Experimental pulse technique for the study of microbial kinetics in continuous culture

A novel technique was developed for studying the growth kinetics of microorganisms in continuous culture. The method is based on following small perturbations of a chemostat culture by on-line measurement of the dynamic response in oxygen consumption rates. A mathematical model, incorporating microbial kinetics and mass transfer between gas and liquid phases, was applied to interpret the data. Facilitating the use of very small disturbances, the technique is non-disruptive as well as fast and accurate. The technique was used to study the growth kinetics of two cultures, Methylosinus trichosporium OB3b growing on methane, both in the presence and in the absence of copper, and Burkholderia (Pseudomonas) cepacia G4 growing on phenol. Using headspace flushes, gas blocks and liquid substrate pulse experiments, estimates for limiting substrate concentrations, maximum conversion rates Vmax and half saturation constants Ks could rapidly be obtained. For M. trichosporium OB3b it was found that it had a far higher affinity for methane when particulate methane monooxygenase (pMMO) was expressed than when the soluble form (sMMO) was expressed under copper limitation. While for B. cepacia G4 the oxygen consumption pattern during a phenol pulse in the chemostat indicated that phenol was transiently converted to an intermediate (4-hydroxy-2-oxovalerate), so that initially less oxygen was used per mole of phenol.

Trichloroethene Degradation in a Two-Step System by Methylosinus trichosporium OB3b. Optimization of System Performance: Use of Formate and Methane

The breakdown of dissolved TCE in a two-step bioremediation system is described. In the first reactor, the organism Methylosinus trichosporium OB3b is grown; in the second reactor, consisting of three 17-L column reactors in series, the cells degrade TCE. A special design allowed both for the addition of air (uG,s = 0.01–0.04 mm s−1) in the conversion reactor to prevent oxygen limitation while minimizing stripping of TCE, and for the use of methane as exogenous electron donor. In two-step systems presented thus far, only formate was used (excess, 20 mM). We found formate additions could be reduced by 75% (15°C), whereas small amounts of methane (0.02–0.04 mol CH4/g cells) could replace formate and led to equally optimal results. Example calculations show that up to 90% reduction in operating cost of chemicals can be obtained by using methane instead of formate. A model was developed to describe each of the conditions studied: excess formate and optimal methane addition, suboptimal formate addition and suboptimal methane addition. Using parameters obtained from independent batch experiments, the model gives a very good description of the overall TCE conversion in the two-step system. The system presented is flexible (oxygen/methane addition) and can easily be scaled up for field application. The model provides a tool for the design of an effective and low-cost treatment system based on methane addition in the conversion reactor.

Vulvar and vaginal neoplasia in women with inflammatory bowel disease

Immunosuppressive drugs are the cornerstone in the treatment of inflammatory bowel disease (IBD), however they are associated with an increased risk of extra-intestinal cancer. Whether the risk for female genital tract malignancies, including vulvar and vaginal cancer, is increased is less clear.Our aim was to investigate the risk of these malignancies in IBD-patients.Histopathological data of all IBD patients with a vulvar or vaginal (pre-)cancerous lesion were retrieved from the Dutch nationwide network and registry of histopathology and cytopathology from 1991 to 2015. Medical history was retrieved from patient records. Data from the Central Office for Statistics, the Dutch comprehensive cancer organization, and the IBDSL cohort were obtained to calculate the standardized, and age-adjusted incidence rates.Fifty-five patients met the inclusion criteria. A standardized incidence rate of 1.2(95% CI:0.8-1.7) for vulvar and vaginal carcinoma among adult female IBD was calculated, which did not significantly differ from the general population. The use of immunosuppressive therapy did not increase the occurrence of vulvovaginal malignancy, nor did it influence the recurrence rate. However, immunosuppressive drugs ever-users were on average 11 years younger at the time of their gynaecological diagnosis.Overall, our data do not support intensified screening for vulvar or vaginal malignancies in female IBD patients. (C) 2019 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved

Vulvar and vaginal neoplasia in women with inflammatory bowel disease

Immunosuppressive drugs are the cornerstone in the treatment of inflammatory bowel disease (IBD), however they are associated with an increased risk of extra-intestinal cancer. Whether the risk for female genital tract malignancies, including vulvar and vaginal cancer, is increased is less clear.Our aim was to investigate the risk of these malignancies in IBD-patients.Histopathological data of all IBD patients with a vulvar or vaginal (pre-)cancerous lesion were retrieved from the Dutch nationwide network and registry of histopathology and cytopathology from 1991 to 2015. Medical history was retrieved from patient records. Data from the Central Office for Statistics, the Dutch comprehensive cancer organization, and the IBDSL cohort were obtained to calculate the standardized, and age-adjusted incidence rates.Fifty-five patients met the inclusion criteria. A standardized incidence rate of 1.2(95% CI:0.8-1.7) for vulvar and vaginal carcinoma among adult female IBD was calculated, which did not significantly differ from the general population. The use of immunosuppressive therapy did not increase the occurrence of vulvovaginal malignancy, nor did it influence the recurrence rate. However, immunosuppressive drugs ever-users were on average 11 years younger at the time of their gynaecological diagnosis.Overall, our data do not support intensified screening for vulvar or vaginal malignancies in female IBD patients. (C) 2019 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.Cellular mechanisms in basic and clinical gastroenterology and hepatolog