Biorefinery with deep eutectic solvent (DES) is an emerging processing technology to overcome the shortcomings of conventional biomass pretreatments. This work evaluates the biorefinery of sugarcane bagasse (SCB) with DES formulated with choline chloride as hydrogen bond acceptor and three hydrogen bond donors: lactic acid, citric acid, and acetic acid. Acetic acid showed unique ionic properties responsible for the selective removal of lignin and the deconstruction of cellulose to improve the digestibility of up to 97.61 % of glucan and 63.95 % of xylan during enzymatic hydrolysis. In addition, the structural characteristics of the polysaccharide-rich material (PRM) were analyzed by X-rays, ATR-FTIR, SEM, and enzymatic hydrolysis, and compared with the original material sample, for a comprehensive understanding of biomass deconstruction using different hydrogen bond donors (HBD) as DES pretreatment.

The effect of chitosan on Saccharomyces cerevisiae (the yeast that carries out alcohol fermentation), Brettanomyces bruxellensis and Brettanomyces intermedius (contaminants of alcohol fermentations), was investigated. The effect of chitosan was tested on each yeast, as well as on mixed cultivations of S. cerevisiae + B. bruxellensis and S. cerevisiae + B. intermedius. Chitosan enhanced the lag period of both strains of Brettanomyces (80 h for B. bruxellensis and 170 h for B. intermedius with 6 and 2 g/l chitosan, respectively). The growth rate of S. cerevisiae was inversely proportional to the chitosan concentration; the former was 50% when 6 g/l polysaccharide was used. Moreover, in mixed cultivations of S. cerevisiae and Brettanomyces strains, it was found that both B. bruxellensis and B. intermedius failed to grow while growth of S. cerevisiae was not affected (using 3 and 6 g/l chitosan, respectively). An interesting collateral result was that the presence of chitosan accelerated the consumption of glucose in the mixed cultivations (60 h instead of 120 h).

A chitinolytic enzyme from Bacillus thuringiensis subsp. aizawai has been purified and its molecular mass was estimated ca. 66 kDa by sodium dodecyl sulfate – polyacryamide gel electrophoresis (SDS–PAGE). The enzyme was able to hydrolyze chitin to chitobiosides but not carboxymethylcellulose, cellulose, pullulan, and laminarin. Optimal pH and temperature were detected at 6 and 50 °C, respectively. Stability, in the absence of substrate, was observed at temperatures less than 60 °C and pH between 5 and 8. Enzyme activity was significantly inhibited by K⁺and EDTA and completely inhibited by Hg²⁺. Purified chitinase showed lytic activity against cell walls from six phytopathogenic fungi and inhibited the mycelial growth of both Fusarium sp. and Sclerotium rolfsii. The biocontrol efficacy of the enzyme was tested in the protection of bean seeds infested with six phytopathogenic fungi.Key words: chitinase, Bacillus thuringiensis, purification, phytopathogenic fungi.