[Performance and cost calculation for a university ophthalmological outpatient clinic]. / Leistungs- und Kostenkalkulation für eine universitäre, augenheilkundliche Hochschulambulanz.

BACKGROUND: Outpatient procedures at a university hospital are generally considered to be unprofitable. In the present publication we evaluate the turnover and costs of the university eye outpatient department of the Hannover Medical School (MHH) in terms of a cost unit accounting as well as providing a summary of the workload. MATERIAL AND METHOD: Given the data of the hospital information system (IS-H/i.s.h.med from SAP) and a proprietary software (TimeElement), all patient contacts in the year 2019 were evaluated. The latter software is applied in a standardized manner to record the patient flow of our outpatient service in real time electronically. The total costs consist of personnel, material and room costs including infrastructure of the MHH and are compared to the flat-rate revenues according to the university outpatient contract (HSA) as well as further revenues from internal referral services, self-pay patients, outpatient surgery and cooperation contracts for intravitreal injections (IVOM). RESULTS: With an average full-time equivalent (FTE) headcount of 10.63 assistant physicians, 3.6 specialist physicians, and 21 nonphysicians (plus 4 Federal Volunteer Service, BUFDI) in our policlinic, we have determined €â€¯2,927,022 in personnel costs, including overheads, for the entire year. Including infrastructure (€â€¯524,942), material and equipment costs with overheads and internal cost allocation of €â€¯258.657, the total costs in 2019 resulted in €â€¯3,710,621. In contrast, the total income in 2019 was €â€¯3,524,737 generated through the abovementioned patient segments, resulting in a deficit of €â€¯-185,884 (5%). Our data provide evidence that regular outpatient revenues are insufficient and are mainly balanced by outpatient surgery, IVOMs and self-pay patients. In total, there were 19,453 patient contacts during regular office hours (with 17,305 billable cases). At n = 9943, the majority of the contacts were HSA visits; however, only 82% of the cases could effectively be charged due to multiple visits per quarter. The median total patient attendance was 3.21 h (mean 3.38 h). On average, 78 patient contacts were counted per working day. The analysis with TimeElement unveiled a median of n = 2 physician contacts per patient (mean n = 1.91). The median duration per interaction with a physician was 17.98 min (mean 23.23 min). For diagnostics, we counted a median of n = 2 interactions per patient (mean n = 2.31), with an entire interaction lasting a median of 18.30 min (mean 22.60 min). In total n = 37,363 individual diagnostic procedures were recorded in 2019, with SD-OCT being the primary procedure at n = 10,888. CONCLUSION: The cost/turnover calculation showed a marginal financial loss through our ophthalmological outpatient department. Thus, the costs of a university eye outpatient department in Lower Saxony do not seem to be sufficiently covered by direct outpatient revenues. Maintaining quarterly flat rates for all cases of the outpatient department would require a fee of about €â€¯214 in our setting to remain cost neutral. Currently, the lower flat rates in the HSA area are compensated by other areas. Obviously, the high content-related workload in our setting requires a high personnel expenditure with a considerable personnel cost contribution of nearly 80%.

[Influence of COVID-19 shutdown on the workload of a university eye clinic]. / Einfluss des COVID-19-Shutdowns auf die Arbeitsleistung einer Universitäts-Augenpoliklinik.

