Biology subjects

Kehr, P.

Publications and source records attributed to Kehr, P..

2 recordsLinked to original sources

bioRxiv2026

Design and development of online pressure sensing for microbial batch cultivation

Gas production and consumption is a direct consequence of microbial activity in environmental and industrial settings. In closed batch cultivations, headspace pressure changes therefore give valuable insights into the microbial metabolism. For laboratory scale anaerobic batch cultivations, manual manometer measurements are routinely applied, as a simple and robust method, but it is labour intensive, causes disturbances in the headspace gas and temperature, leading to suboptimal growth, inhibition and noisy data. We built and tested an automated online pressure sensor for closed batch cultivations. It is designed for microbial cultivation and integrates with sterile and anaerobic cultivation workflows. The system uses an absolute pressure sensor (0-30 bar) mounted on a custom designed PCB, with a gas-tight needle mount. An ESP32 microcontroller logs pressure and temperature locally and generates a Wi-Fi access point for real-time visualization and direct CSV download through a local homepage. We detail hardware and software design decisions, assembly, and validation including long-term stability. Case studies demonstrate the applicability for: a multiphasic biogas kinetics during anaerobic digestion, capturing gas uptake dynamics and metabolic shifts during syngas fermentations and co-feeding experiments, and long-term robustness in a multi-year monitoring of a compressed-air system. More than 130 individual sensors have been deployed over 3 years in laboratories, at various academic and industrial settings. The platform provides reproducible, high-resolution pressure measurements that enable calculation of gas formation/consumption rates and improve experimental throughput without disturbing cultures. Design files, firmware, and example analysis scripts are openly available to support adoption and further development.

bioengineering↗

bioRxiv2026

Mapping metabolic phases through online pressure and backscatter rates

Microbial metabolism can be represented as an energy-conserving process (catabolism) and a biomass-forming reaction (anabolism). Anabolism is traditionally measured through the turbidity of the culture, while catabolism is often assessed by the substrates consumed or the products formed. Standard measurements of biomass and products are intrusive and disrupt cultivation and headspace composition, potentially masking important analytical parameters and interactions. Online pressure and backscatter were combined in small-scale closed batch vials to obtain undisturbed real-time measurements of catabolic and anabolic rates, enabling mapping of metabolic phases throughout an entire batch cultivation cycle. The method identified discrete metabolic phases in yeast cultivation and thermophilic syngas fermentation. In nutrient-rich yeast cultivation, five metabolic phases were characterized, covering growth-associated and non-growth-associated gas formation. In a mixed community syngas fermentation, estimates of catabolic and anabolic rates distinguished early biomass increase from minimal net pressure change from two later gas-driven phases. An initial phase with a higher growth rate, linked to carboxydotrophy, followed by a phase with slightly lower growth and increased gas consumption, corresponding to hydrogenotrophic acetogenesis. The study demonstrates that a simple, affordable experimental setup with online pressure and backscatter measurements can be used to visualize phase-plane mapping of microbial metabolism. An additional advantage is the ability to detect sequential metabolic cascades in mixed microbial communities, which is not possible with gas-sparging bioreactor studies. Using a single simple batch culture, growth and maintenance data can be obtained, even when growth is low or absent, thereby yielding parameters applicable to phenotypic characterization and dynamic metabolic modelling.

microbiology↗