João A. Queiroz

Bio: João A. Queiroz is an academic researcher from University of Beira Interior. The author has contributed to research in topics: Hydrophilic interaction chromatography & Affinity chromatography. The author has an hindex of 44, co-authored 305 publications receiving 8035 citations.

Coriander (Coriandrum sativum L.) essential oil: its antibacterial activity and mode of action evaluated by flow cytometry.

Abstract: The aim of this work was to study the antibacterial effect of coriander (Coriandrum sativum) essential oil against Gram-positive and Gram-negative bacteria. Antibacterial susceptibility was evaluated using classical microbiological techniques concomitantly with the use of flow cytometry for the evaluation of cellular physiology. Our results showed that coriander oil has an effective antimicrobial activity against all bacteria tested. Also, coriander oil exhibited bactericidal activity against almost all bacteria tested, with the exception of Bacillus cereus and Enterococcus faecalis. Propidium iodide incorporation and concomitant loss of all other cellular functions such as efflux activity, respiratory activity and membrane potential seem to suggest that the primary mechanism of action of coriander oil is membrane damage, which leads to cell death. The results obtained herein further encourage the use of coriander oil in antibacterial formulations due to the fact that coriander oil effectively kills pathogenic bacteria related to foodborne diseases and hospital infections.

Purification of a cystic fibrosis plasmid vector for gene therapy using hydrophobic interaction chromatography.

Abstract: The success and validity of gene therapy and DNA vaccination in in vivo experiments and human clinical trials depend on the ability to produce large amounts of plasmid DNA according to defined specifications. A new method is described for the purification of a cystic fibrosis plasmid vector (pCF1-CFTR) of clinical grade, which includes an ammonium sulfate precipitation followed by hydrophobic interaction chromatography (HIC) using a Sepharose gel derivatized with 1,4-butanediol-diglycidylether. The use of HIC took advantage of the more hydrophobic character of single-stranded nucleic acid impurities as compared with double-stranded plasmid DNA. RNA, denatured genomic and plasmid DNAs, with large stretches of single strands, and lipopolysaccharides (LPS) that are more hydrophobic than supercoiled plasmid, were retained and separated from nonbinding plasmid DNA in a 14-cm HIC column. Anion-exchange HPLC analysis proved that >70% of the loaded plasmid was recovered after HIC. RNA and denatured plasmid in the final plasmid preparation were undetectable by agarose electrophoresis. Other impurities, such as host genomic DNA and LPS, were reduced to residual values with the HIC column (<6 ng/microg pDNA and 0.048 EU/microg pDNA, respectively). The total reduction in LPS load in the combined ammonium acetate precipitation and HIC was 400,000-fold. Host proteins were not detected in the final preparation by bicinchoninic acid (BCA) assay and sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with silver staining. Plasmid identity was confirmed by restriction analysis and biological activity by transformation experiments. The process presented constitutes an advance over existing methodologies, is scaleable, and meets quality standards because it does not require the use of additives that usually pose a challenge to validation and raise regulatory concerns.

Bacterial lipases: an overview of production, purification and biochemical properties.

Abstract: Lipases, triacylglycerol hydrolases, are an important group of biotechnologically relevant enzymes and they find immense applications in food, dairy, detergent and pharmaceutical industries. Lipases are by and large produced from microbes and specifically bacterial lipases play a vital role in commercial ventures. Some important lipase-producing bacterial genera include Bacillus, Pseudomonas and Burkholderia. Lipases are generally produced on lipidic carbon, such as oils, fatty acids, glycerol or tweens in the presence of an organic nitrogen source. Bacterial lipases are mostly extracellular and are produced by submerged fermentation. The enzyme is most commonly purified by hydrophobic interaction chromatography, in addition to some modern approaches such as reverse micellar and aqueous two-phase systems. Most lipases can act in a wide range of pH and temperature, though alkaline bacterial lipases are more common. Lipases are serine hydrolases and have high stability in organic solvents. Besides these, some lipases exhibit chemo-, regio- and enantioselectivity. The latest trend in lipase research is the development of novel and improved lipases through molecular approaches such as directed evolution and exploring natural communities by the metagenomic approach.

Global Epidemiology of Campylobacter Infection

Abstract: Campylobacter jejuni infection is one of the most widespread infectious diseases of the last century. The incidence and prevalence of campylobacteriosis have increased in both developed and developing countries over the last 10 years. The dramatic increase in North America, Europe, and Australia is alarming, and data from parts of Africa, Asia, and the Middle East indicate that campylobacteriosis is endemic in these areas, especially in children. In addition to C. jejuni, there is increasing recognition of the clinical importance of emerging Campylobacter species, including Campylobacter concisus and Campylobacter ureolyticus. Poultry is a major reservoir and source of transmission of campylobacteriosis to humans. Other risk factors include consumption of animal products and water, contact with animals, and international travel. Strategic implementation of multifaceted biocontrol measures to reduce the transmission of this group of pathogens is paramount for public health. Overall, campylobacteriosis is still one of the most important infectious diseases that is likely to challenge global health in the years to come. This review provides a comprehensive overview of the global epidemiology, transmission, and clinical relevance of Campylobacter infection.

Lignocellulosic agriculture wastes as biomass feedstocks for second-generation bioethanol production: concepts and recent developments

Abstract: Production of liquid biofuels, such as bioethanol, has been advocated as a sustainable option to tackle the problems associated with rising crude oil prices, global warming and diminishing petroleum reserves. Second-generation bioethanol is produced from lignocellulosic feedstock by its saccharification, followed by microbial fermentation and product recovery. Agricultural residues generated as wastes during or after processing of agricultural crops are one of such renewable and lignocellulose-rich biomass resources available in huge amounts for bioethanol production. These agricultural residues are converted to bioethanol in several steps which are described here. This review enlightens various steps involved in production of the second-generation bioethanol. Mechanisms and recent advances in pretreatment, cellulases production and second-generation ethanol production processes are described here.