BACKGROUND: The outbreak of the novel coronavirus disease 2019 (COVID-19) has led to a significant reduction in the number of patients treated in elective medicine in hospitals in spring 2020. Up until now, there are no corresponding data for university policlinics. MATERIAL AND METHODS: With the help of the data of the clinic's electronic medical record system (IS-H/i.s.h.med from SAP, Cerner Corporation, North Kansas City, MO, United States of America and SAP SE, Walldorf, Germany) and the time recording and management software TimeElement (Hannover Medical School, Hannover, Germany), which was codeveloped at our clinic, all patient contacts of the COVID-19 shutdown were evaluated over a period of approximately 7 weeks from 18 March 2020 to 8 May 2020 and compared with the same period in 2019. In addition, quarterly revenues for the first and second quarters of 2019 and 2020 were put into perspective via SAP. RESULTS: During the COVID-19 period the total number of patient contacts was reduced by 59.5% compared to the previous year. The number of lockdown period cases decreased by 74.8% compared to the same period in 2019. In particular, the university outpatient/self-paying sector recorded the largest number of lost patient contacts with a reduction to 17.2% of the 2019 baseline. The reduced patient contacts and case numbers resulted in a significant financial loss of at least €â€¯218,000. Via TimeElement there was a 69.4% decrease in all special diagnostic services, with visual field examinations in particular also reduced by 75.3%. Optical coherence tomography (OCT) measurements recorded a decrease of 60.3%. Patient tracking revealed a reduction of average patient attendance times by approximately 23% (COVID 19: 145.8 ± 88.8 min versus 189.6 ± 97.2 min in 2019). DISCUSSION: The COVID-19 shutdown caused the work performance of our policlinic to drop to only about 40% of patient contacts and that of functional diagnostic examinations to only about 30%, compared to the performance in 2019; however, the reduction in the number of patients also led to a significant reduction in the time patients were present at the clinic compared to the regular workload. The associated financial losses are considerable and obviously not compensated by legally regulated compensation payments as in the inpatient sector.

[Clinical diagnostics and therapy for non-arteritic central retinal artery occlusion]. / Diagnostik und Therapie beim nicht arteriitischen Zentralarterienverschluss.

Central retinal artery occlusion (CRAO) is an ophthalmological emergency situation. Known risk factors are arterial hypertension, cardial arrhythmia, arteriosclerosis, hypercholesterolemia and diabetes. Elderly patients should be examined for an arteritic genesis. Young patients (< 45 years) without typical risk factors may suffer from thrombophilia. There is no uniform recommendation on how to treat non-arteritic CRAO. Many different interventions have been suggested in the literature, i. e., massaging the eye, systemic or local reduction of intraocular pressure, anticoagulation, either systemically administered venous thrombolysis or supraselective intra-arterial thrombolysis. In this review we present the causes of CRAO and diagnostic means to detect causes; we also critically discuss previously described therapeutic options. It is our aim to provide a guide through the necessary interdisciplinary diagnostics in co-operation with internal medicine and neurology and to recommend a multimodal therapy in patients with non-arteritic CRAO.

Resolving the clinical acuity categories "hand motion" and "counting fingers" using the Freiburg Visual Acuity Test (FrACT).

PURPOSE: The Freiburg Visual Acuity Test (FrACT) has been suggested as a promising test for quantifying the visual acuity (VA) of patients with very low vision, a condition often classified using the semi-quantitative clinical scale "counting fingers" (CF), "hand motion" (HM), "light perception" (LP) and "no light perception". The present study was designed to assess FrACT performance in a sizable number of CF, HM, and LP patients in order to generate a setting for future clinical studies in the low vision range. METHODS: We examined a total of 41 patients (LP, n = 11; CF, n = 15; HM, n = 15) with various eye diseases (e.g., diabetic retinopathy, ARMD), covering the clinical VA scale from LP to CF. The FrACT optotypes were presented at a distance of 50 cm on a 17-inch LCD monitor with four random orientations. After training, two FrACT measurements (test and retest) were taken, each comprising 30 trials. RESULTS: FrACT measures reproducibly the VA of CF and HM patients. In CF patients, FrACT resulted in a mean logMAR = 1.98 +/- 0.24 (corresponding to a decimal VA of 0.010), for HM in a mean logMAR = 2.28 +/- 0.15 (corresponding to a decimal VA of 0.0052). In all LP patients the FrACT values were close to what would be obtained by random guessing. The mean test-retest 95% confidence interval was 0.21 logMAR for CF patients and 0.31 logMAR for HM respectively. Test-retest variability declined from 24 to 30 trials, showing that at least 30 trials are necessary. CONCLUSION: FrACT can reproducibly quantify VA in the CF and HM range. We observed a floor effect for LP, and it was not quantifiable further. Quantitative VA measures are thus obtainable in the very low-vision range using FrACT.

