Mid-term results of a modified arterial switch operation using the direct reconstruction technique of the pulmonary artery

Background: There is ongoing discussion as to whether it is beneficial to avoid pulmonary sinus augmentation in the arterial switch operation. We report a single-surgeon series of mid-term results for direct pulmonary artery anastomosis during switch operation for transposition of the great arteries (TGA). Methods: This retrospective study includes 17 patients with TGA, combined with an atrial septal defect, patent foramen ovale or ventricular septal defect. Patient data was analyzed from hospital charts, including operative reports, post-operative course, and regular follow-up investigations. The protocol included cardiological examination by a single pediatric cardiologist. Echocardiographic examinations were performed immediately after arrival on the intensive unit, before discharge, and then after three, six, and 12 months, followed by yearly intervals. Pulmonary artery stenosis (PAS) was categorized into three groups according to the Doppler-measured pulmonary gradient: grade I (trivial stenosis) = increased pulmonary flow with a gradient below 25 mm Hg; grade II (moderate stenosis) = a gradient ranging from 25 to 49 mm Hg; and grade III (severe stenosis) = a gradient above 50 mm Hg. Follow-up data was available for all patients. The length of follow-up ranged from 1.2 to 9.7 years, median: 7.5 years (mean 6.1 years ± 14 months). Results: During follow-up, 12 patients (70.6%) had no (or only trivial) PAS, five patients (29.4%) had moderate stenosis without progress, and no patient had severe PAS. Cardiac catheterization after arterial switch operation was performed in 11 patients (64.7%) and showed a good correlation with echocardiographic findings. During follow-up there was no reintervention for PAS. Conclusions: Direct reconstruction of the neo-pulmonary artery is a good option in TGA with antero-posterior position of the great vessels, with very satisfactory mid-term results. (Cardiol J 2010; 17, 6: 574-579

Significance of patient categorization for perioperative management of children with tetralogy of Fallot, with special regard to co-existing malformations

Background: The aim of our study was to facilitate perioperative calculation of potential risk factors on the outcome of corrective surgery for children with tetralogy of Fallot. Methods: The medical records of 81 (44 female and 37 male) out of a total of 87 patients undergoing complete surgical repair of tetralogy of Fallot between 1988 and 2004 at the Children’s Hospital of the Johannes Gutenberg University of Mainz were reviewed. Patients were divided into four categories, depending on the severity of pulmonary stenosis and cyanosis, as well as on the type of pulmonary circulation. Results: Additional malformations did not affect mortality rates, but did directly affect the number of pleural effusions, time of epinephrine administration, duration of surgery, bypass, and ischemia, as well as length of hospitalization and intensive care unit treatment. In contrast to longer periods of extracorporeal circulation and ischemia during surgery, which are directly related not only to more complex anatomical situations but also to higher mortality and complication rates, the much-debated question of age at surgery had no influence either on the surgical approach itself or on the post-operative outcome. Conclusions: Our patient categorization, and evaluation of potential pre-operative risk factors and intraoperative parameters, should prove useful for the future planning and execution of therapeutic procedures in institutions around the world. (Cardiol J 2010; 17, 1: 20-28

Cyclic triterpenoid production with tailored Saccharomyces cerevisiae

Triterpenoids are secondary plant metabolites derived from squalene and consist of six isoprene units (C30). Many of them or their synthetic derivatives are currently being investigated as medicinal products for various diseases. The cyclic triterpenoid betulinic acid is of special interest for the pharmaceutical and nutritional industry as it has antiretroviral, antimalarial, and anti-inflammatory properties and has potential as an anticancer agent (Muffler et al. 2011, Mullauer et al. 2010). Despite their obvious industrial potential, the application is often hindered by their low abundance in natural plant sources. This poses challenges in a biosustainable production of such compounds due to wasteful and costly product purification. Here, we present a novel biotechnological process for the production of betulinic acid using tailored Saccharomyces cerevisiae strains. The multi-scale optimization of this microbial process included: - pathway engineering by determination of optimal gene combination and dosage, - compartment engineering to increase the reaction space of the betulinic acid pathway, and - strain engineering by implementation of different push, pull and block strategies. In parallel we developed the fermentation process and were able to boost the performance of the engineered yeast by optimization of medium composition, cultivation conditions, carbon source and mode of fermentation operation in lab scale bioreactors. Product purification was achieved by a one-step extraction with acetone. The final process was evaluated in terms of economic and ecological efficiency and rated to be competitive with existing plant extraction procedures with potential for further performance improvement. Please click Additional Files below to see the full abstract

Malic acid production by Aspergillus oryzae

Malic acid is a C4 dicarboxylic acid which is used as an acidulant in food and beverages. It isalso considered as a bio-building block to replace petrochemically derived compounds in thepost oil era. This organic acid can be biotechnologically derived from fermentation usingrenewable feedstocks as carbon source. Aspergilli are among the best producers of organicacid and A. flavus/oryzae is the best natural producer of malic acid.The mechanism of malic acid production in A. oryzae was first assessed by transcriptomeanalysis. A nitrogen starvation response, probably regulated by a transcription factor relatedto the S. cerevisiae Msn2/4 transcriptional activator of stress related genes, was found toresult in high malic acid production. Furthermore the pyruvate carboxylase reaction wasidentified as a metabolic engineering target. This gene, together with the malatedehydrogenase and a malic acid exporter was overexpressed in the strain 2103a-68, whichwas characterized in a second project. The overexpression led to an 80% increase in yieldduring the starvation phase (1.49 mol (mol gluc)-1) and a triplication of the specificproduction rate. The increase in citric acid production in the engineered strain and itsevaluation through model simulations led to the curation of the A. oryzae GEM. The existingmodel was curated with special emphasis on the mitochondrial transport reactions and let toa more defined network around the production of organic acids. Furthermore, theperformance of the strain 2103a-68 on xylose as carbon source was evaluated as well andthe good results led to the final project of manipulating the carbon source utilization bydeleting the carbon catabolite repressor CreA.This work contributed to the understanding of the regulation of malic acid production. Thisknowledge was used for the development of A. oryzae as an organic acid producer throughmetabolic engineering. Furthermore, the evaluation of xylose as an alternative carbonsource paved the way towards the use of lignucellulosic feedstocks and showed thesuitability of A. oryzae for the biorefinery of the future

