Thayza Christina Montenegro Stamford

Physico-chemical characteristics and functional properties of chitin and chitosan produced by Mucor circinelloides using yam bean as substrate.

Microbiological processes were used for chitin and chitosan production by Mucor circinelloides (UCP 050) grown in yam bean (Pachyrhizus erosus L. Urban) medium. The polysaccharides were extracted by alkali–acid treatment and structural investigations by X-ray diffraction, Fourier transform IR analysis, viscosity and thermal analysis by TG, DTG, and DTA were done. The highest biomass yield (20.7 g/L) was obtained at 96 hours. The highest levels of chitosan (64 mg/g) and chitin (500 mg/g) were produced at 48 and 72 hours, respectively. It was demonstrated that yam bean shows great potential as an economic medium and it is possible to achieve a good yield of chitosan with chemical properties that enable its use in biotechnological applications.

Action of silver nanoparticles towards biological systems: cytotoxicity evaluation using hen's egg test and inhibition of Streptococcus mutans biofilm formation

This study aimed to evaluate the cytotoxicity and bactericidal properties of four silver nanoparticle (AgNP) colloids and their ability to inhibit Streptococcus mutans biofilm formation on dental enamel. The cytotoxicity of AgNPs was evaluated based on signs of vascular change on the chorioallantoic membrane using the hens egg test (HET-CAM). Bactericidal properties and inhibition of S. mutans biofilm formation were determined using a parallel-flow cell system and a dichromatic fluorescent stain. The percentage of viable cells was calculated from regression data generated from a viability standard. AgNP colloids proved to be non-irritating, as they were unable to promote vasoconstriction, haemorrhage or coagulation. AgNP colloids inhibited S. mutans biofilm formation on dental enamel, and cell viability measured by fluorescence was 0% for samples S1, S2, S3 and S4 and 36.5% for the positive control (diluted 30% silver diamine fluoride). AgNPs are new products with a low production cost because they have a lower concentration of silver, with low toxicity and an effective bactericidal effect against a cariogenic oral bacterium. Moreover, they do not promote colour change in dental enamel, which is an aesthetic advantage compared with traditional silver products.

Antimicrobial and cytotoxicity evaluation of colloidal chitosan – silver nanoparticles – fluoride nanocomposites

The present study aimed to evaluate the antimicrobial activity and cytotoxicity of colloidal chitosan - silver nanoparticle - fluoride nanocomposites (CChAgNpFNc), with different silver nanoparticle shapes and sizes. The syntheses of CChAgNpFNc were performed with silver nitrate added to a chitosan solution, addition of a sodium borohydride solution and solid sodium fluoride. Solution of ascorbic acid was added to synthesize larger silver nanoparticles. CChAgNpFNc obtained: S1- 100% spherical, 8.7±3.1nm; S2- 97% spherical, 15.0±7.9nm and 2.5% triangular, 22.2±9.5nm; S3- 77.3% spherical, 31.8±10.4nm, 15.9% triangular, 27.1±10.1nm and 6.8% elliptical, 33.2±7.8nm; and S4- 75.2% spherical, 43.2±14.3nm; 23.3% triangular 38.2±14.8nm, and 1.5% elliptical 38.4±11.6nm. The CChAgNpFNc showed antimicrobial activity against Staphylococcus aureus, Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa and Candida albicans, by microdilution technique. The influence on the growth of microorganisms was evaluated using a fluorescence assay, and showed an increasing lag phase and a decreasing log phase. Cytotoxicity was investigated using Artemia salina and MTT assays. The S3 and S4 samples exhibited low cytotoxicity. The S1 and S2 samples inhibited murine macrophages and revealed lethal dose concentrations above 1000mg/mL that were classified as moderately toxic. Thus, CChAgNpFNc are potential options for the control of multiple-drug-resistant microorganisms and do not represent substantial risks to human health.

