Douglas de Britto

A Review of the Antimicrobial Activity of Chitosan

Chitosan, a versatile hydrophilic polysaccharide derived from chitin, has a broad antimicrobial spectrum to which gram-negative, gram-positive bacteria and fungi are highly susceptible. In the current review, three possible and accepted antimicrobial mechanisms for chitosan are presented and briefly discussed. The activity dependence on polymeric molecular weight (MW) and degree of acetylation (DA) are described. The chitosan minimum inhibitory concentrations (MIC) are summarized according to recent data found in the literature. The potential to improve inhibitory growth of bacteria by using water soluble chitosan derivatives is also discussed. The data indicate that the effectiveness of chitosan varies and is dependent on species of target microorganisms.

Effect of Carboxymethylcellulose and Plasticizer Concentration on Wetting and Mechanical Properties of Cashew Tree Gum–Based Films

The combination of carboxymethylcellulose (CMC), cashew tree gum and, glycerol as plasticizer was evaluated in the formation and properties of films processed by casting. CMC acts as both a gelling and film-formation agent, yielding samples with reasonable mechanical properties. Increasing the concentration of CMC increased tensile strength, reduced elongation at break, and decreased wettability of the blended films. Microscopy surface observation shows that plasticizer addition reduces cracks in the films. The combination of cashew gum with CMC increases the hydrophobicity characteristic of the films. The plasticizer, even in small amounts, reduces the hydrophobicity thus increasing surface wettability. This study shows that cashew gum/CMC/glycerol–composed films can be considered as potential materials for technological applications.

Propriedades mecânicas e molhabilidade de filmes de zeínas extraídas de glúten de milho

Zeins comprise a group of maize storage proteins (prolamines) that can be extracted via solubization in alcoholic media. Such proteins are highly hydrophobic with elevated degree of polymerization. In the present study, zein type a (molecular mass between 19 and 22 kDa) was extracted from corn gluten meal and characterized concerning the main spectroscopy absorption bands in the infrared region. Cast films were processed by blending zein and oleic acid (OA) as plasticizer. Films with no plasticizer were extremely brittle, and thus impossible to handle or used for mechanical analysis. The addition of 1 or 2% wt OA resulted in significant increase in the elongation length, according to DMA analysis. The presence of the plasticizer led to microscopic surface irregularities and to a reduction in the original hydrophobic characteristics.

Entrapment characteristics of hydrosoluble vitamins loaded into chitosan and N,N,N-trimethyl chitosan nanoparticles

Nanoencapsulation is a process suitable for use in reducing degradation of instable components. In this study, chitosan and trimethyl chitosan with tripolyphosphate were used to nanoencapsulate vitamins C, B9, and B12. Analysis of the particle size showed that for a fix proportion of the polymer tripolyphosphate, the system showed a wide variation in size with the amount of added vitamins: e.g., for vitamin B9, the particle size varied from 150±5 nm to 809±150 nm. The zeta potential confirmed that trimethyl chitosan nanoparticles generally had a lower net positive charge (20 mV) than chitosan nanoparticles (40 mV). The encapsulation efficiency was found to be dependent on nanoparticle structure and vitamin solubility, with vitamin B9 the most efficiently encapsulated (approximately 40%). UV-Visible spectroscopy indicated different release profiles for vitamins C, B9, and B12 in a neutral PBS solution with release rates of 36%, 52%, and 16% after 2, 24, and 4 h, respectively. In conclusion the liberation was found to be slower in acidic media.

Estudo das interações entre o complexo polieletrolítico trimetilquitosana/carboximetilcelulose e Cu+2, ácido húmico e atrazina em solução aquosa

The polyelectrolyte complex (PEC) resulting from the reaction of sodium carboxymethylcellulose (CMC) and N,N,N-trimethylchitosan hydrochloride (TMQ) was prepared and then characterized by infrared spectroscopy and energy dispersive X rays analysis. The interactions involving the PEC and Cu2+ ions, humic acid and atrazine in aqueous medium were studied. From the adsorption isotherms the maximum amount adsorbed (Xmax) was determined as 61 mg Cu2+/g PEC, 171 mg humic acid/g PEC and 5 mg atrazine/g PEC. The results show that the CMC/TMQ complex has a high affinity for the studied species, indicating its potential application to remove them from aqueous media.

Influence of season, drying temperature and extraction time on the yield and chemical composition of ‘marmeleiro’ (Croton sonderianus) essential oil

Abstract The Caatinga biome is a source of hundreds aromatic plants with medicinal, food and cosmetics potential applications. One of them is Croton sonderianus which essential oil chemical composition and yielding were studied in function of season of harvesting, pre-treatment temperature and time of extraction. In average, after Gas Chromatography analysis, the four major components were spathulenol (40%), 1,8-cineole (25%), α-pinene (8%) and caryophyllene oxide (6%), but such percentage varied greatly in function of the three parameters studied. Sample submitted to drying pre-treatment at 40°C and 2 hours of extraction time resulted in the highest yielding. Components such as spathulenol decreased near 20% from the dry to rainy season, while for germacrene D its amounts increased in the period. Such results will give support for C. sonderianus management in the field cultivation and essential oil exploration.

ANALYSIS OF THERMAL AND AQUEOUS SUSPENSION STABILITIES OF CHITOSAN BASED NANOENCAPSULATED VITAMINS

The food nutritional content is reduced as result of vitamins degradation. In order to minimize such losses, the encapsulation technique into polymeric nanoparticles (NPs) could offer an additional protection, extending the stability. The crosslinking formed by the ionic gelation process of chitosan and tripolyphosphate (Chi-TPP) has been widely used as an encapsulating matrix for several chemical compounds. In this way, Chi-TPP was used for encapsulation of C, B9 and B12 vitamins. The stability of the vitamins in NPs was evaluated in aqueous suspension by UV-Visible spectroscopy under different conditions: stored in dark, light exposure and effect of oxygen bubbling. The results indicated that encapsulation had a positive effect in preserving the vitamins, mainly vitamin C. The encapsulation preserved 47% of the initial concentration of vitamin C by the tenth day and around 28% after 17 days. Conversely, in non-encapsulated controls (neutral and acidic medium) the losses were higher, reaching 13% by the tenth day and almost 3% after 17 days of storage in both medium. When exposed to light and O2 the protection provided by the encapsulation was even greater. By thermogravimetric analysis, the pure and the encapsulated vitamins showed distinct thermal behavior confirming Chi-TPP as a potential encapsulation material.