[Bruch's membrane opening minimum rim width : Correlation and diagnostic accuracy in comparison to peripapillary retinal nerve fiber layer thickness]. / Die auf der Bruchschen Membranöffnung basierende Minimale Randsaumweite : Korrelation und diagnostische Genauigkeit im Vergleich zur peripapillären retinalen Nervenfaserschichtdicke.

BACKGROUND: Glaucoma is one of the main causes of blindness in the Western hemisphere. Because the disease often painlessly progresses it remains unnoticed until major optic nerve head damage occurs in many cases. That is why new, more sensitive diagnostic methods are needed. Bruch's membrane opening minimum rim width (BMO-MRW), measured with the new glaucoma module premium edition (GMPE) was recently introduced as a more accurate tool to detect glaucomatous changes. The purpose of this study was to assess the correlation of SPECTRALIS® spectral domain optical coherence tomography (SD-OCT) and the GMPE anatomic positioning module (APS module) for retinal nerve fiber layer thickness (RNFLT) measurements. The second aim was to assess the diagnostic accuracy of BMO-MRW. METHODS: Prospective study of 41 eyes (41 patients) with glaucoma and 26 eyes from 26 healthy controls. Scans were obtained using SPECTRALIS® SD-OCT and RNFLT was measured with both modules and compared using Spearman's rank test. The BMO-MRW was assessed by GMPE. Sensitivity, specificity and area under receiver operating characteristics curves (AUROC) of each sector of the optic nerve were calculated and compared using the method of Delong et al. RESULTS: We found a positive correlation (0.694-0.955, p < 0.0001) between RNFLT measurements by standard SD-OCT and all diameters of RNFLT of APS module within all sectors. The AUROC of RNFLT in standard SD-OCT was 0.693 for the inferior nasal sector (NI) and BMO-MRW was 0.85 in NI. The difference in AUROC was statistically significant (p = 0.0049). No other sector showed statistically significant differences. CONCLUSION: The RNFLT measurements of both modules showed a positive correlation and appear to be comparable. The BMO-MRW in one sector (NI) showed a significantly higher accuracy of measurement than standard RNFLT. All other sectors showed a comparable accuracy of measurement.

Studies on MIP-2 and CXCR2 expression in a mouse model of extrahepatic colorectal metastasis.

AIMS: The CXC chemokine macrophage inflammatory protein (MIP)-2 has been shown to promote outgrowth of colorectal liver metastasis by enhancing angiogenesis and tumor cell migration. However, the effect of MIP-2 on extrahepatic metastasis is not known yet. With a use of a murine model, we therefore studied cell proliferation and microvascularization of extrahepatic CT26.WT-GFP colorectal tumors after exposure to MIP-2. METHODS: Green fluorescent protein (GFP)-transfected CT26.WT colorectal cancer cells were implanted in dorsal skinfold chambers of syngeneic BALB/c mice. After 5 days, the tumors were locally exposed to 100 nM MIP-2. Cell proliferation as well as tumor microvascularization and growth were studied during a further 9-day period using intravital fluorescence microscopy, histology and immunohistochemistry. Tumors exposed to PBS served as controls. RESULTS: MIP-2 induced a marked CXCR2 expression and promoted a distinct tumor cell proliferation. This was associated with a significant increase of tumor size compared to PBS-treated controls. Of interest, MIP-2 did not affect dilation and permeability of the tumor microvessels, which would be indicators for an enhanced VEGF action. Accordingly, the angiogenic response, e.g. the outgrowth of new microvessels, was not affected, and the density of the established tumor microvascular network was even found decreased after MIP-2 exposure when compared to PBS controls. CONCLUSION: With the use of a murine tumor model, we demonstrate that MIP-2 accelerates growth of experimentally established extrahepatic colorectal metastases by inducing tumor cell proliferation rather than promoting vascularization.

[Retinal angiomatosis. Ocular manifestation of von Hippel-Lindau disease]. / Angiomatosis retinae. Okuläre Manifestation des Von-Hippel-Lindau-Syndroms.