Malic acid production by Aspergillus oryzae

Malic acid is a C4 dicarboxylic acid which is used as an acidulant in food and beverages. It isalso considered as a bio-building block to replace petrochemically derived compounds in thepost oil era. This organic acid can be biotechnologically derived from fermentation usingrenewable feedstocks as carbon source. Aspergilli are among the best producers of organicacid and A. flavus/oryzae is the best natural producer of malic acid.The mechanism of malic acid production in A. oryzae was first assessed by transcriptomeanalysis. A nitrogen starvation response, probably regulated by a transcription factor relatedto the S. cerevisiae Msn2/4 transcriptional activator of stress related genes, was found toresult in high malic acid production. Furthermore the pyruvate carboxylase reaction wasidentified as a metabolic engineering target. This gene, together with the malatedehydrogenase and a malic acid exporter was overexpressed in the strain 2103a-68, whichwas characterized in a second project. The overexpression led to an 80% increase in yieldduring the starvation phase (1.49 mol (mol gluc)-1) and a triplication of the specificproduction rate. The increase in citric acid production in the engineered strain and itsevaluation through model simulations led to the curation of the A. oryzae GEM. The existingmodel was curated with special emphasis on the mitochondrial transport reactions and let toa more defined network around the production of organic acids. Furthermore, theperformance of the strain 2103a-68 on xylose as carbon source was evaluated as well andthe good results led to the final project of manipulating the carbon source utilization bydeleting the carbon catabolite repressor CreA.This work contributed to the understanding of the regulation of malic acid production. Thisknowledge was used for the development of A. oryzae as an organic acid producer throughmetabolic engineering. Furthermore, the evaluation of xylose as an alternative carbonsource paved the way towards the use of lignucellulosic feedstocks and showed thesuitability of A. oryzae for the biorefinery of the future

Investigation of Malic Acid Production in Aspergillus oryzae under Nitrogen Starvation Conditions

Malic acid has great potential for replacing petrochemical building blocks in the future. For this application, high yields, rates, and titers are essential in order to sustain a viable biotechnological production process. Natural high-capacity malic acid producers like the malic acid producer Aspergillus flavus have so far been disqualified because of special growth requirements or the production of mycotoxins. As A. oryzae is a very close relative or even an ecotype of A. flavus, it is likely that its high malic acid production capabilities with a generally regarded as safe (GRAS) status may be combined with already existing large-scale fermentation experience. In order to verify the malic acid production potential, two wild-type strains, NRRL3485 and NRRL3488, were compared in shake flasks. As NRRL3488 showed a volumetric production rate twice as high as that of NRRL3485, this strain was selected for further investigation of the influence of two different nitrogen sources on malic acid secretion. The cultivation in lab-scale fermentors resulted in a higher final titer, 30.27 +/- 1.05 g liter(-1), using peptone than the one of 22.27 +/- 0.46 g liter(-1) obtained when ammonium was used. Through transcriptome analysis, a binding site similar to the one of the Saccharomyces cerevisiae yeast transcription factor Msn2/4 was identified in the upstream regions of glycolytic genes and the cytosolic malic acid production pathway from pyruvate via oxaloacetate to malate, which suggests that malic acid production is a stress response. Furthermore, the pyruvate carboxylase reaction was identified as a target for metabolic engineering, after it was confirmed to be transcriptionally regulated through the correlation of intracellular fluxes and transcriptional changes

Investigation of Malic Acid Production in Aspergillus oryzae under Nitrogen Starvation Conditions

Malic acid has great potential for replacing petrochemical building blocks in the future. For this application, high yields, rates, and titers are essential in order to sustain a viable biotechnological production process. Natural high-capacity malic acid producers like the malic acid producer Aspergillus flavus have so far been disqualified because of special growth requirements or the production of mycotoxins. As A. oryzae is a very close relative or even an ecotype of A. flavus, it is likely that its high malic acid production capabilities with a generally regarded as safe (GRAS) status may be combined with already existing large-scale fermentation experience. In order to verify the malic acid production potential, two wild-type strains, NRRL3485 and NRRL3488, were compared in shake flasks. As NRRL3488 showed a volumetric production rate twice as high as that of NRRL3485, this strain was selected for further investigation of the influence of two different nitrogen sources on malic acid secretion. The cultivation in lab-scale fermentors resulted in a higher final titer, 30.27 +/- 1.05 g liter(-1), using peptone than the one of 22.27 +/- 0.46 g liter(-1) obtained when ammonium was used. Through transcriptome analysis, a binding site similar to the one of the Saccharomyces cerevisiae yeast transcription factor Msn2/4 was identified in the upstream regions of glycolytic genes and the cytosolic malic acid production pathway from pyruvate via oxaloacetate to malate, which suggests that malic acid production is a stress response. Furthermore, the pyruvate carboxylase reaction was identified as a target for metabolic engineering, after it was confirmed to be transcriptionally regulated through the correlation of intracellular fluxes and transcriptional changes