Biomedical subjects

L Giorno

Publications and source records attributed to L Giorno.

6 recordsLinked to original sources

PubMed2005

Effects of organic solvents on ultrafiltration polyamide membranes for the preparation of oil-in-water emulsions.

Hydrophilic ultrafiltration membranes made of polyamide with molecular weight cutoff 10 and 50 kDa have been studied for the preparation of oil-in-water emulsions by a cross-flow membrane emulsification technique. Isooctane and phosphate buffer were used as disperse and continuous phase, respectively. The permeation of apolar isooctane through the polar hydrophilic membrane was achieved by pretreatment of membranes with a gradient of miscible solvents of decreasing polarity to remove water from the pores and replace it with isooctane. Four different procedures were investigated, based on the solvent mixture percentage and contact time with membranes. After pretreatment, the performance of the membranes in terms of pure isooctane permeate flux and emulsion preparation was evaluated. The influence of organic solvents on polyamide (PA) membranes has been studied by SEM analysis, which showed a clear change in the structure and morphology of the thin selective layers. The effects proved stronger for PA 10 kDa than for 50 kDa. In fact, similar pretreatment procedures caused larger pore size and pore size distribution for PA 10 kDa than for 50 kDa. The properties of emulsions in terms of droplet size distribution reflected the membrane pore sizes obtained after pretreatment. The correlation between pore size and droplet size, for the physicochemical and fluid dynamic conditions used, has been evaluated.

Journal Article↗

PubMed2005

Diffusive and convective transport through hollow fiber membranes for liver cell culture.

For an efficient membrane bioreactor design, transport phenomena determining the overall mass flux of metabolites, catabolites, cell regulatory factors, and immune-related soluble factors, need to be clarified both experimentally and theoretically. In this work, experiments and calculations aimed at discerning the simultaneous influence of both diffusive and convective mechanisms to the transport of metabolites. In particular, the transmembrane mass flux of glucose, bovine serum albumin (BSA), APO-transferrin, immunoglobulin G, and ammonia was experimentally measured, under pressure and concentration gradients, through high-flux microporous hydrophilic poly-ether-sulphone (PES-HFMs) and poly-sulphone hollow fiber membranes (PS-HFMs). These data were analyzed by means of a model based on the mechanism of capillary pore diffusion, assuming that solute spherical molecules pass through an array of solvent-filled cylindrical pores with a diffusive permeation corrected for friction and steric hindrances. Additionally, resistances to the mass transfer were taken into account. Convective permeation data were discussed in terms of morphological properties of the polymeric membranes, molecular Stokes radius, and solute-membrane interactions according to information given by contact angle measurements. The observed steady-state hydraulic permeance of PS-HFMs was 0.972 L/m2hmbar, about 15.6-fold lower than that measured for PES-HFMs (15.2 L/m2h); in general, PS-HFMs provided a significant hindrance to the transport of target species. Diffusion coefficients of metabolites were found to be similar to the corresponding values in water through PES-HFMs, but significantly reduced through PS-HFMs (D(Glucose)(Membrane)=2.8x10(-6)+/-0.6x10(-6)cm2/s, D(BSA)(Membrane)=6.4 x 10(-7)+/-1 x 10(-7)cm(/s, D(Apotransferrin)(Membrane)=2.3 x 10(-7)+/-0.25 x 10(-7)cm2/s).

Ammonia↗

PubMed2003

Use of stable emulsion to improve stability, activity, and enantioselectivity of lipase immobilized in a membrane reactor.

The enantiocatalytic performance of immobilized lipase in an emulsion membrane reactor using stable emulsion prepared by membrane emulsification technology was studied. The production of optical pure (S)-naproxen from racemic naproxen methyl ester was used as a model reaction system. The O/W emulsion, containing the substrate in the organic phase, was fed to the enzyme membrane reactor from shell-to-lumen. The enzyme was immobilized in the sponge layer (shell side) of capillary polyamide membrane with 50 kDa cut-off. The aqueous phase was able to permeate through the membrane while the microemulsion was retained by the thin selective layer. Therefore, the substrate was kept in the enzyme-loaded membrane while the water-soluble product was continuously removed from the reaction site. The results show that lipase maintained stable activity during the entire operation time (more than 250 h), showing an enantiomeric excess (96 +/- 2%) comparable to the free enzyme (98 +/- 1%) and much higher compared to similar lipase-loaded membrane reactors used in two-separate phase systems (90%). The results demonstrate that immobilized enzymes can achieve high stability as well as high catalytic activity and enantioselectivity.

Bioreactors↗

PubMed2001

Study of an enzyme membrane reactor with immobilized fumarase for production of L-malic acid.

The conversion of fumaric acid into L-malic acid by fumarase immobilized in a membrane reactor was analyzed experimentally. The enzyme was entrapped in asymmetric capillary membranes made of polysulfone. The performance of the reactor was evaluated in terms of conversion degree, reaction rate, and stability. The influence of operating conditions, such as amount of immobilized enzyme, substrate concentration, residence time, and axial flow rate, were investigated. The kinetic parameters K(m), V(max), and k(+2) were also measured. The stability of the immobilized enzyme was very good, showing no activity decay during more than 2 weeks of continuous operation.

Animals↗

PubMed2000

Biocatalytic membrane reactors: applications and perspectives.

Membranes and biotechnological tools can be used for improving traditional production systems to maintain the sustainable growth of society. Typical examples include: new and improved foodstuffs, in which the desired nutrients are not lost during thermal treatment; novel pharmaceutical products with well-defined enantiomeric compositions; and the treatment of waste-water, wherein pollution by traditional processes is a problem.

Animals↗

PubMedDate not supplied

Enzymatic hydrolysis of DNA using a membrane bioreactor.

Aim of this work was a kinetic study of the deoxyribonuclease I (E.C. 3.1.21.1.) reaction in several conditions. Optimal reaction conditions with enzyme free in solution were determined. DNase activity was studied as function of several parameters such as pH, enzyme concentration, substrate concentration, cofactor concentration. The Km value of the free enzyme was also determined. Subsequently, the possibility to carry out the reaction in systems in which the enzyme was immobilized on the inner surface of the polymeric membranes was evaluated and realized. Experimental procedures, in these new conditions, permitted to determine the mass of immobilized enzyme and the percentage of the reaction product recovery. Results showed that the immobilization procedure determines a decay of the initial activity of enzyme, but there is an important increase of enzyme stability.

Animals↗