Von Hippel-Lindau disease (VHL disease) is a rare multisystem disorder of autosomal dominant inheritance with high penetrance. Inactivation of the VHL-protein leads to an increased expression of hypoxia induced growth factors. Predilection sites for tumor growth are the retina, the central nervous system and various visceral organs. Retinal capillary hemangioblastoma is one of the earliest manifestations of VHL disease. The lifetime risk of permanent visual loss defined as a visual acuity of 0.5 or less is about 35% in gene carriers. It increases to 60% if there is already retinal capillary hemangioblastoma. If VHL disease is suspected, a careful ophthalmological examination should be included in the clinical screening program. Having confirmed the diagnosis, regular ophthalmoscopic monitoring is essential in order to detect developing tumors at an early stage. Therapeutic options for small to medium sized peripheral tumors are laser or cryocoagulation; larger- hemangioblastomas can be treated by brachytherapy using ruthenium plaques, while asymptomatic juxtapapillary tumors can be observed at regular intervals.

[Von Hippel-Lindau disease. Interdisciplinary patient care]. / Von-Hippel-Lindau-Erkrankung. Interdisziplinäre Patientenversorgung.

Von Hippel-Lindau disease is an important hereditary tumor syndrome with a clear option for effective treatment if diagnosed in time. Interdisciplinary cooperation is the key to successful management. Major components of the disease are retinal capillary hemangioblastomas, hemangioblastomas of cerebellum, brain stem and spine, renal clear cell carcinomas, pheochromocytomas, multiple pancreatic cysts and islet cell carcinomas, tumors of the endolymphatic sac of the inner ear, and cystadenomas of the epididymis and broad ligament. A well structured screening program should be performed at yearly intervals.

[Software-based visualization of patient flow at a university eye clinic]. / Elektronische Visualisierung des ambulanten Patientenflows in einer Universitäts-Augenklinik.

OBJECTIVE: This article presents a method for visualization and navigation of patient flow in outpatient eye clinics with a high level of complexity. MATERIAL AND METHODS: A network-based software solution was developed targeting long-term process optimization by structural analysis and temporal coordination of process navigation. RESULTS: Each examination unit receives a separate waiting list of patients in which the patient flow for every patient is recorded in a timeline. Time periods and points in time can be executed by mouse clicks and the desired diagnostic procedure can be entered. Recent progress in any of these diagnostic requests, as well as a variety of information on patient progress are collated and drawn into the corresponding timeline which can be viewed by any of the personnel involved. The software called TimeElement has been successfully tested in the practical implemenation for several months. As an example the patient flow regarding time stamps of defined events for intravitreous injections on 250 patients was recorded and an average attendance time of 169.71 min was found, whereby the time was also automatically recorded for each individual stage. CONCLUSION: Recording of patient flow data is a fundamental component of patient flow management, waiting time reduction, patient flow navigation with time and coordination in particular regarding timeline-based visualization for each individual patient. Long-term changes in process management can be planned and evaluated by comparing patient flow data. As using the software itself causes structural changes within the organization, a questionnaire is being planned for appraisal by the personnel involved.

Development of a highly productive and scalable plasmid DNA production platform.

With the applications of DNA vaccines extending from infectious diseases to cancer, achieving the most efficient, reproducible, robust, scalable, and economical production of clinical grade plasmid DNA is paramount to the medical and commercial success of this novel vaccination paradigm. A first generation production process based on the cultivation of Escherichia coli in a chemically defined medium, employing a fed-batch strategy, delivered reasonable volumetric productivities (500-750 mg/L) and proved to perform very well across a wide range of E. coli constructs upon scale-up at industrial scale. However, the presence of monosodium glutamate (MSG) in the formulation of the cultivation and feed solution was found to be a potential cause of process variability. The development of a second generation process, based on a defined cultivation medium and feed solution excluding MSG, was undertaken. Optimization studies, employing a plasmid coding for the HIV gag protein, resulted in cultivation conditions that supported volumetric plasmid titers in excess of 1.2 g/L, while achieving specific yields ranging from 25 to 32 microg plasmid DNA/mg of dry cell weight. When used for the production of clinical supplies, this novel process demonstrated applicability to two other constructs upon scale-up in 2,000-L bioreactors. This second generation process proved to be scalable, robust, and highly productive.

