A simple method to determine evaporation and compensate for liquid losses in small-scale cell culture systems

The oxygen dilemma: The challenge of the anode reaction for microbial electrosynthesis from CO2

Microbial electrosynthesis (MES) from CO2 provides chemicals and fuels by driving the metabolism of microorganisms with electrons from cathodes in bioelectrochemical systems. These microorganisms are usually strictly anaerobic. At the same time, the anode reaction of bioelectrochemical systems is almost exclusively water splitting through the oxygen evolution reaction (OER). This creates a dilemma for MES development and engineering. Oxygen penetration to the cathode has to be excluded to avoid toxicity and efficiency losses while assuring low resistance. We show that this dilemma derives a strong need to identify novel reactor designs when using the OER as an anode reaction or to fully replace OER with alternative oxidation reactions.

Aerobic bioreactors: condensers, evaporation rates, scale-up and scale-down

OBJECTIVES

Hydrodynamics, mixing and shear are terms often used when explaining or modelling scale differences, but other scale differences, such as evaporation, can arise from non-hydrodynamic factors that can be managed with some awareness and effort.

RESULTS

We present an engineering approach to the prediction of evaporation rates in bioreactors based on gH₂O/Nm³ of air entering and leaving the bioreactor and confirm its usefulness in a 28-run design of experiments investigating the effects of aeration rate (0.02 to 2.0 VVM), condenser temperature (10 to 20 °C), fill (2.5 to 5 kg), broth temperature (25 to 40 °C) and agitator speed (25 to 800 rpm). Aeration rate and condenser temperature used in the engineering prediction provided a practically useful estimate of evaporation; the other factors, while statistically identified as having some influence, were of negligible practical usefulness. Evaporation rates were never found to be zero, and could be at least 10% different to those expected at scale.

CONCLUSIONS

An assessment of evaporation rates for any project is encouraged, and it is recommended that the effects are accounted for by measurements, modelling or by tuning the exhaust cooling device temperature to minimize scale differences.

Peristaltic on-chip pump for tunable media circulation and whole blood perfusion in PDMS-free organ-on-chip and Organ-Disc systems

Organ-on-chip (OoC) systems have become a promising tool for personalized medicine and drug development with advantages over conventional animal models and cell assays. However, the utility of OoCs in industrial settings is still limited, as external pumps and tubing for on-chip fluid transport are dependent on error-prone, manual handling. Here, we present an on-chip pump for OoC and Organ-Disc systems, to perfuse media without external pumps or tubing. Peristaltic pumping is implemented through periodic compression of a flexible pump layer. The disc-shaped, microfluidic module contains four independent systems, each lined with endothelial cells cultured under defined, peristaltic perfusion. Both cell viability and functionality were maintained over several days shown by supernatant analysis and immunostaining. Integrated, on-disc perfusion was further used for cytokine-induced cell activation with physiologic cell responses and for whole blood perfusion assays, both demonstrating the versatility of our system for OoC applications.

Microbioreactor (micro-Matrix) potential in aerobic and anaerobic conditions with different industrially relevant microbial strains

Microscale fermentation systems are important high throughput tools in clone selection, and bioprocess set up and optimization, since they provide several parallel experiments in controlled conditions of pH, temperature, agitation, and gas flow rate. In this work we evaluated the performance of biotechnologically relevant strains with different respiratory requirements in the micro‐Matrix microbioreactor. In particular Escherichia coli K4 requires well aerated fermentation conditions to improve its native production of chondroitin‐like capsular polysaccharide, a biomedically attractive polymer. Results from batch and fed‐batch experiments demonstrated high reproducibility with those obtained on 2 L reactors, although highlighting a pronounced volume loss for longer‐term experiments. Basfia succiniciproducens and Actinobacillus succinogenes need CO₂ addition for the production of succinic acid, a building block with several industrial applications. Different CO₂ supply modes were tested for the two strains in 24 h batch experiments and results well compared with those obtained on lab‐scale bioreactors. Overall, it was demonstrated that the micro‐Matrix is a useful scale‐down tool that is suitable for growing metabolically different strains in simple batch process, however, a series of issues should still be addressed in order to fully exploit its potential.

Microwell Plate-Based Dynamic Light Scattering as a High-Throughput Characterization Tool in Biopharmaceutical Development

High-throughput light scattering instruments are widely used in screening of biopharmaceutical formulations and can be easily incorporated into processes by utilizing multi-well plate formats. High-throughput plate readers are helpful tools to assess the aggregation tendency and colloidal stability of biological drug candidates based on the diffusion self-interaction parameter (k_D). However, plate readers evoke issues about the precision and variability of determined data. In this article, we report about the statistical evaluation of intra- and inter-plate variability (384-well plates) for the k_D analysis of protein and peptide solutions. ANOVA revealed no significant differences between the runs. In conclusion, the reliability and precision of k_D was dependent on the plate position of the sample replicates and k_D value. Positive k_D values (57.0 mL/g, coefficients of variation (CV) 8.9%) showed a lower variability compared to negative k_D values (−14.8 mL/g, CV 13.4%). The variability of k_D was not reduced using more data points (120 vs. 30). A k_D analysis exclusively based on center wells showed a lower CV (<2%) compared to edge wells (5–12%) or a combination of edge and center wells (2–5%). We present plate designs for k_D analysis within the early formulation development, screening up to 20 formulations consuming less than 50 mg of active pharmaceutical ingredient (API).

