Microbial lifestyle engineering

Using Pseudomonas putida KT2440 as a proof-of-concept organism, this thesis was aimed at microbial lifestyle engineering for industrial applications. In this thesis, a structured approach was applied by first determining what microbial improvements industry is looking for by conducting a series of interviews with both industry and academia. Besides pinpointing the fields of interest from an industrial perspective, the interviews also clarified the limitations of the actual implementation of novel or (synthetically) adapted strains developed. Strain safety being at the top of their list, we first checked the claimed GRAS safety level of P. putida KT2440. A major obstacle for the breakthrough of P. putida KT2440 to be widely used as a biotechnological host is its obligate aerobic metabolism. In silico-directed strain improvement were initiated by the adaptation of strict aerobic P. putida KT2440 to micro-oxic and anoxic conditions. Adaptation to micro-oxic levels was done by first creating a design for a recombinant strain capable of anaerobic fermentation. The bottlenecks uncovered were resolved by insertion of three genes, and the recombinant strains were monitored through an adaptive laboratory evolution method with oxygen gradients set up specifically for this purpose. Recombinant strains were able to grow under micro-oxic conditions. Strain performance did not improve compared to the negative control under anoxic conditions. A more elaborate in-silico analysis was performed, combining protein domain analysis, transcriptomic analysis and genome-scale metabolic models to design a recombinant P. putida KT2440 strain capable of anaerobic respiration. Another general limitation in strains is their limited thermo-tolerance. We discovered a strong universal connection between NAD+ availability and thermo-tolerance. By replacing one single gene for a thermophilic heterolog in mesophilic prokaryotes, both P. putida and E. coli showed instant improved thermo-tolerance. Insertion of the aspartate NAD+ biogeneration pathway in eukaryotic yeast S. cerevisiae resulted in a similar effect. To determine the value of this thermo-tolerance in industry, a down-scaled microfluidics system was developed to mimic temperature fluctuations occurring in large scale  bioreactors. The novel discovery between thermo-tolerance and NAD+ availabilty was patented

'Doorbreek de stilte rond nanotechnologie in voedsel'

Levensmiddelenbedrijven vertellen liever niet dat hun eten uit de fabriek komt. Gevaarlijk, zegt Frans Kampers van de Agrotechnolgy & Food Sciences Group. Want als er iets misgaat, zal een ongeïnformeerde consument helemaal in paniek raken

Varroa wel of niet met pseudoschorpioenen te bestrijden?

Bestrijdingsmiddelen tegen Varroa zijn voorlopig een noodzakelijk kwaad en de toepassing luistert nauw. Indien niet goed gebruikt zijn ze ineffectief, is er kans op residue in de honing, dode bijen of resistentie bij de varroa. Bestaat er een goedwerkende, liefst biologische, bestrijding zonder die risico's? Bijvoorbeeld met pseudoschorpioenen? Twee bachelorstudenten Biologie in Utrecht doken in de literatuur en deden een aantal proeven

The Influence of Melatonin and Light on VEGF Secretion in Primary RPE Cells

(1) Background: Retinal pigment epithelial cells (RPE) cells constitutively secrete vascular endothelial growth factor (VEGF) in the retina, protecting the neuronal cells and the choroid. Increased VEGF secretion, however, can result in neovascularization and edema. Many factors regulate VEGF secretion. In this study, we investigated the effect of external stimuli in relation to diurnal rhythm on constitutive VEGF secretion. (2) Methods: Single-eye RPE cell culture was prepared from porcine eyes. RPE cells were cultured in darkness, treated with daylight or room light, and treated with melatonin at different time frames, either respectively or in combination. Supernatants were collected and VEGF content evaluated using ELISA. Expression of the clock protein BMAL1 was evaluated with Western blot. (3) Results: VEGF secretion of the RPE shows a diurnal rhythm. While the rhythm is not influenced by either light or melatonin, the amount of secreted VEGF can be increased by nocturnal melatonin, especially in combination with morning daylight. These findings disclose another layer of VEGF regulation in the retina

Perioperative morbidity of different operative approaches in early cervical carcinoma: a systematic review and meta-analysis comparing minimally invasive versus open radical hysterectomy

Purpose: Radical hysterectomy and pelvic lymphadenectomy is the standard treatment for early cervical cancer. Studies have shown superior oncological outcome for open versus minimal invasive surgery, but peri- and postoperative complication rates were shown vice versa. This meta-analysis evaluates the peri- and postoperative morbidities and complications of robotic and laparoscopic radical hysterectomy compared to open surgery. Methods: Embase and Ovid-Medline databases were systematically searched in June 2020 for studies comparing robotic, laparoscopic and open radical hysterectomy. There was no limitation in publication year. Inclusion criteria were set analogue to the LACC trial. Subgroup analyses were performed regarding the operative technique, the study design and the date of publication for the endpoints intra- and postoperative morbidity, estimated blood loss, hospital stay and operation time. Results: 27 studies fulfilled the inclusion criteria. Five prospective, randomized-control trials were included. Meta-analysis showed no significant difference between robotic radical hysterectomy (RH) and laparoscopic hysterectomy (LH) concerning intra- and perioperative complications. Operation time was longer in both RH (mean difference 44.79 min [95% CI 38.16; 51.42]), and LH (mean difference 20.96 min; [95% CI − 1.30; 43.22]) than in open hysterectomy (AH) but did not lead to a rise of intra- and postoperative complications. Intraoperative morbidity was lower in LH than in AH (RR 0.90 [0.80; 1.02]) as well as in RH compared to AH (0.54 [0.33; 0.88]). Intraoperative morbidity showed no difference between LH and RH (RR 1.29 [0.23; 7.29]). Postoperative morbidity was not different in any approach. Estimated blood loss was lower in both LH (mean difference − 114.34 [− 122.97; − 105.71]) and RH (mean difference − 287.14 [− 392.99; − 181.28]) compared to AH, respectively. Duration of hospital stay was shorter for LH (mean difference − 3.06 [− 3.28; − 2.83]) and RH (mean difference − 3.77 [− 5.10; − 2.44]) compared to AH. Conclusion: Minimally invasive radical hysterectomy appears to be associated with reduced intraoperative morbidity and blood loss and improved reconvalescence after surgery. Besides oncological and surgical factors these results should be considered when counseling patients for radical hysterectomy and underscore the need for new randomized trials. © 2021, The Author(s)

In-situ X-Ray Absorption Near Edge Structure Spectroscopy of a Solid Catalyst using a Laboratory-Based Set-up

An in-situ laboratory-based X-ray Absorption Near Edge Structure (XANES) Spectroscopy set-up is presented, which allows performing long-term experiments on a solid catalyst at relevant reaction conditions of temperature and pressure. Complementary to research performed at synchrotron radiation facilities the approach is showcased for a Co/TiO2 Fischer-Tropsch Synthesis (FTS) catalyst. Supported cobalt metal nanoparticles next to a (very small) fraction of cobalt(II) titanate, which is an inactive phase for FTS, were detected, with no signs of re-oxidation of the supported cobalt metal nanoparticles during FTS at 523 K, 5 bar and 200 h, indicating that cobalt metal is maintained as the main active phase during FTS.Peer reviewe