[Intraoperative optical coherence tomography in retinal detachment]. / Intraoperative optische Kohärenztomographie bei Ablatio retinae.

BACKGROUND: Using intraoperative optical coherence tomography (iOCT) can be advantageous during macular surgery and lamellar keratoplasty. It is yet unknown if there is a distinct benefit in its application in retinal detachment surgery. OBJECTIVE: What can be shown using iOCT during retinal detachment surgery? Can therapeutically relevant decisions be made and do they have a prognostic implication on postoperative results? METHODS: Based on already published (11 patients/eyes) and our own new data (23 patients/eyes),findings by iOCT during retinal detachment surgery are presented. RESULTS: Outer retinal corrugations are a frequent feature in iOCT in retinal detachment. These corrugations persist during the application of heavy liquids. Even when the retina seems clinically reattached under the use of perfluoroctane, there is significant subfoveal fluid. Using perfluordecaline, there seems to be less subfoveal fluid. In patients with retinal detachment and macula off situation, subclinical full thickness macular holes seem to be more common than assumed. It is unclear if their incidence is influenced by the use of heavy liquids. They appear to have a negative predictive value regarding postoperative visual acuity. CONCLUSION: Even if there are no obvious benefits in using iOCT in retinal detachment surgery, this new technique offers deeper insights into the microarchitecture of the detached retina. Further investigations in more patients will show if the use of the iOCT will result in a better prognosis for our patients.

[Intraoperative real-time OCT in macular surgery]. / Intraoperative Echtzeit-OCT in der Makulachirurgie.

BACKGROUND: Spectral domain optical coherence tomography (SD-OCT) has become a standard diagnostic tool in the surgical management of vitreomacular interface disorders. The high-resolution cross-sectional information obtained from SD-OCT is a perfect complement to vitreoretinal surgery. It provides detailed intraoperative anatomical views that are not possible with a microscope. OBJECTIVE: To investigate the value of intraoperative real-time OCT with respect to improvement of surgical techniques in the management of vitreomacular disorders. METHODS: A review of the current literature was conducted and an analysis of own systematically evaluated data was included to provide a comprehensive overview of potential applications for the clinical use of intraoperative real-time OCT in macular surgery. RESULTS: Intraoperative real-time OCT can provide detailed visualization of epiretinal membranes and help to identify whether complete membrane removal has been achieved following surgery. In addition, it can provide qualitative and quantitative information that has previously not been available and assist in surgical decision-making. Intraoperative real-time OCT allows membrane peeling to be performed in selected cases without using retinal dyes, whereas it is not ideal for accurately guiding the surgeon while performing maneuvers. CONCLUSION: Intraoperative real-time OCT provides high-resolution visualization of the effects of surgical maneuvers on the microarchitecture of the retina and surrounding tissues and will fill a gap in the understanding of the pathophysiology and prognostic factors of vitreomacular disorders; however, with currently available systems, accurate intraoperative real-time guidance of surgical maneuvers is hindered by several limiting factors.

Latency studies on rat liver microsomal glucose-6-phosphatase. Correlation of membrane modification and solubilization by Triton X-114 with the enzymatic activity.