Green Conversion of Agroindustrial Wastes into Chitin and Chitosan by Rhizopus arrhizus and Cunninghamella elegans Strains

This article sets out a method for producing chitin and chitosan by Cunninghamella elegans and Rhizopus arrhizus strains using a green metabolic conversion of agroindustrial wastes (corn steep liquor and molasses). The physicochemical characteristics of the biopolymers and antimicrobial activity are described. Chitin and chitosan were extracted by alkali-acid treatment, and characterized by infrared spectroscopy, viscosity and X-ray diffraction. The effectiveness of chitosan from C. elegans and R. arrhizus in inhibiting the growth of Listeria monocytogenes, Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella enterica, Escherichia coli and Yersinia enterocolitica were evaluated by determining the minimum inhibitory concentrations (MIC) and the minimum bactericidal concentrations (MBC). The highest production of biomass (24.60 g/L), chitin (83.20 mg/g) and chitosan (49.31 mg/g) was obtained by R. arrhizus. Chitin and chitosan from both fungi showed a similar degree of deacetylation, respectively of 25% and 82%, crystallinity indices of 33.80% and 32.80% for chitin, and 20.30% and 17.80% for chitosan. Both chitin and chitosan presented similar viscosimetry of 3.79–3.40 cP and low molecular weight of 5.08 × 103 and 4.68 × 103 g/mol. They both showed identical MIC and MBC for all bacteria assayed. These results suggest that: agricultural wastes can be produced in an environmentally friendly way; chitin and chitosan can be produced economically; and that chitosan has antimicrobial potential against pathogenic bacteria.

Efficacy of a coating composed of chitosan from Mucor circinelloides and carvacrol to control Aspergillus flavus and the quality of cherry tomato fruits

Cherry tomato (Lycopersicon esculentum Mill) fruits are susceptible to contamination by Aspergillus flavus, which may cause the development of fruit rot and significant postharvest losses. Currently there are significant drawbacks for the use of synthetic fungicides to control pathogenic fungi in tomato fruits, and it has increased the interest in exploring new alternatives to control the occurrence of fungal infections in these fruits. This study evaluated the efficacy of chitosan (CHI) from Mucor circinelloides in combination with carvacrol (CAR) in inhibiting A. flavus in laboratory media and as a coating on cherry tomato fruits (25°C, 12 days and 12°C, 24 days). During a period of storage, the effect of coatings composed of CHI and CAR on autochthonous microflora, as well as on some quality characteristics of the fruits such as weight loss, color, firmness, soluble solids, and titratable acidity was evaluated. CHI and CAR displayed MIC valuesof 7.5 mg/mL and 10 μL/mL, respectively, against A. flavus. The combined application of CHI (7.5 or 3.75 mg/mL) and CAR (5 or 2.5 μL/mL) strongly inhibited the mycelial growth and spore germination of A. flavus. The coating composed of CHI (3.75 mg/mL) and CAR (2.5 or 1.25 μL/mL) inhibited the growth of A. flavus in artificially contaminated fruits, as well as the native fungal microflora of the fruits stored at room or low temperature. The application of the tested coatings preserved the quality of cherry tomato fruits as measured by some physicochemical attributes. From this, composite coatings containing CHI and CAR offer a promising alternative to control postharvest infection caused by A. flavus or native fungal microflora in fresh cherry tomato fruits without negatively affecting their quality over storage.

Effect of Corn Steep Liquor (CSL) and Cassava Wastewater (CW) on Chitin and Chitosan Production by Cunninghamella elegans and Their Physicochemical Characteristics and Cytotoxicity

