Cyanobacteria are ubiquitous phototrophic prokaryotes that find a wide range of applications in industry due to their broad product spectrum. In this context, the application of cyanobacteria as biofertilizers and thus as an alternative to artificial fertilizers has emerged in recent decades. The benefit is mostly based on the ability of cyanobacteria to fix elemental nitrogen and make it available to the plants in a usable form. However, the positive effects of co-cultivating plants with cyanobacteria are not limited to the provision of nitrogen. Cyanobacteria produce numerous secondary metabolites that can be useful for plants, for example, they can have growth-promoting effects or increase resistance to plant diseases. The effects of biotic and abiotic stress can as well be reduced by many secondary metabolites. Furthermore, the biofilms formed by the cyanobacteria can lead to improved soil conditions, such as increased water retention capacity. To exchange the substances mentioned, cyanobacteria form symbioses with plants, whereby the strength of the symbiosis depends on both partners, and not every plant can form symbiosis with every cyanobacterium. Not only the plants in symbiosis benefit from the cyanobacteria, but also vice versa. This review summarizes the beneficial effects of cyanobacterial co-cultivation on plants, highlighting the substances exchanged and the strength of cyanobacterial symbioses with plants. A detailed explanation of the mechanism of nitrogen fixation in cyanobacterial heterocysts is given. Finally, a summary of possible applications of co-cultivation in the (agrar-)industry is given.

Phototrophic biofilms, in particular terrestrial cyanobacteria, offer a variety of biotechnologically interesting products such as natural dyes, antibiotics or dietary supplements. However, phototrophic biofilms are difficult to cultivate in submerged bioreactors. A new generation of biofilm photobioreactors imitates the natural habitat resulting in higher productivity. In this work, an aerosol-based photobioreactor is presented that was characterized for the cultivation of phototrophic biofilms. Experiments and simulation of aerosol distribution showed a uniform aerosol supply to biofilms. Compared to previous prototypes, the growth of the terrestrial cyanobacterium Nostoc sp. could be almost tripled. Different surfaces for biofilm growth were investigated regarding hydrophobicity, contact angle, light- and temperature distribution. Further, the results were successfully simulated. Finally, the growth of Nostoc sp. was investigated on different surfaces and the biofilm thickness was measured noninvasively using optical coherence tomography. It could be shown that the cultivation surface had no influence on biomass production, but did affect biofilm thickness.

The interdisciplinary nature of science, technology, engineering, and mathematics (STEM) offers the opportunity to implement educational approaches to biotechnology and process engineering issues. The focus should be on the promotion of scientific literacy in contexts relevant to research, industry, and society. This article specifically shows the development of suitable low-level experiments to provide a milestone for the implementation of biotechnological and process engineering issues in STEM education. The experiments show the successful transfer of inquiry-based bioprocess engineering experiments with a Do-It-Yourself (DIY) bioreactor and low-cost sensors. It was possible to achieve comparable trends of process-relevant state variables like mixing time and volumetric mass transfer coefficient (k_La) for the DIY bioreactor in comparison to established commercial systems. Furthermore, microalga Microchloropsis gaditana could be successfully cultivated under different cultivation conditions in the DIY system, and the respective growth curves could be observed. The DIY system is well suited for experimental application in schools and provides a scientifically substantiated basis for data interpretation. The scientific outreach approach and cooperation in a multiprofessional team for the transfer of process engineering questions to education can be evaluated as enriching. Experiments involving educational concepts offer a variety of connecting elements in the curriculum and opportunities to foster scientific literacy.

Cyanobacteria are promising organisms for the sustainable production of various biotechnological interesting products. Due to their energy production via photosynthesis, the cultivation of cyanobacteria expands the CO₂ cycle. Most cyanobacteria form biofilms on surfaces in their natural environment by surrounding the cells with a self-produced matrix of extracellular polymeric substances (EPS) that hold the cells together. These special growth properties need special reactors for cultivation. By immobilizing cyanobacteria on carriers, systems currently established in industry could also be used for biofilm formers. Various artificial carriers for immobilized growth of cyanobacteria and microalgae have already been described in the literature. However, the use of waste materials or natural biodegradable carriers would be more sustainable and is, therefore, the focus of this study. Dried Luffa cylindrica, zeolite, and corn stalks were investigated for their use as carriers for cyanobacteria. L. cylindrica was shown to be an excellent natural carrier for (i) Anabaena cylindrica, (ii) Nostoc muscorum 1453-12a, and (iii) Nostoc muscorum 1453-12b. Higher or at least similar growth rates were achieved when cyanobacteria were cultivated with L. cylindrica compared to submerged cultivation. Additionally, the production of EPS and C-phycocyanin was increased at least 1.4 fold in all strains by culturing on L. cylindrica. The improved growth could be explained on the one hand by the high surface area of L. cylindrica and its properties, and, on the other hand, by the release of growth-promoting nutrients from L. cylindrica to the medium.

Cyanobacteria are promising organisms for sustainable biotechnology due to their ability to grow photoautotrophically and their wide range of products. Many cyanobacteria grow in the form of biofilms, which is why the development of photobioreactors (PBR) for the cultivation of cyanobacteria in the form of biofilms is of great interest. However, these biofilm PBR are mostly based on artificial growth surfaces, whereas biodegradable growth surfaces would be favored in terms of sustainable production and application. Luffa sponges (the dried fruit of Luffa cylindrica) are excellent biodegradable growth surfaces for cyanobacteria. Therefore, a biofilm PBR for cultivation of cyanobacteria on Luffa was developed in this study. Since many cyanobacteria grow naturally as biofilms in an air‐exposed form and this should be imitated to improve growth, an aerosol‐based PBR (abPBR) should be used for cultivation. This involves supplying the cyanobacteria with a nutrient mist. The abPBR was comprehensively characterized by determining the distribution of light, humidity and temperature inside the reactor. In addition, the residence time distribution of the aerosol was determined both experimentally and simulatively. In final cultivation experiments, it was shown that the abPBR is ideal for cultivating cyanobacteria and at the same time the aerosol system enables a simple imitation of drought stress. With the cyanobacteria Nostoc spec. and Desmonostoc muscorum, maximum area‐time‐yields (ATY) in relation to the growth surface of 6.34 and 4.19 g m⁻² d⁻¹, respectively, were achieved. Compared to previously developed abPBR, the ATY has been increased by a factor of 2.3.