Antimicrobial activity and chemical profile of wood vinegar from eucalyptus (Eucalyptus urophylla x Eucalyptus grandis - clone I144) and bamboo (Bambusa vulgaris).

Microbial resistance to drugs is a public health problem; therefore, there is a search for alternatives to replace conventional products with natural agents. One of the potential antimicrobial agents is wood vinegar derived from the carbonization of lignocellulosic raw materials. The objectives of the present work were to evaluate the antibacterial and antifungal action of two kinds of wood vinegar (WV), one of Eucalyptus urograndis wood and another of Bambusa vulgaris biomass, and determine their chemical profile. The antimicrobial effect was assessed against Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella enteritidis, Escherichia coli, Streptococcus agalactiae, and Candida albicans. The minimum inhibitory concentration and the minimum bactericidal and fungicidal concentrations were determined. Micrographs of the microorganisms before and after exposure to both kinds of wood vinegar were obtained by scanning electron microscopy. The chemical profile of the eucalyptus and bamboo vinegar was carried out by gas chromatography and mass spectrometry (GC/MS). Both types of WV presented significant antimicrobial activity, with the bamboo one having a higher efficiency. Both studied pyroligneous extracts seem promising for developing natural antimicrobials due to their efficiency against pathogens. GC/MS analyses demonstrated that the chemical profiles of both kinds of WV were similar but with some significant differences. The major component of the eucalyptus vinegar was furfural (17.2%), while the bamboo WV was phenol (15.3%). Several compounds in both WVs have proven antimicrobial activity, such as acetic acid, furfural, phenol, cresols, guaiacol, and xylenols. Together, they are the major in the chemical composition of the organic fraction of both WVs. Bamboo vinegar had a more expressive content of organic acids. Micrographs of microorganisms taken after exposure to both kinds of wood vinegar displayed several cell modifications. The potential of both types of wood vinegar as a basis for natural antimicrobial products seems feasible due to their proven effect on inhibiting the microorganisms' growth assessed in this experiment.

Briquette production as a sustainable alternative for waste management in the tannin extraction industry.

Tannins are polyphenols that can be extracted from different parts of the plant and have different known commercial applications. The extraction of tannins generates a significant amount of low-density wastes. An alternative that can be applied to ensure energy reuse of this low-density waste is a densification process, such as briquetting. Thus, this research work aimed to assess the energy potential of the residue from the extraction of tannins of different forest species, aiming at its energy reuse in the form of briquettes. Stem barks of 6 forest species (Acacia mangium, AM; Anacardium occidentale, AO; Anadenanthera colubrina, AC; Azadirachta indica, AI; Mimosa caesalpiniaefolia, MC; Mimosa tenuiflora, MT) were used after tannin extraction. Bulk density, energy (higher, lower, and net heating value) and thermal (TG/DTG) properties, and chemical constitution (extractives, lignin, and holocellulose) of the materials were determined. In addition, briquette compaction ratio, apparent density, volumetric expansion, and water adsorption over the days were evaluated. The highest bulk densities were found in the barks of Anadenanthera colubrina (0.529 g.cm-3) and Mimosa tenuiflora (0.407 g.cm-3), whereas the species that showed the best result of higher heating value was Acacia mangium (20.44 MJ.kg-1), followed by Azadirachta indica (19.39 MJ.kg-1) and Mimosa caesalpiniifolia (18.85 MJ.kg-1). Briquetting increased the density of the evaluated material by 2.3 to 4.9 times. All briquettes produced with wastes from tannin extraction evaluated in this work showed potential for energy production. With more information on the quantification of waste generated and data on the economic viability of production, these tannin-producing industries can benefit both environmentally and economically, by reusing these wastes for energy production.