Internal Illumination to Overcome the Cell Density Limitation in the Scale-up of Whole-Cell Photobiocatalysis

Cyanobacteria have the capacity to use photosynthesis to fuel their metabolism, which makes them highly promising production systems for the sustainable production of chemicals. Yet, their dependency on visible light limits the cell‐density, which is a challenge for the scale‐up. Here, it was shown with the example of a light‐dependent biotransformation that internal illumination in a bubble column reactor equipped with wireless light emitters (WLEs) could overcome this limitation. Cells of the cyanobacterium Synechocystis sp. PCC 6803 expressing the gene of the ene‐reductase YqjM were used for the reduction of 2‐methylmaleimide to (R)‐2‐methylsuccinimide with high optical purity (>99 % ee). Compared to external source of light, illumination by floating wireless light emitters allowed a more than two‐fold rate increase. Under optimized conditions, product formation rates up to 3.7 mm h(−1) and specific activities of up to 65.5 U g(DCW) (−1) were obtained, allowing the reduction of 40 mm 2‐methylmaleimide with 650 mg isolated enantiopure product (73 % yield). The results demonstrate the principle of internal illumination as a means to overcome the intrinsic cell density limitation of cyanobacterial biotransformations, obtaining high reaction rates in a scalable photobioreactor

Asymmetric Whole-Cell Bio-Reductions of (R)-Carvone Using Optimized Ene Reductases

(2R,5R)-dihydrocarvone is an industrially applied building block that can be synthesized by site-selective and stereo-selective C=C bond bio-reduction of (R)-carvone. Escherichia coli (E. coli) cells overexpressing an ene reductase from Nostoc sp. PCC7120 (NostocER1) in combination with a cosubstrate regeneration system proved to be very effective biocatalysts for this reaction. However, the industrial applicability of biocatalysts is strongly linked to the catalysts’ activity. Since the cell-internal NADH concentrations are around 20-fold higher than the NADPH concentrations, we produced E. coli cells where the NADPH-preferring NostocER1 was exchanged with three different NADH-accepting NostocER1 mutants. These E. coli whole-cell biocatalysts were used in batch operated stirred-tank reactors on a 0.7 l-scale for the reduction of 300 mM (R)-carvone. 287 mM (2R,5R)-dihydrocarvone were formed within 5 h with a diasteromeric excess of 95.4% and a yield of 95.6%. Thus, the whole-cell biocatalysts were strongly improved by using NADH-accepting enzymes, resulting in an up to 2.1-fold increased initial product formation rate leading to a 1.8-fold increased space-time yield when compared to literature

Switchable Signaling Molecules for Media Modulation: Fundamentals, Applications, and Research Directions

Although visionary applications of molecular communication (MC), such as long-term continuous health monitoring by cooperative in-body nanomachines, have been proposed, MC is still in its infancy when it comes to practical implementation. In particular, long-term experiments and applications face issues such as depletion of signaling molecules (SMs) at the transmitter (TX) and inter-symbol interference (ISI) at the receiver (RX). To overcome these practical challenges, a new class of SMs with switchable states seems to be promising for future MC applications. In this work, we provide an overview of existing switchable SMs, and classify them according to their properties. Furthermore, we highlight how switchable SMs can be utilized as information carriers for media modulation. In addition, we present theoretical and experimental results for an end-to-end MC system employing the green fluorescent protein variant "Dreiklang" (GFPD) as switchable SM. Our experimental results show, for the first time, successful information transmission in a closed-loop pipe system using media modulation. Finally, we discuss media modulation specific challenges and opportunities.Comment: 7 pages, 6 figures. This work has been accepted for publication in IEEE Communications Magazin

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

Correction to: Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

The original version of this article unfortunately contained a mistake

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

Polymersomes as Nanoreactors Enabling the Application of Solvent‐Sensitive Enzymes in Different Biphasic Reaction Setups

There is an increasing interest in biocatalysis to perform chemical reactions in biphasic systems, consisting of an aqueous phase and a water‐immiscible organic solvent or ionic liquid. In most cases, the hydrophobic phase is used as reservoir for poorly water‐soluble substrates or for in situ product removal. However, many enzymes are solvent‐sensitive and cannot be used in such systems. In this study, the solvent‐sensitive enzyme mandelate racemase is exemplarily protected from the organic phase by its entrapment in (crosslinked) polymersomes. The covalent crosslinking of the individual chains of the block copolymer poly(2‐methyloxazoline)15‐poly(dimethylsiloxane)68‐poly(2‐methyloxazoline)15 via terminal methacrylates leads to enhanced membrane stability. This effect is especially pronounced for long‐time incubation in the presence of organic solvents and ionic liquids. By using a gentle polymerization initiator at its minimal necessary concentration, the prior encapsulated enzymes remain intact during crosslinking. Although the insertion of natural channel proteins into the membrane improves the mass transport into the vesicles, it is non‐essential. Mandelate racemase in (crosslinked) polymersomes remains active in different highly dispersed biphasic systems for more than 24 h. The free enzyme, on the other hand, gets completely inactivated within 1 h, thus illustrating the potential of polymersomes as nanoreactors in biphasic reaction setups

Light-Driven Biocatalysis in Liposomes and Polymersomes: Where Are We Now?

The utilization of light energy to power organic-chemical transformations is a fundamental strategy of the terrestrial energy cycle. Inspired by the elegance of natural photosynthesis, much interdisciplinary research effort has been devoted to the construction of simplified cell mimics based on artificial vesicles to provide a novel tool for biocatalytic cascade reactions with energy-demanding steps. By inserting natural or even artificial photosynthetic systems into liposomes or polymersomes, the light-driven proton translocation and the resulting formation of electrochemical gradients have become possible. This is the basis for the conversion of photonic into chemical energy in form of energy-rich molecules such as adenosine triphosphate (ATP), which can be further utilized by energy-dependent biocatalytic reactions, e.g. carbon fixation. This review compares liposomes and polymersomes as artificial compartments and summarizes the types of light-driven proton pumps that have been employed in artificial photosynthesis so far. We give an overview over the methods affecting the orientation of the photosystems within the membranes to ensure a unidirectional transport of molecules and highlight recent examples of light-driven biocatalysis in artificial vesicles. Finally, we summarize the current achievements and discuss the next steps needed for the transition of this technology from the proof-of-concept status to preparative applications