High-pressure anaerobic digestion up to 100†bar: influence of initial pressure on production kinetics and specific methane yields.

To ensure an efficient use of biogas produced by anaerobic digestion, in some cases it would be advisable to upgrade the biogenic gases and inject them into the transnational gas grids. To investigate biogas production under high-pressure conditions up to 100 bar, new pressure batch methane reactors were developed for preliminary lab-scale experiments with a mixture of grass and maize silage hydrolysate. During this investigation, the effects of different initial pressures (1, 50 and 100 bar) on pressure increase, gas production and the specific methane yield using nitrogen as inert gas were determined. Based on the experimental findings increasing initial pressures alter neither significantly, further pressure increases nor pressure increase rates. All supplied organic acids were degraded and no measurable inhibition of the microorganisms was observed. The results show that methane reactors can be operated at operating pressures up to 100 bar without any negative effects on methane production.

Influence of pressures up to 50bar on two-stage anaerobic digestion.

The concept of pressurized two-stage anaerobic digestion integrates biogas production, purification and pressure boosting within one process. The produced methane-rich biogas can be fed into gas grids with considerably less purification effort. To investigate biogas production under high pressures up to 50bar, a lab scale two-stage anaerobic digestion system was constructed including one continuously operated pressurized methane reactor. This investigation examined the effects of different operating pressures in methane reactor (10, 25, 50bar) on biogas quantity and quality, pH value and process stability. By increasing operating pressures in methane reactor, the pH value decreased from 6.65 at 10bar to 6.55 at 50bar. Simultaneously, methane content increased from 79.08% at 10bar to 90.45% at 50bar. The results show that methane reactors can be operated up to 50bar pressure continuously representing a viable alternative to commonly used gas upgrading methods because of reduced purification effort.

MicroRNA-146: tiny player in neonatal innate immunity?

BACKGROUND: Concise regulation of the Toll signaling pathway is mandatory in neonatal innate immunity. The microRNA-146 family (miR-146a/b) was recently reported to be a regulator of Toll-like receptor 4 (TLR4) through a negative feedback loop mechanism. Acting as a potent regulator, miRNA helps to protect the organism from developing overwhelming proinflammatory immune responses leading to septic shock or chronic inflammatory diseases. OBJECTIVE: We investigated for the first time whether miRNA-146a/b plays a regulatory role in human monocytes derived from infant cord or adult blood, and whether differences in miRNA-146 expression exist. METHODS: Expression profiles of miR-146a/b and TLR4 were studied by real-time PCR upon stimulation with lipopolysaccharide. RESULTS: Both members of the miRNA-146 family showed a time-dependent upregulation. For miR-146a, a statistically higher significant increase was found after 24 h of stimulation in monocytes from cord blood compared to those derived from adults. In contrast, no differences were found for miR-146b and TLR4, respectively. CONCLUSION: We conclude that differences between the negative regulatory role for miR-146a obviously exist in neonatal and adult TLR4 signaling, and suggest that more intense research in the involvement of miRNA in immune regulation will facilitate the understanding of the development and function of the innate immune system of neonates.