Germán Aroca

Biofiltration of high concentration of hydrogen sulphide using Thiobacillus thioparus

A biofiltration system using peat as solid support inoculated with Thiobacillus thioparus (ATCC 23645) was developed for treating a gaseous stream containing high concentrations of H2S. The inoculation systems allowed an efficient colonisation of the peat with T. thioparus, reaching 2.7×108 cells g−1 of dry peat. The biofilter reached an efficiency of 100% when fed with 355 ppm H2S and an air flow of 0.030 m3 h−1. When increasing the inlet concentration of the acid, the removal efficiencies of H2S decreased, reaching 90 and 60%, at 0.070 and 0.030 m3 h−1, respectively. A maximum value for the elimination capacities of 55 g m−3 h−1 was obtained. Mathematical modelling based on Ottengrafs model enabled a prediction of the performance of the biofilter.

Ethanol production improvement driven by genome-scale metabolic modeling and sensitivity analysis in Scheffersomyces stipitis

The yeast Scheffersomyces stipitis naturally produces ethanol from xylose, however reaching high ethanol yields is strongly dependent on aeration conditions. It has been reported that changes in the availability of NAD(H/+) cofactors can improve fermentation in some microorganisms. In this work genome-scale metabolic modeling and phenotypic phase plane analysis were used to characterize metabolic response on a range of uptake rates. Sensitivity analysis was used to assess the effect of ARC on ethanol production indicating that modifying ARC by inhibiting the respiratory chain ethanol production can be improved. It was shown experimentally in batch culture using Rotenone as an inhibitor of the mitochondrial NADH dehydrogenase complex I (CINADH), increasing ethanol yield by 18%. Furthermore, trajectories for uptakes rates, specific productivity and specific growth rate were determined by modeling the batch culture, to calculate ARC associated to the addition of CINADH inhibitor. Results showed that the increment in ethanol production via respiratory inhibition is due to excess in ARC, which generates an increase in ethanol production. Thus ethanol production improvement could be predicted by a change in ARC.

Actividad inhibitoria del sobrenadante de la bacteria Antártica Pseudomonas sp. M19B en la formación de biopelículas de Flavobacterium psychrophilum 19749

Flavobacterium psyhrophilum affects farmed salmon and trout worldwide and is the etiological agent of bacterial cold water disease. The treatment of this disease is made with antibiotics. The emergence of resistant strains and its ability to form biofilms have increased the resistance to antibiotics. Considering the diverse bioactivity of Antarctic bacteria, we evaluated the inhibitory effect of compounds secreted by Antarctic bacterial strains on the biofilm formation of F. psychrophilum 19749. 26.9% of the Antarctic bacterial isolates inhibited strongly the biofilm, the greatest effect was shown by M19B. Proteins (48-56 kDa) secreted by M19B may be related to the inhibition of the biofilm formation of F. psychrophilum 19749.