Open Access

This study presents a laboratory proof-of-concept for a novel scattering-based fiber-optic sensor for continuous in situ monitoring of free NH3 in highly loaded aqueous bioprocess media. The sensing element consists of a thin phenyl-modified sol–gel coating with covalently immobilized bromocresol green on fused silica fiber rods. The experimental observations are consistent with covalent immobilization of the dye within the hybrid matrix, which appears to suppress classical pH-dependent indicator behavior and enables a largely pH-independent response within the biogas-relevant range of 6.8–8.5. Nanoscale structural inhomogeneities within the high-refractive-index sol–gel layer are expected to contribute to weak light scattering and to enhance the effective optical interaction length. Upon exposure to free NH3, the sensor shows reversible spectral changes, with the strongest response observed at 748 nm. The sensor exhibited an exponentially saturating calibration behavior between 20 and 200 mg/L free NH3 at 24 °C, response times of t90 less than 2 min, and good reversibility over more than 50 cycles. The deliberately minimalist optical setup consists of a white LED, the coated fiber element, and a compact spectrometer. It operated at low power without reagents, membranes, or consumables and achieved an AGREE greenness score of 0.88. Preliminary tests in real biogas digestate suggest promising matrix compatibility for continuous in situ monitoring in anaerobic digestion and related nitrogen-rich bioprocesses.

Electrospinning is a versatile technique for producing polymer nanofibers with high ratios of surface area to volume and tunable porosity. Conventional approach to the optimization of processing parameters such as voltage and flow rate frequently encounters limitations in reproducibility and scalability. This review proposes a comprehensive framework that integrates macromolecular design principles with established electrohydrodynamic theories. We analyze how intrinsic molecular traits, specifically chain entanglement density, molecular weight distribution (MWD), topological architecture, and polymer–solvent thermodynamic interactions, define the boundaries of jet stability and solidification. Key findings highlight that while molecular weight establishes a baseline for spinnability, the MWD dictates the dynamic response under extreme deformation. Notably, high-molecular-weight fractions act as elastic load-bearers that suppress capillary breakup. Furthermore, we discuss here how molecular architecture and solvent-mediated segmental mobility determine whether molecular orientation is kinetically trapped or relaxed during the nanosecond timescales of jet flight. By establishing a hierarchical design logic prioritizing molecular and formulation variables over processing parameters, this framework provides a robust strategy to overcome challenges in scalability and reproducibility, positioning electrospinning as a sensitive probe for macromolecular dynamics under extreme elongation.

This study presents a new mathematical model for determining the specific growth rate of biomass in biotechnological production processes, which aims to optimize the production of biotechnological products such as the advanced material polyhydroxyalkanoates. The specific growth rate is classified by the FDA as a critical process parameter that affects product quality and quantity, but is difficult for laboratory personnel to determine. Therefore, a simple and robust method for real-time monitoring and control is crucial. According to the current state of the art, the established Luedeking-Piret model for determining the specific growth rate requires the determination of the biomass as an absolute value to initialize the model and to determine two further model parameters. However, determining the biomass is time-consuming and error-prone. The new relative model replaces this value with the relative change in biomass, which can be easily recorded using standard laboratory methods such as optical density measurement. This eliminates the need for time-consuming and resource-intensive preliminary work. Despite this simplification, simulation tests have shown that the new model delivers identical results to the established model. It represents an independent, precise alternative and offers advantages in terms of handling. The results underline the model’s potential to make bioprocesses more sustainable and efficient. Especially in research, material consumption, laboratory time and costs can be reduced compared to the established model. Future experiments will further investigate the performance of the new approach compared to the established model.

Bioreactor systems for cultivating cells in Life Sciences have been widely used for decades. Recently, there is a trend towards miniaturization, disposables and even micro platforms that fulfill increasing demands strongly aiming for production and testing of novel pharmaceutical products. Miniaturized bioreactors allow low power consumption, portability and reduced space requirements and utilize smaller volumes of reagents and samples [1,2]. A recursive strategy is necessary for optimizing the design and the manufacture of such miniaturized bioreactors. For the fabrication of these prototypes utilized micro-milling. Micro milling is a mechanical process which is commonly applied to create micro-structures in metals, e.g. aluminum and steel, or polymers, e.g. poly carbonate substrates. The structures and geometries are generated by utilizing computer aided design. By means of computer-aided manufacturing, the machining operations are implemented and then transferred to the machine tool. The machine tool moves the cutting tools with certain speeds, feeds and traverse ranges to the substrate. Micro milling has the advantage that the materials are generally not degraded by chemical substances, heating procedures or electromagnetic radiation.

Three building blocks have been designed to chemically link to a gold surface and vertically self-assemble through thymine–adenine hydrogen bonds. Starting from these building blocks, two different films were engineered on gold surface. Film 1 consists of adenine linked to lipoic acid (Lipo–A) to covalently bind to the gold surface, and ZnTPP linked to a thymine (T–ZnTPP). Film 2 has an additional noncovalently linked layer: a helical undecapeptide analogue of the trichogin GA IV peptide, in which four glycines were replaced by four lysines to favor a helical conformation and reduce flexibility and the two extremities were functionalized with thymine and adenine to enable Lipo–A and T–ZnTPP binding, respectively. These films were characterized by electrochemical and spectroscopic techniques, and were very stable over time and when in contact with solution. Under illumination, they could generate current with higher efficiency than similar previously described systems.