Ana Iraidy S. Brígida

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.

Production of hydroxyapatite–bacterial cellulose nanocomposites from agroindustrial wastes

In the present work, bionanocomposites based on bacterial cellulose (BC) obtained from alternative sources (cashew juice and sisal liquid waste) and hydroxyapatite (HA) were developed. BC–HA composites were prepared through alternate immersion in CaCl2 and Na2HPO4 solutions. Cellulose was successfully produced from the alternative sources of media without the need for additional supplementation and HA crystals that homogeneously precipitated onto the BC surface. The Ca/P ratio ranged from 1.53 to 1.58, indicating the presence of calcium-deficient HA in the composites; this is a phase similar to biological apatite. After immersion into synthetic body fluid, the HA layer formed on the surface of pure BC and the composites, attesting the material’s bioactivity. Moreover, apatite deposition on the composites was up to three times higher than observed on pure cellulose with no significant desorption of apatite from the composites. These results support that the BC derived from agroindustrial wastes have potential to produce nanocomposites of cellulose/HA for use in bone tissue regeneration.

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.

COMPARAÇÃO DA ESPECIFICIDADE DE LIPASES DE DUAS CEPAS DE Aspergillus niger NA HIDRÓLISE ENZIMÁTICA DO ÓLEO DE GIRASSOL

Diversas pesquisas tem estudado a tecnologia de modificacao dos oleos e gorduras e a obtencao de concentrados de acidos graxos poli-insaturados que beneficiem a saude do ser humano. As lipases sao enzimas que catalisam a hidrolise parcial ou total destes triacilglicerois (TAGs) produzindo acidos graxos livres (AGLs), diacilglicerol (DAG), monoacilglicerol (MAG) e glicerol. Neste trabalho, as enzimas produzidas pela cepa mutante Aspergillus niger 11T53A14 e pela cepa selvagem Aspergillus niger C foram utilizadas para a hidrolise do oleo de girassol. As lipases foram caracterizadas quanto a sua espeficidade em relacao a diferentes p-nitrofenil esteres e aplicadas na hidrolise de oleo de girassol. As condicoes da hidrolise enzimatica do oleo de girassol foram: proporcao molar de agua:oleo (8:1); carga da lipase de 5 U/g de oleo; 50°C e agitacao orbital de 150 rpm. Os acidos graxos livres foram quantificados em titulador automatico com NaOH 0,05 N. Os melhores resultados de hidrolise foram obtidos com extrato bruto de A. niger C, que apresentaram 228 mM de acidos graxos livres em 5,5 horas de reacao.