Interrelationships between the catalytic properties of glucose-6-phosphatase and the membrane structure of rat liver microsomes were investigated. Membrane modification and solubilization employing the nonionic surfactant Triton X-114 were standardized and analysed by ultracentrifugation, surface tension- and turbidity measurements. The effect of Triton X-114 on the glucose-6-phosphatase activity was studied systematically and the whole magnitude of time- and temperature-dependent inactivation of this enzyme has been demonstrated. The results show that the activity measured is always a resultant of two processes, the beginning of inactivation and the release of latency. Maximal activation of about 600% (83% of apparent latency) was obtained at 0 degree C. A correlation between membrane modification and solubilization and the conditions under preincubation and test incubation reveals that studies on detergent-disrupted microsomes are performed on structures reassembled from solubilizates and this implies a modified microenvironment in the reconstitutes. Kinetic analyses suggest interrelationships between Triton X-114 and the permeability barrier of the glucose-6-phosphatase system. At 0 degree C 2-propanol and ethanol are more potent tools for membrane modification than Triton X-114 and release 88% and 86% latent activity corresponding to an activation of the glucose-6-phosphatase of about 850% and 700%, respectively. These observations suggest that detergent treatment of microsomes could not preserve the functional integrity of the glucose-6-phosphate phosphohydrolase, which is one dogma of the substrate-transport hypothesis developed by Arion and his co-workers (Arion, W.J., et al. (1975) Mol. Cell. Biochem. 6, 75-83).

Exploratory statistical methods, with applications to psychiatric research.

This article introduces statistical methods for describing and summarizing the results of studies and introduces statistical principles that will guide the psychiatric researcher in the evaluation and interpretation of clinical research. We discuss relatively easy-to-use and informal methods for describing and comparing data. Our aim is to develop methods for investigating relationships among variables, to learn about the effect of one variable upon another. Once we have observed an apparent relationship between variables, an important question to be addressed is whether or not this observed relationship is causal in the sense that a change in one variable causes a changes in the other. We discuss and illustrate principles related to the evaluation of the nature of the association among variables. Throughout the article, principles and methods will be illustrated by examples and case studies based on data sets primarily from the psychiatric research literature.

Structure determination of a key intermediate of the enantioselective Pd complex catalyzed allylic substitution reaction

The structure of a catalytic intermediate with important implications for the interpretation of the stereochemical outcome of the palladium complex catalyzed allylic substitution with phosphino-oxazoline (PHOX) ligands is determined by liquid state NMR. The complex displays a novel structure that is highly distorted compared with other palladium eta2-olefin complexes known so far. The structure has been determined from nuclear overhauser data (NOE), scalar coupling constants, and long range projection angle restraints derived from dipole dipole cross-correlated relaxation of multiple quantum coherence. The latter restraints have been implemented into a distance geometry protocol. The projection angle restraints yield a higher precision in the determination of the relative orientation of the two molecular moieties and are essential to provide an exact structural definition of the olefinic part of the catalytic intermediate with respect to the ligand.

Secondary metabolite scale-up to minimize homolog impurity levels

A mutant strain of Streptomyces hygroscopicus was found to produce up to 9.0 units/L of an immunoregulant precursor, immunomycin, with up to 3.5% of a lower homolog impurity under either dual fed-batch or batch conditions. Glycerol and valine were key nutrients influencing productivity and impurity levels. Soybean oil was successfully substituted for glycerol as a carbon source to minimize shot additions to batch culture. The remainder of the production medium was composed largely of defined components with the exception of yeast extract. Valine limitation increased lower homolog formation while decreasing higher homolog formation; excess valine decreased lower homolog formation below 2-3% while increasing higher homolog formation. Higher homolog formation in the presence of valine seemed to be slower than lower homolog formation in the absence of valine. Valine was believed to be the major butyrate precursor; consequently its availability influenced the impurity profile. A preliminary cost analysis suggests that elimination of added valine from the cultivation and replacement of glycerol with soybean oil can result in a 6.6-fold reduction in media costs relative to the original fed-batch process. Copyright 1998 John Wiley & Sons, Inc.

Scale-up studies on a defined medium process for pilot plant production of illicicolin by Gliocladium roseum.

Illicicolin was cultivated at the 600-L pilot scale for purposes of material generation and process development. The initial medium containing oat flour was difficult operationally as a result of excessive foaming during sterilization, so a new defined medium process (with either glucose or sucrose as the carbon source), developed at the 23-L scale, was scaled up and improved for pilot scale needs. Pilot scale media development efforts focused on exploring the highest concentration of media (1.0 x to 3.0 x) that could be cultivated at the pilot scale and not be limited by mixing or oxygen mass transfer. The process was scaled up successfully and peak titers improved 7.5-fold, from about 200 mg/L in the initial complex medium to 1500 mg/L in the final defined medium.

