J. P. S. Morais

Extraction and characterization of nanocellulose structures from raw cotton linter

This study aimed to characterize nanocellulose extracted from cotton (Gossypium hirsutum) linters. The nanocellulose was subjected to electronic microscopy, thermal analysis, X-ray diffractometry, light scattering, and contact angle. The properties of the nanocellulose are considerably different from the linter. The acidic hydrolyses applied to extract the nanocrystals increased the crystallinity index and the hydrophilicity and decreased the thermal stability. On average, the nanocrystals were 177 nm long and 12 nm wide, with an aspect ratio of 19 when measured by microscopy. The light scattering results were coherent with the crystal dimensions. Cotton linter is a potential source of nanocellulose crystals, particularly to be used in the production of hydrophilic nanocomposites. Extraction of nanocellulose from raw cotton linter does not require pulping.

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.

A novel green approach for the preparation of cellulose nanowhiskers from white coir

The aim of this work was to optimize the extraction of cellulose nanowhiskers (CNW) from unripe coconut husk fibers (CHF). The CHF was delignified using organosolv process, followed by alkaline bleaching (5% (w/w) H2O2+4% (w/w) NaOH; 50°C, 90 min). The CHF was subsequently hydrolyzed with 30% (v/v) sulfuric acid (60°C, 360 min). The process yielded a partially delignified acetosolv cellulose pulp and acetic black liquor, from which the lignin was recovered. The CNW from the acetosolv pulp exhibited an average length of 172±88 nm and a diameter of 8±3 nm, (aspect ratio of 22±8). The surface charge of the CNW was -33 mV, indicating a stable aqueous colloidal suspension. The nanocrystals presented physical characteristics close to those extracted from cellulose pulp made by CHF chlorine-pulping. This approach offers the additional advantage of extracting the lignin as an alternative to eradication.

Bacterial cellulose nanocrystals produced under different hydrolysis conditions: properties and morphological features

Bacterial cellulose (BC) is a polymer with interesting physical properties owing to the regular and uniform structure of its nanofibers, which are formed by amorphous (disordered) and crystalline (ordered) regions. Through hydrolysis with strong acids, it is possible to transform BC into a stable suspension of cellulose nanocrystals, adding new functionality to the material. The aim of this work was to evaluate the effects of inorganic acids on the production of BC nanocrystals (BCNCs). Acid hydrolysis was performed using different H2SO4 concentrations and reaction times, and combined hydrolysis with H2SO4 and HCl was also investigated. The obtained cellulose nanostructures were needle-like with lengths ranging between 622 and 1322nm, and diameters ranging between 33.7 and 44.3nm. The nanocrystals had a crystallinity index higher than native BC, and all BCNC suspensions exhibited zeta potential moduli greater than 30mV, indicating good colloidal stability. The mixture of acids resulted in improved thermal stability without decreased crystallinity.

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.

Avaliação de substratos e adubos orgânicos na aclimatização de plântulas de Heliconia psittacorum

The objective of this work was to evaluate the efficiency of three organic substrates, carbonised rice hull, dry and green coir dust, and two fertilizers, Vitasolo® and earthworm humus, in the acclimatization of plantlets of Heliconia psittacorum L., obtained from micropropagation. After 75 days, the height of the plants, diameter of pseudo-stem, number of leaves and area of the third leaf were evaluated. The rice hull was more efficient than the coir dust (dry or green); the green coir dust was more efficient than dry coir dust; and the humus was more efficient than Vitasolo®.

