RESUMEN
This study aimed at isolating and characterizing of microorganisms able to use linamarin as sole carbon source. Thirty one microbial strains were isolated from manipueira, a liquid effluent of cassava processing factories. Among these strains, Bacillus licheniformis (isolate 2_2) and Rhodotorulla glutinis (isolate L1) were able to degrade 71 percent and 95 percent of added linamarin, respectively, within 7 days, showing high biodegradation activity and great potential for detoxification of cassava processing wastewaters.
Asunto(s)
Biodegradación Ambiental , Bacillus/aislamiento & purificación , Técnicas In Vitro , Linaceae , Manihot , Estructuras de las Plantas , Manipulación de Alimentos , Métodos , MétodosRESUMEN
This study aimed at isolating and characterizing of microorganisms able to use linamarin as sole carbon source. Thirty one microbial strains were isolated from manipueira, a liquid effluent of cassava processing factories. Among these strains, Bacillus licheniformis (isolate 2_2) and Rhodotorulla glutinis (isolate L1) were able to degrade 71% and 95% of added linamarin, respectively, within 7 days, showing high biodegradation activity and great potential for detoxification of cassava processing wastewaters.
RESUMEN
Cassava starches are widely used in the production of biodegradable films, but their resistance to humidity migration is very low. In this work, commercial cassava starch films were studied and classified according to their physicochemical properties. A nondestructive method for water vapor permeability determination, which combines with infrared spectroscopy and multivariate calibration, is also presented. The following commercial cassava starches were studied: pregelatinized (amidomax 3550), carboxymethylated starch (CMA) of low and high viscosities, and esterified starches. To make the films, 2 different starch concentrations were evaluated, consisting of water suspensions with 3% and 5% starch. The filmogenic solutions were dried and characterized for their thickness, grammage, water vapor permeability, water activity, tensile strength (deformation force), water solubility, and puncture strength (deformation). The minimum thicknesses were 0.5 to 0.6 mm in pregelatinized starch films. The results were treated by means of the following chemometric methods: principal component analysis (PCA) and partial least squares (PLS) regression. PCA analysis on the physicochemical properties of the films showed that the differences in concentration of the dried material (3% and 5% starch) and also in the type of starch modification were mainly related to the following properties: permeability, solubility, and thickness. IR spectra collected in the region of 4000 to 600 cm(-1) were used to build a PLS model with good predictive power for water vapor permeability determination, with mean relative errors of 10.0% for cross-validation and 7.8% for the prediction set.
Asunto(s)
Química Física/métodos , Manihot/química , Espectroscopía Infrarroja por Transformada de Fourier/métodos , Almidón/química , Agua , Calibración , Fuerza Compresiva , Embalaje de Alimentos , Análisis de los Mínimos Cuadrados , Permeabilidad , Valor Predictivo de las Pruebas , Análisis de Componente Principal , Reproducibilidad de los Resultados , Solubilidad , Propiedades de Superficie , Resistencia a la Tracción , VolatilizaciónRESUMEN
Cassava is a widely grown root crop which accumulates two cyanogenic glucosides, linamarin and lotaustralin. Linamarin accounts for more than 80 per cent of the cassava cyanogenic glucosides. It is a beta-glucoside of acetone cyanohydrin and ethyl-methyl-ketone-cyanohydrin. Linamarin beta-linkage can only be broken under high pressure, high temperature and use of mineral acids, while its enzymatic break occurs easily. Linamarase, an endogenous cassava enzyme, can break this beta-linkage. The enzymatic reaction occurs under optimum conditions at 25ºC, at pH 5.5 to 6.0. Linamarin is present in all parts of the cassava plant, being more concentrated on the root and leaves. If the enzyme and substrate are joined, a good detoxification can occur. All the cassava plant species are known to contain cyanide. Toxicity caused by free cyanide (CN-) has already been reported, while toxicity caused by glucoside has not. The lethal dose of CN- is 1 mg/kg of live weight; hence, cassava root classification into toxic and non-toxic depending on the amount of cyanide in the root. Should the cyanide content be high enough to exceed such a dose, the root is regarded as toxic. Values from 15 to 400 ppm (mg CN- of fresh weight) of hydrocyanic acid in cassava roots have been mentioned in the literature. However, more frequent values in the interval 30 to 150 ppm have been observed. Processed cassava food consumed in Brazil is safe in regard to cyanide toxicity.