Design and installation of a next generation pilot scale fermentation system.

Four new fermenters were designed and constructed for use in secondary metabolite cultivations, bioconversions, and enzyme production. A new PC/PLC-based control system also was implemented using GE Fanuc PLCs, Genius I/O blocks, and Fix Dynamics SCADA software. These systems were incorporated into an industrial research fermentation pilot plant, designed and constructed in the early 1980s. Details of the design of these new fermenters and the new control system are described and compared with the existing installation for expected effectiveness. In addition, the reasoning behind selection of some of these features has been included. Key to the design was the goal of preserving similarity between the new and previously existing and successfully utilized fermenter hardware and software installations where feasible but implementing improvements where warranted and beneficial. Examples of enhancements include strategic use of Inconel as a material of construction to reduce corrosion, piping layout design for simplified hazardous energy isolation, on-line calculation and control of nutrient feed rates, and the use of field I/O modules located near the vessel to permit low-cost addition of new instrumentation.

Indirect methods for characterization of carbon dioxide levels in fermentation broth.

Various factors which influence dissolved carbon dioxide levels were indirectly evaluated in pilot scale and laboratory studies. For pilot scale studies, off-gas carbon dioxide (percentage in exit air) was measured using a mass spectrometer and then its potential impact on dissolved carbon dioxide concentrations qualitatively examined. Greater volumetric air flowrates reduced off-gas carbon dioxide levels more effectively at lower airflow ranges and thus lowered expected dissolved carbon dioxide levels through gas stripping. Lower broth pH values decreased off-gas carbon dioxide levels but increased expected dissolved carbon dioxide levels due to the pH-dependence of the gas/liquid carbon dioxide equilibrium. While back-pressure increases had an insignificant effect on off-gas carbon dioxide levels, they directly affected expected dissolved carbon dioxide levels according to Henry's law. Laboratory studies, conducted using both uninoculated and inoculated fermentation media, quantified the response of the media to pH changes with bicarbonate addition, specifically its buffering capacity. This effect then was related qualitatively to expected dissolved carbon dioxide levels. Higher dissolved carbon dioxide levels, as demonstrated by reduced pH changes with bicarbonate addition, thus would be expected for salt solutions of increased ionic strength and higher protein content media. In addition, pH changes with greater bicarbonate additions declined for fermentation samples taken over the course of a one week cultivation, most likely due to the higher protein content associated with biomass growth. The presence of weak acids/bases initially in the media or formed as metabolic by products, as well as the concentration of buffering ions such as phosphate, also were believed to be important contributing elements to the buffering capacity of the solution.

Carbon and complex nitrogen source selection for secondary metabolite cultivation at the pilot scale.

The fermentation of desmethyl-asterriquinone B-1, a diabetes target, by a Pseudomonasarias species was conducted at the 600-l scale using a revised complex medium containing yeast extract and soy hydrolysate. Oat flour and tomato paste were removed from this medium due to difficulties in sterilization. An initial cerelose charge of 40 g/l improved titer and reduced product degradation in the broth at cultivation conditions. An initial mannitol concentration of 65 g/l effectively avoided mid-cycle mannitol additions necessary for the 40 g/l mannitol concentration without the reduction in productivity seen at 90 g/l mannitol. These additions diluted the broth because of the low aqueous solubility of mannitol. Titers reached 3.0 g/l after 158 h with an optimized process, increasing two-fold from the original medium and operating conditions. Reproducible foaming occurred at the point of glucose exhaustion when the culture switched to mannitol consumption. Use of alternative carbon sources (glycerol, soybean oil, sorbitol in conjunction with cerelose) was not effective in attaining similar productivity and did not reduce the extent of foaming. In the case of fructose, the extent of foaming was markedly reduced but product formation was negligible.