In vitro multiplication of ornamental pineapple by shoot etiolation and regeneration

The in vitro multiplication of etiolated nodal segments was evaluated for Ananas comosus var. erectifolius shoots production. Stems were inoculated in the following media: MS without growth regulator; MS + 10 µM of indolbutiric acid (IBA); MS + 10 µM of naphtalenacetic acid (NAA); MS + 10 µM of indolacetic acid (IAA); and stored in darkness at 25±2oC. 60 days after inoculation, the number of etiolated shoots/stem; number of nodes/etiolated shoot; etiolated shoot length, internode length and total number of nodes/stem were evaluated. The medium MS + 10 µM of NAA showed the highest values of number of etiolated shoots and total number of nodes/etiolated shoot. For shoot regeneration, nodal segments from in vitro etiolated stems with two nodes were inoculated in the following media: MS without growth regulator; MS + 4.44 µM of 6-benzylaminopurine (BA); MS + 8.88 µM of BA; MS + 13.32 µM of BA. The flasks were incubated under photoperiod of 16 hours, at 25±2oC. At 30 days of culture, the number of regenerated shoots/explant did not differ in the tested media. At 45 and 60 days of culture, the media with BAP induced higher number of regenerated shoots per node, differing statistically from the control.

Zein films with unoxidized or oxidized tannic acid

BACKGROUND Corn zein is a predominatly hydrophobic protein, forming films with relatively good water resistance. Tannic acid, especially in its oxidized form, is supposed to cross-link proteins including zein, which may be explored to further enhance the water resistance of zein films. The effects of different contents (0-8 wt%) of unoxidized and oxidized tannic acid (uTA and oTA, respectively) on the properties of zein films at different pH values (4-9) were studied, according to central composite designs. RESULTS Increasing tannic acid contents and pH values resulted in decreased water solubility and increased tensile strength and modulus of films. The presence of tannic acid provided the films with a yellowish color and increased opacity. Paired t-tests indicated that oTA films presented higher tensile strength, lower water vapor permeability and lower water solubility than uTA films. CONCLUSION Higher tannic acid contents and pH values resulted in films with better overall physical properties, which might be ascribed to cross-linking, although the films were still not water resistant. The resulting films have potential to be used for food packaging and coating applications.

Thermal and Chemical Properties of Gelatin from Tilapia (Oreochromis niloticus) Scale

ABSTRACT Gelatin from the scale of Nile tilapia was extracted and characterized chemically, thermally, and structurally. Scales of Nile tilapia were subjected to acid pretreatment and extraction with water at 60°C. The process yielded 12.1% (m/m) on a dry basis. The 6.67% gelatin solution had a gel strength of 233.5 ± 14g. The amino acid composition revealed that 20.02% was comprised of imino acids and glycine (34.49%) as the most abundant amino acids. The scale gelatin had α1, α2, and β subunits and was thermally stable up to 200ºC. The Fourier transform infrared spectrum showed absorption in the regions of amides A, I, II, and III. The characterization of tilapia scale gelatin showed that the obtained product was similar to commercial gelatin, thereby demonstrating its potential application.

Caracterização morfológica de nanocristais de celulose por microscopia de força atômica

O isolamento de nanocristais de celulose (CNCs) de fibras vegetais e uma alternativa promissora para sua aplicacao como reforco em matrizes polimericas. A caracterizacao dos CNCs e fundamental para a confiabilidade da tecnica, alem de determinar as aplicacoes possiveis a partir de cada tipo de fibra. A partir da tecnica de microscopia de forca atomica, um estudo da morfologia e distribuicao dos CNCs de semente de manga, vagem de algaroba, pseudocaule da bananeira e fibra do mesocarpo de dende foi realizado neste trabalho. Os CNCs foram obtidos via reacao hidrolitica com acido sulfurico em concentracoes que variaram de acordo com a fonte da fibra. Os resultados obtidos revelaram dimensoes variando de 300 a 500 nm em comprimento e 4 a 16 nm em diâmetro. A apresentacao morfologica em forma de agulha demonstrou que o isolamento das fibras de celulose em CNCs foi efetiva. A razao de aspecto associada a formacao cilindrica em agulha dos CNCs isolados evidenciou o alto potencial das fontes de dende e de vagem de algaroba para o reforco de bionanocompositos.