Fungal Growth Control by Chitosan and Derivatives

Chitin and chitosan are aminoglucopyranans composed of N-acetyl-D-glucosamine (GlcNAc) and glucosamine (GlcN) residues and are renewable resources currently being studied by academic and industrial groups owing to their attractive properties and biological activities. Chitosans have been indicated for the preservation of foods, juices and other material from microbial deterioration due their action against different groups of microorganisms, such as bacteria, yeast and fungi. Studies on coating of fruits and vegetables and defensive plant mechanism studies have been described in the literature. There is a worldwide trend to explore new alternatives that can control postharvest pathogenic diseases, giving priority to methods that reduce disease incidence and avoid negative and side effects on human health as a result of the excessive application of synthetic fungicides. Thus, alternative approaches are necessary to maintain the marketable quality of fresh fruits. The antifungal activities of chitosan and its derivatives in vitro, preharvest and postharvest studies are reviewed in this chapter. The abilities of chitosan and its derivatives to elicit resistance reactions in plants and its action in the production and viability of fungal spores is reported. Finally, the chapter is concluded, with the possible mechanisms, suggested in the literature for the antifungal activity of chitosan

Physicochemical Characterization of Thermally Treated Chitosans and Chitosans Obtained by Alkaline Deacetylation

The thermal depolymerization of chitosan and alkaline deacetylation of chitin were characterized by measurement of viscosity, gel permeation chromatography (GPC), potentiometric titration (PT), and proton nuclear magnetic resonance spectroscopy (H1 NMR). The depolymerization rates (DR) measured by kinematic viscosity (KV), apparent viscosity (AV), and GPC (Mw) until 4 h of treatment were DRKV=21.9, DRAV=25.5, and DRMw=23.3% h-1 and for 5 to 10 h of treatment they decreased slowly to produce of DRKV=0.545, DRAV=0.248, and DRMw=1.11% h-1. The mole fraction of N-acetylglucosamine residues FA of chitosans was not modified after 10 h of thermal treatment at 100°C. The initial FA values of chitosan without any treatment were FAPT=0.21 and FAHNMR1=0.22 and of chitosan treated for 10 h were FAPT=0.27 and FAHNMR1=0.22. The variables used to characterize the depolymerization process showed a good correlation. Six hours of thermal treatment as sufficient to obtain chitosans with a molar mass 90% smaller than that of the control chitosan without treatment

Cell viability evaluation of vero cells viability cultured on different chitosan films: development of functional biodressings possibilities

Os biomateriais utilizados na medicina regenerativa devem ter biocompatibilidade e ser atóxicos, pois são utilizados em contato com tecidos vivos para reparo ou reposição. Portanto, eles devem fornecer um microambiente adequado para ex vivocultura de células. A quitosana é um biomaterial muito utilizado em pesquisas de cultura de células por ser atóxico, biocompatível, biodegradável, apresentar alta hidrofilicidade e apresentar importantes características antibacterianas. Este trabalho estudou a interação de células VERO com filmes de quitosana produzidos com diferentes agentes de reticulação, avaliando a viabilidade e morfologia celular. Os ensaios foram seguidos durante 96 horas para análise da proliferação celular, viabilidade e morfologia. As células apresentaram desenvolvimentos distintos nos diferentes filmes, sendo o filme com ácido acético o menos adequado para cultivo apresentando viabilidade celular de 58%, por outro lado, filmes feitos a partir de soluções de quitosana com ácido lático ou cítrico tiveram viabilidade celular em torno de 70% . Portanto, filmes de quitosana podem ser explorados como biomateriais para a produção de biodressing

