Abstract The aim of this study was to evaluate the capacity of two strains of lactic acid bacteria (LAB), Lactobacillus rhamnosus and Lactococcus lactis, and a yeast strain, Saccharomyces cerevisiae, inactivated by heat (121 °C, 10 min), from binding to aflatoxin M1 (AFM1), as well as the interaction between these microorganisms, aflatoxin M1 and the Minas Frescal cheese matrix after 2 and 30 days of storage. The ability of LABs and S. cerevisiae to bind AFM1 to Minas Frescal cheese was evaluated by high performance liquid chromatography (HPLC) composed of a fluorescence detector. The interaction between these microorganisms and AFM1 was evaluated using a scanning electron microscope composed of a backscattered electron detector with a voltage of 15 kV and magnifications of 1000 ×, 5000 × and 8000 ×. The use of microorganisms as a biological method is efficient in reducing AFM1 in Minas Frescal cheese and does not affect the microbiological parameters. AFM1 reduction varied according to the microorganism used in the treatments. S cerevisiae showed greater capacity to bind AFM1 over time, compared to LABs. Scanning electron microscopy was especially useful, confirming that lactic acid bacteria and S. cerevisae were able to bind AFM1 particles in Minas Frescal cheese.
Abstract Dairy cattle when fed on aflatoxin B1 may excrete aflatoxin M1 in milk as a consequence of dietary exposure. Once AFM1 is excreted in milk, it is present in dairy products such as cheese, yogurt, among others. This mycotoxin is quite resistant to temperature therefore heat treatments like pasteurization and ultra-pasteurization are not enough to inactivate it. In this context, this article provides an overview of the biological decontamination methods on milk and cheese of the last decade, as a contribution to evaluate the evolution of this strategy as well as its efficiency according to their authors. Relevant studies published between January 2009 and May 2019 were selected after a systematic search of the literature in PubMed, Science direct and Google Scholar databases. According with our research in the last decade few studies have been published on these methods and unfortunately none of the published studies tested such methods in cheese. Throughout the research many studies on decontamination methods were found, however, in phosphate buffered saline solution or in culture medium. Further studies on biological decontamination on milk and mainly on cheese are necessary for this technique to be better developed and applied to a large scale in the industries.
Abstract Silver nanoparticles (AgNPs) are antimicrobial agents that have a wide spectrum of action, including against pathogenic bacteria and spoilage fungi. However, their mechanism of action is not completely clarified. Nowadays, scientific interest on biological synthesis of AgNPs is growing, with emphasis in their extracellular biosynthesis by microbial cells, as it is the most reliable and ecologically correct method for production, yielding no toxic residues. AgNPs may be incorporated to biodegradable and non-biodegradable polymers for the production of food packages with antimicrobial properties, leading to greater safety and longer shelf life. However, it is important to carry out migration tests for new food packages incorporated with AgNPs, based on the effective levels for their inclusion in the packaging materials.
ABSTRACT Kefir grains are a symbiotic biomass (yeast and bacteria) commonly used to produce milk probiotic fermented beverages. The aim of this study was to produce a mixed beverage of whole milk and açaí (Euterpe oleracea) berry pulp fermented by two different kefir cultures: one specific for milk and one specific for sugared water, adapted to milk. Based on the fermentation yield, pH and sensory analysis, the culture adapted to milk obtained the best results in a composition (g 100 g-1) of 70 of whole milk and 30 of açaí berry pulp, at room temperature (~25°C), without agitation and fermented for 24 h. The results obtained by this formulation were an increase of 12% in the kefir biomass, 93% of fermentation yield, pH 5.10 and overall sensory acceptance of 7.05.
RESUMO Kefir é uma biomassa simbiótica (leveduras e bactérias) comumente aplicada na obtenção de bebidas fermentadas probióticas de leite. O objetivo deste trabalho foi produzir uma bebida fermentada mista de leite integral e polpa de açaí (Euterpe oleracea) a partir de duas culturas diferentes de kefir: uma original de leite e outra original de água açucarada e adaptada ao leite. Com base na conversão, pH e análise sensorial, os melhores resultados foram obtidos com a cultura adaptada na composição (g 100 g-1) de 70% de leite e 30% de polpa de açaí, sem controle de temperatura (temperatura ambiente ~25° C) e sem agitação e por 24 h de fermentação. Esta formulação apresentou 12% de aumento da biomassa, 93% de conversão, pH 5,10 e uma aceitação global de 7,05.
Amyloglucosidase enzyme was produced by Aspergillus niger NRRL 3122 from solid-state fermentation, using deffated rice bran as substrate. The effects of process parameters (pH, temperature) in the equilibrium partition coefficient for the system amyloglucosidase - resin DEAE-cellulose were investigated, aiming at obtaining the optimum conditions for a subsequent purification process. The highest partition coefficients were obtained using 0.025M Tris-HCl buffer, pH 8.0 and 25ºC. The conditions that supplied the highest partition coefficient were specified, the isotherm that better described the amyloglucosidase process of adsorption obtained. It was observed that the adsorption could be well described by Langmuir equation and the values of Qm and Kd estimated at 133.0 U mL-1 and 15.4 U mL-1, respectively. From the adjustment of the kinetic curves using the fourth-order Runge-Kutta algorithm, the adsorption (k1) and desorption (k2) constants were obtained through optimization by the least square procedure, and the values calculated were 2.4x10-3 mL U-1 min-1 for k1 and 0.037 min-1 for k2 .
A enzima amiloglicosidase foi produzida por Aspergillus niger NRRL 3122 através de fermentação em estado sólido, tendo como substrato farelo de arroz desengordurado. Os efeitos dos parâmetros de processo (pH e temperatura) no coeficiente de partição no equilíbrio, para o sistema amiloglicosidase - resina DEAE-celulose foram investigados, com o objetivo de se obter as melhores condições para um posterior processo de purificação. Os maiores coeficientes de partição foram obtidos usando tampão Tris-HCl 0,025M pH 8,0 e 25°C. Determinadas as condições que forneceram o maior coeficiente de partição obteve-se a isoterma que melhor descrevia o processo de adsorção de amiloglicosidase. Foi verificado que adsorção pode ser bem descrita pela equação de Langmuir e os valores de Qm e Kd foram estimados em 133,0 U mL-1 e 15,4 U mL-1 respectivamente. A partir do ajuste das curvas cinéticas utilizando o método de Runge-Kutta de quarta ordem, obteve-se as constantes de adsorção (k1) e dessorção (k2) através da otimização pelo método dos mínimos quadrados, os valores encontrados foram 2,4x10-3 mL U-1 min-1 para k1 e 0,037 min-1 para k2.
Cutinases (EC 220.127.116.11) are also known as cutin hidrolases. These enzymes share catalytic properties of lipases and esterases, presenting a unique feature of being active regardless the presence of an oil-water interface, making them interesting as biocatalysts in several industrial processes involving hydrolysis, esterification and trans-esterification reactions. They are also active in different reaction media, allowing their applications in different areas such as food industry, cosmetics, fine chemicals, pesticide and insecticide degradation, treatment and laundry of fiber textiles and polymer chemistry. The present review describes the characteristics, potential applications and new perspectives for these enzymes.