Cynthia Sequeiros

Hexavalent chromium removal in contaminated water using reticulated chitosan micro/nanoparticles from seafood processing wastes

Chitosan particles (CH) were obtained from seafood processing wastes (shrimp shells) and physicochemically characterized; deacetylation degree of CH was measured by Infrared Spectroscopy (FTIR) and potentiometric titration; polymer molecular weight was determined by intrinsic viscosity measurements. Reticulated micro/nanoparticles of chitosan (MCH) with an average diameter close to 100nm were synthesized by ionic gelation of chitosan using tripolyphosphate (TPP), and characterized by SEM, size distribution and Zeta-potential. Detoxification capacities of CH and MCH were tested analyzing the removal of hexavalent chromium Cr(VI) from contaminated water, at different initial chromium concentrations. The effect of pH on adsorption capacity of CH and MCH was experimentally determined and analyzed considering the Cr(VI) stable complexes (anions) formed, the presence of protonated groups in chitosan particles and the addition of the reticulating agent (TPP). Chitosan crosslinking was necessary to adsorb Cr(VI) at pH<2 due to the instability of CH particles in acid media. Langmuir isotherm described better than Freundlich and Temkin equations the equilibrium adsorption data. Pseudo-second order rate provided the best fitting to the kinetic data in comparison to pseudo-first order and Elovich equations. Chemical analysis to determine the oxidation state of the adsorbed Cr, showed that Cr(VI) was adsorbed on CH particles without further reduction; in contrast Cr(VI) removed from the solution was reduced and bound to the MCH as Cr(III). The reduction of toxic Cr(VI) to the less or nontoxic Cr(III) by the reticulated chitosan micro/nanoparticles can be considered a very efficient detoxification technique for the treatment of Cr(VI) contaminated water.

Newly isolated Bacillus sp. G51 from Patagonian wool produces an enzyme combination suitable for felt-resist treatments of organic wool

Bacteria from Patagonian Merino wool were isolated to assess their wool-keratinolytic activity and potential for felt-resist treatments. Strains from Bacillus, Exiguobacterium, Deinococcus, and Micrococcus produced wool-degrading enzymes. Bacillus sp. G51 showed the highest wool-keratinolytic activity. LC-MS/MS analysis revealed that G51 secreted two serine proteases belonging to the peptidase family S8 (MEROPS) and a metalloprotease associated with Bacillolysin, along with other enzymes (γ-glutamyltranspeptidase and dihydrolipoyl dehydrogenases) that could be involved in reduction of keratin disulfide bonds. Optimum pH and temperature of G51 proteolytic activity were 9 and 60 °C, respectively. More than 80% of activity was retained in H2O2, Triton X-100, Tween 20, Lipocol OXO650, Teridol B, and β-mercaptoethanol. Treatment of wool top with G51 enzyme extract caused a decrease in wool felting tendency without significant weight loss (<1.5%). Sparse work has so far been performed to investigate suitable keratinases for the organic wool sector. This eco-friendly treatment based on a new enzyme combination produced by a wild bacterium has potential for meeting the demands of organic wool processing which bans the use of hazardous chemicals and genetic engineering.

Chitosan from Marine Crustaceans: Production, Characterization and Applications

Chitosan is a very useful marine polysaccharide that forms structural components in the exoskeleton of crustaceans. In this chapter, the production of chitosan (CH) and chitosan reticulated micro/nanoparticles (CHM) is described. Three case studies corresponding to different effective applications of chitosan are discussed: (i) the performance of CH to destabilize oil/water emulsion waste for water clarification. It was observed that as long as colloidal charge was maintained around zero, turbidity also showed low values and water clarification was achieved. However, when the applied doses were higher than the optimum, colloidal charge and turbidity both increased, showing emulsion restabilization. Emulsions treated with the optimum chitosan doses were clarified in very short periods; (ii) CH and CHM were used as effective antibacterial agents against three different pathogenic microorganisms that are problematic for aquaculture: Vibrio alginolyticus and parahaemolyticus, and Lactococcus garvieae and the minimum bactericidal concentrations were determined; and (iii) the removal of hexavalent chromium and the comparative performance of CH versus CHM. Results showed that at pH < 2, the adsorption capacity of CHM was higher because CH is unstable. Additionally, Cr(VI) was adsorbed on CH without further reduction; in contrast, Cr(VI) adsorbed on CHM was reduced to nontoxic Cr(III).

Alkaline Proteases from Patagonian Bacteria

In addition to their ecological importance in the acquisition of nitrogen-rich organic compounds, extracellular proteases also have interesting biotechnological applications. Particularly, alkaline proteases represent one of the most important groups of commercial enzymes. First, we introduce the classification and catalytic mechanisms of proteases. Then, this chapter reviews the advances in the bioprospection of alkaline proteases produced by bacteria adapted to selective conditions from different environments of Patagonia (Argentina). Among them, the arid soils of the Patagonian Monte are propitious for the development of alkaliphilic microorganisms. Thus, we focus on the description of the species Bacillus patagoniensis and the biochemical and catalytic properties of its alkaline protease. Then, we discuss investigations about alkaline protease-producing bacteria from the southern Patagonian coast, the prevalence of psychrophilic and psychrotolerant strains, and the response of their extracellular proteases to temperature.

Microorganisms from Patagonian Aquatic Environments for Use in Aquaculture

Argentinean Patagonia is an extensive area scarcely explored from the microbiological point of view. Pristine and cold aquatic Patagonian environments as well as their fauna harbor a microbial diversity with interesting characteristics for application in aquaculture. This chapter presents the importance of aquaculture in recent decades and the problems associated with its fast and intensive development. We focus on Patagonian microorganisms and their products with potential application in aquaculture either as probiotics or as a source of specific nutritional components (i.e., astaxanthin). Thus, we analyze the probiotic characteristics of different bacteria from marine and freshwater environments. We also pay particular attention to antimicrobial agent production (i.e., bacteriocins) and adhesion properties of such strains. Moreover, we introduce Patagonian native yeasts as a promising natural source of astaxanthin and other valuable compounds for fish and crustacean aquaculture.