Green coconut fiber: a novel carrier for the immobilization of commercial laccase by covalent attachment for textile dyes decolourization.

Commercial laccase formulation was immobilized on modified green coconut fiber silanized with 3-glycidoxypropyltrimethoxysilane, aiming to achieve a cheap and effective biocatalyst. Two different strategies were followed: one point (pH 7.0) and multipoint (pH 10.0) covalent attachment. The influence of immobilization time on enzymatic activity and the final reduction with sodium borohydride were evaluated. The highest activities were achieved after 2 h of contact time in all situations. Commercial laccase immobilized at pH 7.0 was found to have higher activity and higher affinity to the substrate. However, the immobilization by multipoint covalent attachment improved the biocatalyst thermal stability at 50 °C, when compared to soluble enzyme and to the immobilized enzyme at pH 7.0. The Schiff's bases reduction by sodium borohydride, in spite of causing a decrease in enzyme activity, showed to contribute to the increase of operational stability through bonds stabilization. Finally, these immobilized enzymes showed high efficiency in the continuous decolourization of reactive textile dyes. In the first cycle, the decolourization is mainly due to dyes adsorption on the support. However, when working in successive cycles, the adsorption capacity of the support decreases (saturation) and the enzymatic action increases, indicating the applicability of this biocatalyst for textile wastewater treatment.

Whey hydrolysate-based ingredient with dual functionality: From production to consumer's evaluation.

The aim of the present study concerns the development, characterization and sensory evaluation of a dual-functional whey hydrolysate. Four concentrations of commercial pepsin (0.48%, 0.95%, 1.43%, 1.91% w/w) were evaluated. The hydrolyses curves and the Reversed-Phase High Performance Liquid Chromatography analyses showed a direct relationship between enzyme concentration and degree of hydrolysis. Through mass spectrometry 21 peptides were identified and 5 of them have never been described in the literature before. The hydrolysate produced (PC3) induced a vascular relaxation of 65.02% in phenylephrine-contracted rat aortic rings. PC3 powder presented a homogeneous aspect with a mean particle size of 86.39 µm, high water solubility (>92%) in a wide pH range (1-12) and an increase of 33% in oil absorption capacity, when compared to the unhydrolyzed product. Sensory analysis showed a high acceptance (7.6 in a 9-point hedonic scale) of the hydrolysate among 100 consumers. The results brought the possibility of developing a whey hydrolysate with high vasorelaxant activity, great technological properties and sensory appeal, as an interesting dual-functional ingredient to be incorporated into food products.

Coupling of ultrafiltration and enzymatic hydrolysis aiming at valorizing shrimp wastewater.

The objective of this work was to obtain a protein hydrolysate from the wastewater generated during shrimp cooking, by coupling ultrafiltration and enzymatic hydrolysis processes. Initially, the effluent was concentrated by ultrafiltration, reaching a protein concentration factor of 3.2. The concentrated effluent was then enzymatically hydrolyzed, aiming at obtaining peptides with antioxidant capacity. The effects of some process variables--temperature (55-75 °C), pH (7-9) and enzyme/substrate (E/S) ratio (0.1-2.5%)--on the degree of hydrolysis and the antioxidant capacity were evaluated. The increase in temperature and pH resulted in lower degree of hydrolysis and higher antioxidant capacity. The conditions selected as the most suitable were: temperature of 75 °C, pH of 9.0 and E/S ratio of 0.1%. The hydrolysates produced at these conditions were also evaluated for total amino acid content and electrophoretic profile, showing a suitable amount of essential amino acids that covers the recommended daily needs.

Improvement of polyvinyl alcohol properties by adding nanocrystalline cellulose isolated from banana pseudostems.

Cellulose nanocrystals (CNCs) isolated from banana pseudostems fibers (BPF) of the Pacovan variety were used as fillers in a polyvinyl alcohol (PVOH) matrix to yield a nanocomposite. The fibers from the external fractions of the BPF were alkaline bleached and hydrolyzed under acidic conditions (H2SO4 62% w/w, 70 min, 45 °C) to obtain CNCs with a length (L) of 135.0 ± 12.0 nm and a diameter (D) of 7.2 ± 1.9 nm to yield an aspect ratio (L/D) of 21.2. The CNCs were applied to PVOH films at different concentrations (0%, 1%, 3%, and 5% w/w, dry basis). With higher concentrations of CNCs, the water-vapor barrier of the films increased, while the optical properties changed very little. Increasing the concentration of the CNCs up to 3% significantly improved the mechanical properties of the nanocomposite.