Microbiological processes were used for chitin and chitosan production with Cunninghamella elegans UCP/WFCC 0542 grown in different concentrations of two agro-industrial wastes, corn steep liquor (CSL) and cassava wastewater (CW) established using a 22 full factorial design. The polysaccharides were extracted by alkali-acid treatment and characterized by infrared spectroscopy, viscosity, thermal analysis, elemental analysis, scanning electron microscopy and X-ray diffraction. The cytotoxicity of chitosan was evaluated for signs of vascular change on the chorioallantoic membrane of chicken eggs. The highest biomass (9.93 g/L) was obtained in trial 3 (5% CW, 8% CSL), the greatest chitin and chitosan yields were 89.39 mg/g and 57.82 mg/g, respectively, and both were obtained in trial 2 (10% CW, 4% CSL). Chitin and chitosan showed a degree of deacetylation of 40.98% and 88.24%, and a crystalline index of 35.80% and 23.82%, respectively, and chitosan showed low molecular weight (LMW 5.2 × 103 Da). Chitin and chitosan can be considered non-irritating, due to the fact they do not promote vascular change. It was demonstrated that CSL and CW are effective renewable agroindustrial alternative substrates for the production of chitin and chitosan.

Effects of Dietary Brazilian Palm Oil (Mauritia flexuosa L.) on Cholesterol Profile and Vitamin A and E Status of Rats

In vitro studies have been carried out to establish the nutritional differences between crude and refined vegetable oils; however, the impact of the consumption of these foods on metabolism, in particular the effect of buriti oil, needs to be further evaluated. The aim of this study was to evaluate the biochemical and murine parameters and the vitamin A and E status in young rats fed with diets supplemented with crude or refined buriti oil. The animals (n = 30) were randomized into three groups receiving diet added of soybean oil (control), crude buriti oil (CBO) and refined buriti oil (RBO) for 28 days. Rats fed with diet added of refined buriti oil (RBO) showed reduced total cholesterol (up to 60.27%), LDL (64.75%), triglycerides (55.47%) and enzyme aspartate transaminase (21.57%) compared to those fed with diet added of crude oil. Serum and hepatic retinol and tocopherol were higher by two to three times in CBO and RBO groups compared to the control group, but no differences were observed for murine parameters. The results indicate that buriti oil is an important source of the antioxidant vitamins A and E, and refined buriti oil is suggested as alternative to improve the lipid profile of healthy rats.

Microbiological Chitosan: Potential Application as Anticariogenic Agent

Dental caries is the most prevalent oral disease that affects a significant part of the world population, especially in less developed countries. It is universally accepted that the dental caries is a chronic and multifactorial disease [1-3]. The permanence of the bacterial plaque on the tooth surface will lead to loss of minerals constituents of the dental enamel promoting the installation of the carie disease. The carious lesion is characterized by the tooth structure (hydroxyapatite) demineralization by the production of organic acids, such as lactic acid, resulting from bacterial (dental biofilm) metabolism. This results in loss of calcium and phosphate ions which subsequently diffuse out of the tooth. In this complex process, the microorganisms, particularly Streptococcus species, have an important role in its etiology [3-5].

Parâmetros bioquímicos e microbiológicos e suas relações com a experiência de cárie em adolescentes sadios

OBJECTIVES: to establish a relationship between dental caries with the degree of Streptococcus mutans present in the salivary flow and saliva buffer ability in 111 healthy adolescents seen at the Pediatrics Outpatient Clinic of the Hospital das Clinicas de Pernambuco. METHODS: Intraoral examinations were performed and dental records filled to determine DMFS-S (Decayed, missing teeth and filled permanent dental surfaces). Following, saliva was collected to determined salivary flow and buffer ability. Front teeth were scrapped to quantify Streptococcus mutans present in the bacterial plaque. RESULTS: the population assessed had predominantly low caries activities with buffer ability of normal saliva and deficiency of salivary flow. The numbers of S mutans in the bacterial plaque exceeded 105 CFU/mg in the majority of individuals in the population studied. CONCLUSIONS: caries activity was inversely proportional to the buffer capacity and directly proportional to the presence of Streptococus mutans in the bacterial plaque. This low carie activity could be derived from the daily tooth-brushing with fluor dentifrices.

Formulation of mayonnaise with the addition of a bioemulsifier isolated from Candida utilis

Graphical abstract