Banana starch was oxidized at three different levels and afterwards acetylated. The double-modified starch was used for film preparation with the addition of chitosan. The physical, mechanical, and barrier properties were tested. The oxidation level increased the moisture content of the film, but the acetylation and the addition of chitosan decreased this characteristic. The oxidation level increased the whiteness of the film, but the second modification (acetylation) and the addition of chitosan to the blend did not affect this parameter. The solubility increased with the temperature and the oxidation level but decreased with the storage time of the film. The oxidation increased and the acetylation reduced the solubility with respect to the native starch film. The dual modification produced a solubility value less than that of its oxidized counterpart, and the addition of chitosan produced the highest solubility value. The addition of chitosan increased the tensile strength of the film, and the effect was higher with the oxidation level and longest storage time. The addition of chitosan produced a higher elongation value than that of its double-modified film, but at the longest storage time, this parameter decreased. The water vapor permeability increased with the oxidation level because of the hydrophilic character, but the acetylation reduced this parameter because the acetylation increased the hydrophobic character of the starch due to the ester group. Films prepared with the double-modified banana starch and the addition of chitosan had some improved physical, mechanical, and barrier properties, and they may be used in specific applications.

Banana starch was oxidized at three different levels and then acetylated. The double-modified starch was used for film preparation. The physical, mechanical, and barrier properties were tested. The oxidation level increased the whiteness of the film, and the second modification (acetylation) did not affect this parameter. The solubility increased with temperature and oxidation level. However, acetylation decreased the solubility value. At the longest storage times, the solubility decreased because of starch reorganization inside the polymeric matrix. In general, oxidation increased the tensile strength of the films, and a slight increase was observed when the oxidized starch was acetylated. This effect was more noticeable at the longest storage time. The oxidation level decreased the percentage elongation at break, and a slight effect due to acetylation was observed. The film of oxidized-acetylated starch showed a higher elastic modulus

This work reports the study of chitosan depolymerization through the synergy of the Celuzyme® XB enzyme complex; it is composed of cellulase, xylanase, and β-glucanase. The optimal conditions of temperature, pH, and concentration were determined to verify the depolymerization reaction. The specificity of the enzymes at the β (1-4) glycosidic link site was checked. Low molecular weight chitosan (64 × 103 g·mol−1) with degree of acetylation 15% was obtained. The depolymerized chitosan products were characterized by infrared spectroscopy, the degree of acetylation was obtained by UV-Vis spectroscopy, and the determination of the molecular weight was obtained by capillary viscosimetry. With the depolymerized chitosan, membranes were formed and their antioxidant and antimicrobial functionality was determined; results show that these properties are dependent on the molecular weight and on the acetylation degree of chitosan.

Modelado de la biodegradación en biorreactores de lodos de hidrocarburos totales del petróleo intemperizados en suelos y sedimentos (Biodegradation modeling of sludge bioreactors of total petroleum hydrocarbons weathering in soil and sediments)

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