Design of bioreactor based on immobilized laccase on silica-chitosan support for phenol removal in continuous mode.

A silica-chitosan support was employed for laccase immobilization. The hybrid support was obtained using calcium ion as linking agent that coordinates silanol and hydroxyl groups of chitosan. The insoluble biocatalyst was then packed in a column and used in a flow system for phenol removal. The immobilized enzyme reactor (IMER) showed a good storage stability (70 % of activity in 70 days) and good reusability (90-50 % of catalytic activity at the 4th reuse in function of chitosan type). The best performance for the phenol removal was obtained with a low molecular weight chitosan from crab shells at pH 5 and with a flow rate of 0.7 mL/min. The apparent Michaelis-Menten (Vmaxapp, Kmapp) and the inherent (Vmaxinh, Kminh) constants were also determined to evaluate the influence of the phenol structure on the performance of the system. The enzymatic oxidation of a phenol mixture (4-methylcatechol, catechol, caffeic acid, syringic acid, vanillic acid, p-coumaric acid, and tyrosol) was followed for 21 h in a continuous mode by HPLC. The phenol mixture removal of 90 % was also confirmed by Folin-Ciocalteu assay.

Silica-chitosan hybrid support for laccase immobilization.

The aim of this study was to optimize the laccase immobilization on a silica/chitosan composite support. The innovative method proposed is based on the use of Ca(II) as a linker of the support precursors. In addition for the laccase immobilization the glycosidic part of enzyme is oxidized by periodate in order to form aldehydes reactive towards the NH2 groups of chitosan. The immobilized laccase presents a good storage stability (7 months 40% residual activity) and a good affinity towards ABTS substrate (Kmapp 0.008 mM, Vmaxapp = 0.0034 µmol/min). Furthermore, the biocatalyst showed optimum pH 3 and optimum incubation temperature of 50 °C.

Correction to: Structural modeling of a novel TERC variant in a patient with aplastic anemia and short telomeres.

The original version of this article contained a mistake in the affiliation of E. Bellacchio. Correct affiliation is presented here.

Should pre-transfusion screening RBC panels contain Wr(a+) cells?

Sometimes commercial RBC sets for the screening of irregular antibodies contain Wr(a+) cells. The aim of this study was to define the usefulness of employing RBC sets for the screening of irregular antibodies containing Wr(a+) cells in pre-transfusion tests. Anti-Wr(a) is a relatively common naturally occurring antibody in candidates to blood transfusion, although the risk of receiving a non-compatible unit is low. We have studied both the incidence of Wr(a) antibodies and the effects of having a Wr(a+) cell in the screening test on routine work in an unselected population of 787 patients requiring RBC transfusion and in 151 new blood donors. Irregular antibodies were found in 64 sera, 58 of which were specific for Wr(a) , 46 (5·8%) and 12 (7·9%) in patients and donors, respectively. The positive tested sera contained specific IgM in 16 cases, IgM + IgG in 13 cases and IgG in 27 cases. Anti-Wr(a) can usually be detected during cross-match procedures; therefore, the presence of Wr(a+) cells in pre-transfusion screening of blood recipients is not justified and it causes an undue increase in cost and time to unit release. Moreover, because of the rare association between anti-Wr(a) and haemolytic transfusion reaction, the use of Wr(a+) RBC-containing sets is also questionable in the countries that do not perform pre-transfusion cross-match tests.