Changes in hyphal morphology due to chitosan treatment in some fungal species

In this work, changes in the hyphal morphology due to chitosan treatment in some fungal species were studied. Scanning electron microscope (SEM) observations revealed that chitosans with molar fraction of acetyl groups (F A 0.16 and 0.18) and degree of polymerization (DP 1,089 and 1,242) had a direct effect on the morphology of the chitosan-treated fungi, reflecting its potential for causing a delay in the growth of Alternaria alternata (500 µg × mL-1), Botrytis cinerea (1,000 µg × mL-1), Penicillium expansum (1,000 µg × mL-1) and Rhizopus stolonifer (500 µg × mL-1). Mycelial aggregation and structural changes such as excessive branching, swelling of the cell wall and hyphae size reduction were observed in the micrographs.637646Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Chitosan coatings in the maintenance of strawberry quality during refrigerated storage / Revestimentos de quitosana na manutenção da qualidade de morango durante o armazenamento refrigerado

 This study aimed to assess the use of chitosan coatings in the maintenance of postharvest quality of strawberries during refrigerated storage. The strawberries were selected, immersed in chitosan solution, packed and stored at 5°C for 20 days. The effect of different chitosan concentrations (0.5% and 1.0% w/v) on the qualitative aspects of the fruits was analyzed during storage. The parameters assessed were: weight loss, pH, titratable acidity, soluble solids, total sugars, reducing and non-reducing sugars and ascorbic acid. It was observed that refrigerated storage, associated with chitosan coatings, was effective in maintaining postharvest quality of strawberries, given that chitosan coatings delayed changes in weight loss, soluble solids, total sugars, reducing and non-reducing sugars, titratable acidity, ascorbic acid and pH during 20 days of storage. The chitosan concentration of 1.0% (w/v) was the most promising in maintaining quality, as well as preserving the fruits for more than 10 days under refrigeratio

Biosynthesis of Xanthan Gum from Fermenting Shrimp Shell: Yield and Apparent Viscosity

With the aim of producing xanthan gum, the effects of an aqueous shrimp shell extract (SSAE) as the source of carbon and nitrogen on the yield and apparent viscosity of the gums produced by fermentation using three native strains of Xanthomonas campestris were studied. It was found that the SSAE contained 89.75% moisture, 0.054% ash, 8.069% protein, 0.787 lipids, and 1.337% carbohydrates. Media containing different concentrations of SSAE and supplemented with urea (0.01%) and phosphate (0.1%) were fermented in a shaker, and the results obtained were compared with those obtained from sucrose (control) with the same supplementation and fermentation conditions. Strain 1182 showed the highest yield (4.64 g·L−1) and viscosity (48.53 mPa·s), from the medium containing 10% (w/v) of SSAE. These values were higher than those obtained from the control medium containing sucrose. Shrimp shell is a low cost residue that can be bioconverted into products of high added value such as xanthan gum

Alterações pós-colheita da "fruta-de-lobo" (Solanum lycocarpum St. Hil.) durante o amadurecimento: análises físico-químicas, químicas e enzimáticas

Estudaram-se, neste trabalho, algumas modificações físico-químicas, químicas e enzimáticas, em pós-colheita, durante o amadurecimento da fruta-de-lobo, comparando-as com as de outros frutos. Os frutos colhidos de plantas nativas no início do estádio de amadurecimento foram selecionados e armazenados durante 18 dias à temperatura ambiente (17,1 a 26,9ºC). Os frutos foram lavados com água destilada, descascados, picados, congelados em nitrogênio líquido e liofilizados até massa constante. O delineamento experimental utilizado foi o inteiramente casualizado, com quatro repetições de 3 frutos. Os valores de pH e acidez titulável não variaram estatisticamente durante o amadurecimento. A atividade de amilase e os teores de amido diminuíram gradativamente com o aumento dos açúcares solúveis totais e não redutores, enquanto os teores dos redutores se mantiveram constantes. Os teores de pectinas totais e solúveis diminuíram, enquanto a atividade de pectinametilesterase manteve-se constante. As atividades das enzimas poligalacturonase e polimetilgalacturonase não foram detectadas no fruto. Observou-se diminuição dos teores de polifenóis e das atividades das enzimas peroxidase e polifenoloxidase e conseqüente diminuição do escurecimento da polpa do fruto