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Lignin is an abundant biopolymer in nature; because of its polymeric structure, it is a potential source of aromatic compounds with high added value in the chemical, food and pharmaceutical industries. Lignin can be used with chemical and biological procedures that depolymerize it in a gradual and selective manner. Peroxidases and laccases are enzymes used as oxidizing agents in processes of oxidative depolymerization; however, the use of H2O2 as secondary electron acceptor to increase the oxidizing effect of immobilized laccase is not reported so far. The objective of this study was to evaluate the catalytic capacity of laccase (1.25 mUI) immobilized in alginate pearls, with a particle diameter (Dp) of 3 mm, in order to obtain aromatic compounds from lignin oxidation. The reactions were kept with agitation and controlled temperature, the pH varied and H2O2 was used as secondary electron acceptor. The experimental design was factorial 3 x 4: three pH values (5.8, 6.5 and 8.6) and four concentrations of H2O2 (25, 50, 75 and 100 mM); the trials were performed in triplicate. ANDEVA was carried out with the data as well as means comparison tests (Tukey, p≤0.05). The highest conversion of lignin to aromatic compounds was obtained with a pH of 8.6: benzoic acid (63.5 %), vanillic acid (25 %) and vanillin (11.5 %). The immobilizing support for the enzyme was disintegrated and dissolved in the medium in the reactions catalyzed with a pH over 7.0. The results allow suggesting that the degree of lignin depolymerization with immobilized laccase depends directly on the concentration of H2O2 and the medium's pH. [ABSTRACT FROM AUTHOR]

Fermentation technologies were developed to improve the production of ethanol and an alternative is the immobilization technology, which offers advantages in comparison with free cells culture, such as the possibility of efficiently incorporating symbiotic bacteria in the same matrix. The aim of this study was to evaluate, in equivalent medium, the use of mango (Mangifera indica) waste to produce ethanol. The study compared the production of ethanol by using Zymomonas mobilis and Saccharomyces cerevisiae in free cells culture, immobilized and coimmobilized in calcium alginate in a culture medium equivalent to mango juice. It also included an evaluation of the effect of glucose concentration on productivity in a coimmobilized system. The experimental design was triplicate cultures in a Chemostat reactor Ommi Culture Plus for S. cerevisiae and Z. mobilis in free cell culture, immobilized and coimmobilized. The results showed that in free cell culture, the productivity was higher for Z. mobilis (5.76 g L-1 h-1) than for S. cerevisiae (5.29 g L-1 h-1); in coimmobilized culture, a higher productivity was obtained (8.80 g L-1 h-1) with respect to S. cerevisiae and Z. mobilis immobilized (8.45 g L-1 h-1 and 8.70 g L-1 h-1). The conversion of glucose to ethanol was higher (6.91 mol ethanol) for culture with 50 g L-1 of glucose compared to 200 g L-1 of glucose (5.82 mol ethanol). Productivity values were higher in immobilized and coimmobilized cultures than in those with free cells, and represent an opportunity for the reuse of organic residues to alcohol production. [ABSTRACT FROM AUTHOR]