ObstractThis study investigated the effects of low concentrations of sericin (≤ 1.5 wt%) in starch-poly(butylene-adipate-co-terephthalate) (PBAT) films. The films were produced by blown extrusion and mechanical, barrier and structural properties were determined. Films containing 1.0 and 1.5 wt% sericin showed higher tensile strength (6.41 and 6.59 MPa) and Young's modulus (90.88 and 132.71 MPa) compared with film without sericin (4.76 MPa and 18.64 MPa). When 0.5 wt% of sericin was used, the elongation was reduced by 62%. The addition of sericin in a concentration of 1.5% (w/w) decreased the water vapor permeability of films from 7.55 to 5.94 g (m s Pa) -1 , likely due to the formation of a more homogeneous and compact matrix. Based on these results, a mechanism of action is proposed, whereby sericin acts at the interface of the polymers (starch and PBAT), reducing the interfacial tension and enhancing compatibility.
The synthesis of ethyl-oleate by the lipase from the newly isolated strain Burkholderia cepacia LTEB11 in three different systems has been studied Á immobilization on a hydrophobic support (Accurel EP 100 † ), encapsulation in reverse micelles, and direct addition of powdered free enzyme to the reaction medium. The immobilized enzyme performed best, giving a 70% ester yield in 10 h, this yield being fivefold greater than that obtained for reversed micelles, and two and a half times greater than that obtained for direct addition. An increase in the amount of immobilized enzyme preparation added gave a 100% ester yield in 3 h. The immobilized preparation was quite stable, giving a 100% yield of ethyl-oleate during 11 repeated reactions, and 50% yield after 24 reactions. These results suggest that the lipase of our strain of B. cepacia LTEB11 immobilized on Accurel has good potential for application in biocatalysis in organic media.
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