Beáta Ábrahám

A possible explanation of the germicide effect of carbon dioxide in supercritical state based on molecular-biological evidence

Supercritical carbon dioxide (CO(2)) possesses germicide (bactericide and sporicide) effect. Despite of the fact, that this effect is used in industrial sterilization processes, the sterilization mechanism at molecular level is unclear. Our hypotheses can provide a molecular-biological explanation for the phenomenon. We believe that in supercritical state CO(2) reacts competitively with Met-tRNA(fMet), the formation rate and the amount of formyl-methionyl-tRNA (fMet-tRNA(fMet)) will be diminished by irreversible substrate consumption. The fMet-tRNA(fMet) possesses a key role in prokaryotic protein synthesis, being almost exclusively the initiator aminoacyl-tRNA. The formed carbamoyl-methionyl-tRNA (cMet-tRNA(fMet)), probably stable only under pressure and high CO(2) concentration, is stabilized by forming a ternary molecular complex with the GTP-form of the translational initiation factor 2 (GTP-IF2). This complex is unable to dissociate from preinitiation 70S ribosomal complex because of strong polar binding between the protein C-2 domain and the modified initiator aminoacyl-tRNA. The IF2-fMet-tRNA(fMet)-blocked 70S ribosomal preinitiation complex does not decompose following the GTP hydrolysis, becoming unable to synthesize proteins. The death of the microbial cell is caused by inhibition of the protein synthesis and energetic depletion. Moreover, we propose a possible mechanism for the accumulation of cMet-tRNA(fMet) in the bacterial cell. Since the translational process is an important target for antibiotics, the proposed mechanism could be a work hypothesis for discovery of new antibiotics. Made by high conservative character of prokaryotic translation initiation, the proposed IF2 pathway deterioration strategy may conduct to obtaining selective (with low mammalian toxicity) antimicrobials and at the same time, with reduced possibility of the drug resistance development.

Cultivating conditions optimization of the anaerobic digestion of corn ethanol distillery residuals using response surface methodology

This study investigated the individual and interactive effects of three factors — temperature, inoculum/substrate ratio (ISR) and inoculum typology — on the anaerobic digestion of corn ethanol distillery wastewater. Biochemical methane potential assays planned with factorial design with two independent quantitative variables on three levels (ISR: 1:1, 2:1 and 3:1; temperature: 30°C, 33.5°C, 37°C) and one independent qualitative variable (inoculum type: suspended, granular, mixed) have been performed. Response Surface Methodology has been used to study the effect of the factors with the aim of maximizing the specific methane yields (YCH4) obtainable with this substrate. The results show that all three investigated factors influence in a significant matter the YCH4, the ISR having the strongest effect on it. The temperature has significant influence on the YCH4 only in combination with high ISR values. The optimal conditions for the maximum YCH4 (551 mL CH4 g−1 VSadded) have been found at 37°C operating temperature, ISR=3:1 and using granular inoculum. These conditions gave rise to a 4-fold increase of YCH4 with respect to the worst combination of factors (YCH4=129 mL g−1 VSadded for the suspended inoculum type, at 30°C and ISR=1:1). The results improve the knowledge on the digestion of this substrate, providing information for successful process up-scaling.

Bacterial Strains with Nutrient Mobilisation Ability from Ciuc Mountains (Transylvania Region, Romania)

This chapter presents the study about some wild leguminous plant’s nodule and rhizosphere bacteria from Ciuc Mountains with beneficial traits related to mineral nutrition and their multiple plant growth-promoting activities as a part of plant-bacteria interaction.

Preparation and Investigation of Bioactive Transferrin-Iron Complexes Formed with Different Synergistic Anions

Human serum transferrin has a potential for drug-delivery systems. Oxalate and aziridine-carboxylate was conjugated to serum transferrin in order to transport into the targeted cancer cells via transferrin-receptor mediated endocytosis. Capillary zone electrophoresis and capillary isoelectric focusing were used to analyze the effectiveness of complexation reactions. The electropherograms show the differences between iron-free- and iron-complexed molecular forms of human serum transferrin. The iron-complexed transferrin sample containing the different anions as synergistic complexing agents were characterized by different electrophoretic parameters.