa, 50&deg / C, 10 minute for mussels where total microbial inactivation was achieved. Storage analysis was performed on the samples, treated at the selected HHP combinations and stored at room (25&deg / C) and refrigeration temperatures (4&deg / C). For the storage analysis, variations in Total Volatile Bases (TVB-N) and pH were measured. According to the results evaluated, shelf-life of the shrimps were detected as 10 and 16 days for storage at room and refrigeration temperature, respectively as compared to 4 days of untreated sample at 4oC. Similarly shelf-life for the mussel samples were obtained as 12 days for storage at room and 18 day for storage at refrigeration temperature as compared to 4 days of untreated sample at 4oC. HHP-at the studied parameters for shrimps and mussels- can be offered as an alternative method for the preservation of shell-fish instead of conventional frozen food technology, which is currently used in the industry, since it gives the opportunity to handle the samples at lower temperatures for the post-production period resulting in both reduction of energy required and operational costs without sacrificing from the quality as measured by microbial reduction, TVB-N and pH.

Drying is a process of moisture removal due to simultaneous heat and mass transfer. High hydrostatic pressure (HHP) processing subjects liquid and solid foods, with or without packaging, to pressures between 100 and 800 MPa. The application of HHP affects cell wall structures, leaving the cells more permeable, facilitating the diffusion and providing higher drying rates. In this study, two variety of apples, i.e. Amasya and red delicious, green beans and carrots were pretreated with HHP at different pressure-time-temperature combinations (100 &ndash / 300 MPa for 5 &ndash / 45 min at 20 and 35&deg / C) prior to drying. Hot air drying experiments were carried at different temperatures (27, 45, 65, and 85&deg / C) and air velocity of 0.4 and 0.8 m/s. To obtain the drying data, samples were subjected to hot air drying under constant external conditions. The applicability of 14 kinetic models selected from the literature for the drying of fruits and vegetables was determined by appropriate statistical analyses procedures. Improving the drying conditions by increasing the drying temperature generally masked the effect of HHP pretreatment on drying rate. Only for green beans, HHP treatments at 20&deg / C decreased the drying rate. Generally pressures of HHP pretreatment higher than 100 MPa caused cell permeabilization resulted in higher drying rates for apples and carrots. Among the 14 models, modified Page model for apples, and modified Page and two term exponential models for green beans and carrots were found to best explain the drying behaviors.