Successive membrane separation processes simplify concentration of lipases produced by Aspergillus niger by solid-state fermentation

In this study, we developed a simplified method for producing, separating, and concentrating lipases derived from solid-state fermentation of agro-industrial residues by filamentous fungi. First, we used Aspergillus niger to produce lipases with hydrolytic activity. We analyzed the separation and concentration of enzymes using membrane separation processes. The sequential use of microfiltration and ultrafiltration processes made it possible to obtain concentrates with enzymatic activities much higher than those in the initial extract. The permeate flux was higher than 60 L/m² h during microfiltration using 20- and 0.45-µm membranes and during ultrafiltration using 100- and 50-kDa membranes, where fouling was reversible during the filtration steps, thereby indicating that the fouling may be removed by cleaning processes. These results demonstrate the feasibility of lipase production using A. niger by solid-state fermentation of agro-industrial residues, followed by successive tangential filtration with membranes, which simplify the separation and concentration steps that are typically required in downstream processes.

     

Assessment of two immobilized lipases activity and stability to low temperatures in organic solvents under ultrasound-assisted irradiation

Both stability and catalytic activity of two commercial immobilized lipases were investigated in the presence of different organic solvents in ultrasound-assisted system. In a general way, for Novozym 435, the use of ethanol as solvent led to a loss of activity of 35% after 10 h of contact. The use of iso-octane conducted to a gradual increase in lipase activity in relation to the contact time, reaching a maximum value of relative activity of 126%. For Lipozyme RM IM, after 5 h of exposure, the enzyme presented no residual activity when ethanol was used as solvent. The solvents tert-butanol and iso-octane showed an enhancement of about 20 and 17% in the enzyme activity in 6 h of exposure, respectively. Novozym 435 and Lipozyme IM presented high stability to storage after treatment under ultrasound-assisted system using n-hexane and tert-butanol as solvents.     

Comparative modelling by restraint-based conformational sampling

Background  

Although comparative modelling is routinely used to produce three-dimensional models of proteins, very few automated approaches are formulated in a way that allows inclusion of restraints derived from experimental data as well as those from the structures of homologues. Furthermore, proteins are usually described as a single conformer, rather than an ensemble that represents the heterogeneity and inaccuracy of experimentally determined protein structures. Here we address these issues by exploring the application of the restraint-based conformational space search engine, RAPPER, which has previously been developed for rebuilding experimentally defined protein structures and for fitting models to electron density derived from X-ray diffraction analyses.     

Immunogenetic studies of maternal-fetal relationships: a review: why newborn rhesus monkeys don't get hemolytic disease

The discovery of the Rh blood group factor in humans was made using the red blood cells of rhesus monkeys. Because of its importance to human medicine and immunogenetics, this finding contributed greatly to the appreciation of the importance of nonhuman primates in research. It is now widely recognized that blood group incompatibility between mother and fetus can lead to differential fertility, fetal death, and hemolytic disease of the newborn (HDN).The blood group systems of several nonhuman primate species have been studied in detail and found to be analogous, although not identical, to those of humans. It is therefore surprising that HDN has been reported in only four nonhuman primate species-marmosets, sacred baboons, chimpanzees, and orangutans. Maternal-fetal blood group incompatibility and its consequences have been extensively studied in rhesus monkeys, and these macaques may well be representative of many nonhuman primates. Rhesus monkeys exhibit all five of the conditions that lead to HDN in humans: (1) blood group incompatible matings: (2) transplacental hemorrhage: (3) maternal immunization to blood group alloantigens on fetal erythrocytes: (4) transplacental transfer of maternal antibodies; and (5) coating of the newborn's erythrocytes. Yet, newborns show no clinical or hematological evidence of HDN.We have shown that the rhesus alloantibodies engendered by transplacental immunization do not mediate immune elimination of the newborn's erythrocytes. Evaluation of the maternal antibodies demonstrated that they have low titers and low avidities and perhaps belong to IgG subclasses that do not bind effectively to receptors on phagocytic cells of the rhesus reticuloendothelial system. The newborn's genotype may also affect the expression of allogeneic blood group antigens and thereby help protect the newborn's cells from destruction. These factors together undoubtedly play a major role in the survival of the antibody-coated newborn's RBC and are thus able to account for the absence of HDN in this species.