DECHEMA

About: DECHEMA is a nonprofit organization based out in Frankfurt am Main, Germany. It is known for research contribution in the topics: Corrosion & Oxide. The organization has 756 authors who have published 1307 publications receiving 25693 citations.

A continuous single organic phase process for the lipase catalyzed synthesis of peroxy acids increases productivity

Abstract: The design of an optimal process is particularly crucial when the reactants deactivate the biocatalyst. The reaction cascades of the chemo-enzymatic epoxidation where the intermediate peroxy acid is produced by an enzyme are still limited by enzyme inhibition and deactivation by hydrogen peroxide. To avoid additional effects caused by interfaces (aq/org) and to reduce the process limiting deactivation by the substrate hydrogen peroxide, a single-phase concept was applied in a fed-batch and a continuous process (stirred tank), without the commonly applied addition of a carrier solvent. The synthesis of peroxyoctanoic acid catalyzed by Candida antarctica lipase B was chosen as the model reaction. Here, the feasibility of this biocatalytic reaction in a single-phase system was shown for the first time. The work shows the economic superiority of the continuous process compared to the fed-batch process. Employing the fed-batch process reaction rates up to 36 mmol h−1 per gramcat, and a maximum yield of 96 % was achieved, but activity dropped quickly. In contrast, continuous operation can maintain long-term enzyme activity. For the first time, the continuous enzymatic reaction could be performed for 55 h without any loss of activity and with a space-time yield of 154 mmol L−1 h−1, which is three times higher than in the fed-batch process. The higher catalytic productivity compared to the fed-batch process (34 vs. 18 gProd g−1cat) shows the increased enzyme stability in the continuous process.

Over-expression of chloroperoxidase in Caldariomyces fumago

Abstract: The filamentous fungus Caldariomyces fumago secretes a chloroperoxidase (CPO). To increase its production, we integrated a CPO-expression cassette into the non-transcribed spacer regions of the rDNA in C. fumago. One strain was obtained that had twice the CPO activity when grown in shake-flask and bioreactor compared to the wild-type. The highest CPO activity from the bioreactor cultivation was 3,236 U ml(-1). This is the highest value reported so far.

Elektrochemische und chemische Korrosionsprüfung von 13%igem Chrom‐StahlguM in chloridhaltigen Medien

Abstract: Die Korrosionsgeschwindigkeiten von 13/1-CrNi-, 13/4-CrNi-, 12/5/1-CrNiMo- und 14/5/1-CrNiMo-Stahlgus werden in 3%iger NaCl-Losung, Meerwasser und in 2 n H2SO4 mit bis zu 0,35 n NaCl auf elektrochemischem Wege durch Messung der Steigung der Stromdichte-Potential-Kurve beim Korrosionspotential sowie chemisch durch Analyse ermittelt. In 3%ioger NaCl-Losung ergibt sich nach beiden Methodes cine Abstufung in des Reine 13/1-, 12/5/1-, 13/4- und 14/5/1- CrNiMo mit Werten von 0,7 bis 0,2 g/m2d bei 40° C und von 0,4 bis 0,1 bei 20° C. Diese Resultate bestatigen die quantitative Ubereinstimmung sowohl von elektrochemischer und chemischer Bestimmungs-methode als auch von Kurz- und Lang-zeitversuch. Neben dem Einflus der Stromung werden die Gesamt-Stromspan-nungskurven in verschiedenen Medien bestimmt und interpretiert sowie eine Apparatur zur Ermittlung von Korrosions-geschwindigkeiten im Bereich von 1000 g/m2d bis 0,003 g/m2d beschrieben. Electrochemical and chemical corrosion testing of 13% Cr cast steel in chloride containing media The corrosion rate of 13-1 Cr-Ni, 13-4 Cr-Ni, 12-5-1 Cr-Ni-Mo and 14-5-1 Cr-Ni-Mo cast steel is studied in 3% NaCl solution, sea water and 2 N H2SO4 containing up to 0.35 N NaCl; test methods include electrochemical ones, i.e. by measuring the slope of the current density/potential curve at the corrosion potential, and chemical methods, i.e. by analysis. In 3% NaCl solution both methods yield a series of decreasing rates (13-1, 12-5-1, 13-4 and 14-5-1 Cr-Ni-Mo cast steel), weight loses ranging from 0,7 to 0,2 g/m2d at 40° C, and from 0,4 to 0,1 g/m2d at 20° C. These results confirm the quantitative agreement between electrochemical and chemical evaluation as well as the agreement between short term and long term testing. The influence of flow is investigated and overall current density/potential curves are determined in various media and are interpreted. In addition, the authors describe an apparatus for the determination of corrosion rates between 1000 and 0,003 g/m2d.