D-amino acid oxidase from Trigonopsis variabilis: immobilisation of whole cells in natural polymeric gels for glutaryl-7-aminocephalosporanic acid production

The enzymatic oxidation of cephalosporin C to glutaryl-7-amminocephalosporanic acid (glutaryl-7-ACA) was carried out utilizing permeabilized whole cells of the yeast Trigonopsis variabilis entrapped in Ca-alginate beads. The biomass, cultured in a rich medium containing D,L methionine and harvested after 72 h of growth, exhibited high levels of D-aminoacid oxidase activity. Prior to use, thewho,lke cells were permeabilized with four freeze-thawing cycles and immobilized in polysaccharide matrices, such as Ca-alginate and K- carrageenan, and in an insolubilised gelatin gel. The best results in terms of activity yield and storage stability were obtained with cells entrapped in Ca-alginate beads. These cells were utilized for glutaryl-7-ACA production in a continuous stirred batch reactor (CSTR) and in a packed bed reactor working in a plug flow reactor (PFR), using 50 mm Cephalosporin C as substrate. The performances of the two systems were compared. The overall on a void volume basis) were 1.63 g and 255 mg of glutaryl-7-ACA h-1 in the PFR and in CSTR, respectively

Influence of very low doses of mediators on fungal laccase activity - nonlinearity beyond imagination

Laccase, an enzyme responsible for aerobic transformations of natural phenolics, in industrial applications requires the presence of low-molecular substances known as mediators, which accelerate oxidation processes. However, the use of mediators is limited by their toxicity and the high costs of exploitation. The activation of extracellular laccase in growing fungal culture with highly diluted mediators, ABTS and HBT is described. Two high laccase-producing fungal strains, Trametes versicolor and Cerrena unicolor, were used in this study as a source of enzyme. Selected dilutions of the mediators significantly increased the activity of extracellular laccase during 14 days of cultivation what was distinctly visible in PAGE technique and in colorimetric tests. The same mediator dilutions increased demethylation properties of laccase, which was demonstrated during incubation of enzyme with veratric acid. It was established that the activation effect was assigned to specific dilutions of mediators. Our dose-response dilution process smoothly passes into the range of action of homeopathic dilutions and is of interest for homeopaths

L'APPROCCIO METODOLOGICO

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Effect of polyvinylalcohols on the thermostability of lipase from Candida rugosa

Lipase from Candida rugosa was stabilized against thermal inactivation in the presence of polyvinylalcohols (PVA) of different molecular weights. The apparent rate constant of the lipase inactivation, kd, at 49 °C is 0.049/min and 0.022/min in the absence and in the presence of PVA (mol wt 22,000), respectively. The improvement of the lipase thermostability by adding PVA was confirmed by differential scanning calorimetry. The presence of PVA had also an effect on the hydrolytic activity of the enzyme. Furthermore, lipase was modified by covalent linkage to PVA by means of an original procedure. With respect to the native enzyme, the modified lipase has a slightly lower specific activity, but it is more stable against heat denaturation (kd 0.032/min at 49 °C)

Pediatric Fatty Liver and Obesity: Not Always Justa Matter of Non-Alcoholic Fatty Liver Disease

Obesity-related non-alcoholic fatty liver disease (NAFLD) represents the most common cause of pediatric liver disease due to overweight/obesity large-scale epidemics. In clinical practice, diagnosis is usually based on clinical features, blood tests, and liver imaging. Here, we underline the need to make a correct differential diagnosis for a number of genetic, metabolic, gastrointestinal, nutritional, endocrine, muscular, and systemic disorders, and for iatrogenic/viral/autoimmune hepatitis as well. This is all the more important for patients who are not in the NAFLD classical age range and for those for whom a satisfactory response of liver test abnormalities to weight loss after dietary counseling and physical activity measures cannot be obtained or verified due to poor compliance. A correct diagnosis may be life-saving, as some of these conditions which appear similar to NAFLD have a specific therapy. In this study, the characteristics of the main conditions which require consideration are summarized, and a practical diagnostic algorithm is discussed

Increase in Beta-galactosidase activity in a non-isothermal bioreactor utilizing immobilized cells of Kluyveromyces fragilis: fundamentals and applications.

The β-galactosidaseactivity of Kluyveromyces fragiliscellsimmobilized in a kappa carrageenan gel was studied in abioreactor functioning under isothermal and non-isothermal conditions. We observed an increase in enzyme activity which was found to be proportional to the intensity of the temperature gradient applied across the biocatalytic membrane, as well as to the average temperature of the bioreactor. The efficiency of such anon-isothermalbioreactor was calculated with respect to the yield of abioreactor working under comparable isothermal conditions and was evaluated in terms of reduction of processing times in industrial applications. The possibility that enzyme activity in living cells is affected by non-isothermal conditions naturally existing owing to metabolic heat production is also discussed