Phase Behaviour and Miscibility Studies of Collagen/Silk Fibroin Macromolecular System in Dilute Solutions and Solid State

Miscibility is an important issue in biopolymer blends for analysis of the behavior of polymer pairs through the detection of phase separation and improvement of the mechanical and physical properties of the blend. This study presents the formulation of a stable and one-phase mixture of collagen and regenerated silk fibroin (RSF), with the highest miscibility ratio between these two macromolecules, through inducing electrostatic interactions, using salt ions. For this aim, a ternary phase diagram was experimentally built for the mixtures, based on observations of phase behavior of blend solutions with various ratios. The miscibility behavior of the blend solutions in the miscible zones of the phase diagram was confirmed quantitatively by viscosimetric measurements. Assessing the effects of biopolymer mixing ratio and salt ions, before and after dialysis of blend solutions, revealed the importance of ion-specific interactions in the formation of coacervate-based materials containing collagen and RSF blends that can be used in pharmaceutical, drug delivery, and biomedical applications. Moreover, the conformational change of silk fibroin from random coil to beta sheet, in solution and in the final solid films, was detected by circular dichroism (CD) and Fourier transform infrared spectroscopy (FTIR), respectively. Scanning electron microscopy (SEM) exhibited alterations of surface morphology for the biocomposite films with different ratios. Surface contact angle measurement illustrated different hydrophobic properties for the blended film surfaces. Differential scanning calorimetry (DSC) showed that the formation of the beta sheet structure of silk fibroin enhances the thermal stability of the final blend films. Therefore, the novel method presented in this study resulted in the formation of biocomposite films whose physico-chemical properties can be tuned by silk fibroin conformational changes by applying different component mixing ratios

Ações voltadas para a construção do Núcleo de Agroecologia da Embrapa Milho e Sorgo.

O projeto Constituição do Núcleo de Agroecologia na Embrapa Milho e Sorgo (EMS) é uma ação decorrente da Política Nacional de Agroecologia e Produção Orgânica. A ampliação da percepção ambiental foi considerada fundamental para a sensibilização e promoção da Agroecologia na EMS, que dispõe de uma fazenda de quase 2.000 ha, com Cerrado e Mata Atlântica. Muitos empregados, cumprindo tarefas rotineiras, estão alheios às riquezas naturais em seu entorno próximo. Foram propostas e executadas as seguintes ações: campanhas de produção e plantio de mudas de Cratylia argentea; curso de sistema agroflorestal; curso de produção de mudas florestais; pesquisa sobre percepção dos empregados com relação aos frutos da EMS; e campanha para promoção da venda direta de hortaliças das hortas comunitárias aos empregados da EMS. Ao se envolver na formulação e na aplicação de políticas públicas em Agroecologia e produção orgânica, fica ressignificada a prática da pesquisa agropecuária e reafirma-se a função social histórica da Embrapa como agente de mudança.Edição dos anais do VI Congresso Latino-Americano de Agroecologia, Brasília, DF, 2017

Photosynthetic pigments and quantum yield of West Indian cherry under salt stress and NPK combinations

Abstract West Indian cherry cultivation has proved to be an important economic activity in northeastern Brazil. However, irrigation with brackish waters limits cultivation, requiring new strategies to minimize the effect of salt stress. In this context, the present study aimed to evaluate the effect of nitrogen (N), phosphorus (P), and potassium (K) combinations on the photosynthetic pigments and quantum yield of West Indian cherry cultivated under salt stress, in the second year of production. The assay was conducted in a protected environment by adopting an experimental design in randomized blocks, with treatments distributed in a 2×10 factorial arrangement referring to two electrical conductivity levels of irrigation water - ECw (0.6 and 4.0 dS m-1) and 10 NPK fertilization combinations - FC (80-100-100; 100-100-100; 120-100-100; 140-100-100; 100-80-100; 100-120-100; 100-140-100; 100-100-80; 100-100-120, and 100-100-140% of the recommendation, in the second year of production), with three replications, each consisting of one plant. Irrigation with the electrical conductivity of 4.0 dS m-1 negatively affected the synthesis of photosynthetic pigments and the photochemical efficiency of the West Indian cherry cv. Flor Branca. The NPK combinations did not attenuate the effects of salt stress on the analyzed variables. However, the combinations referring to 120-100-100%, 140-100-100%, and 100-120-100% of NPK recommendation improved the quantum yield of photosystem II by reducing the initial fluorescence and increasing the maximum fluorescence of the West Indian cherry cv. Flor Branca