[Clinical efficacy of proton pump inhibitor combined with ranitidine in the treatment of throat reflux]

Objective:To investigate the clinical effect of proton pump inhibitor combined with ranitidine on patients with laryngopharyngeal reflux. Method:Seventy patients with laryngopharyngeal reflux diagnosed in our hospital were randomly divided into group A and group B according to admission time. The difference of B symptom index, reflux symptom scale, sleep breathing test, quality of life and well-being score between the two groups were detected. Result:Before treatment, the RSI index, RFS similarity and QOLS and MUNSH scores were similar （P>0.05）. After four weeks of treatment, the group B score was 3.3±1.2, the group A score was 8.2±3.5, and the group B score was significantly lower. The RFS score of group A （6.2±2.3） was higher than that of group B （2.1±1.9, P<0.05）. The scores of QOLS and MUNSH in group B were （67.57±7.26） and （23.99±3.44）, respectively. The scores of QOLS and MUNSH in group A （50.13±10.19） and （12.21±1.47）, respectively. The results of the two groups were significantly different （P<0.05）. After treatment, the RSI index, RFS score, QOLS and MUNSH scores of the two groups were lower than those before treatment. （P<0.05）. As for the sleep respiration monitoring （PSG） results, after 4-week treatment, compared with the group A, the total sleep time of the group B was significantly increased （P<0.05）, and the number of wakefulness and wakefulness was significantly decreased. The duration of Ⅲ+Ⅳ sleep was also significantly increased, and the proportion of REM sleep time and AHI was significantly reduced （P<0.05）. Conclusion:Proton pump inhibitor combined with ranitidine is more effective and safer than single drug treatment, and can significantly improve the throat reflux symptoms.

Using a Parallel Micro-Cultivation System (Micro-Matrix) as a Process Development Tool for Cell Culture Applications

Micro-bioreactors appear frequently in today's biotechnology industry as screening and process development tools for cell culture applications. The micro-bioreactor's small volume allows for a high throughput, and when compared to other small-scale systems, such as microtiter plates, its measurement and control capabilities offer a much better insight into the bioprocess. Applikon's micro-Matrix is one of the micro-bioreactors that are commercially available today. The micro-Matrix system consists of shaken disposable 24 deep square well plates in which each well is controlled individually for pH, dissolved oxygen (DO), and temperature. Additionally, a feeding module supports automated additions of liquid to each well. This chapter describes how the micro-Matrix can be used for fed-batch cultivations of Chinese Hamster Ovary (CHO) cells.

Microbioreactors for Process Development and Cell-Based Screening Studies

Microbioreactors (MBRs) have emerged as potent cultivation devices enabling automated small-scale experiments in parallel while enhancing their cost efficiency. The widespread use of MBRs has contributed to recent advances in industrial and pharmaceutical biotechnology, and they have proved to be indispensable tools in the development of many modern bioprocesses. Being predominantly applied in early stage process development, they open up new fields of research and enhance the efficacy of biotechnological product development. Their reduced reaction volume is associated with numerous inherent advantages - particularly the possibility for enabling parallel screening operations that facilitate high-throughput cultivations with reduced sample consumption (or the use of rare and expensive educts). As a result, multiple variables can be examined in a shorter time and with a lower expense. This leads to a simultaneous acceleration of research and process development along with decreased costs.MBRs range from simple miniaturized cultivations vessels (i.e., in the milliliter scale with limited possibilities for process control) to highly complex and automated small-scale microreactors with integrated sensors that allow for comprehensive screenings in very short time or a precise reflection of large-scale cultivation conditions. Progressive developments and improvements in manufacturing and automation techniques are already helping researchers to make use of the advantages that MBRs offer. This overview of current MBR systems surveys the diverse application for microbial and mammalian cell cultivations that have been developed in recent years.

Towards the development of automated fed-batch cell culture processes at microscale

Aim: To investigate the impact of various feeding strategies on the growth and productivity of a GS-CHO cell line. Methods: Feed additions were conducted at fixed volumes or linked to a marker such as cell growth or metabolism and added as bolus or near-continuously using the automated feeding module of the micro-Matrix (Applikon). Results: The selected feeding regimens supported maximum viable cell densities of up to 1.9 × 107 cells ml−1 and final titers of up to 1.13 g l−1. Differences in growth and titer between feeding strategies were insignificant, with the exception of one feeding strategy. Conclusion: As the more complex feeding strategies did not create an advantage, the selection of a simple feeding strategy such as bolus or continuous addition of feed medium is preferred.

An Industrial Perspective on Scale-Down Challenges Using Miniaturized Bioreactors

Miniaturized stirred bioreactors (MSBRs) are gaining popularity as a cost-effective approach to scale-down experimentation. However, realizing conditions that reflect the large-scale process accurately can be challenging. This article highlights common challenges of using MSBRs for scale-down. The fundamental difference between oxygen mass transfer coefficient (k_La) and oxygen transfer rate scaling is addressed and the difficulty of achieving turbulent flow and industrially relevant tip speeds is described. More practical challenges of using MSBR systems for scale-down are also discussed, including the risk of vortex formation, changed volume dynamics, and wall growth. By highlighting these challenges, the article aims to create more awareness of these difficulties and to contribute to improved design of scale-down experiments.