Kultivierung von extrem cyanophycinhaltigen Cyanobakterien und deren Verarbeitung zu hochpreisigen Biokunststoff-Anwendungen; Akronym: KCVB

Abstract

This research focuses on developing a sustainable method for producing cyanophycin (CPH) by cultivating and harvesting an engineered cyanobacteria strain. Cyanophycin is a biopolymer found in several cyanobacteria and some heterotrophic bacteria. It is composed of two amino acids, aspartic acid and arginine. CPH serves as a dynamic nitrogen and carbon storage, helping bacteria survive periods of limited or fluctuating nitrogen supply. CPH is of particular interest to industry due to its potential applications; however, there is currently no CPH or CPH-containing product on the market. Based on its chemical structure, we hypothesize that CPH could act as an antimicrobial agent, potentially useful in packaging perishable goods. This project aims to develop a market-ready CPH-based product prototype focused on extending the shelf life of high-value foods. To achieve this, we are targeting every aspect of the development chain, including strain and culture optimization, process upscaling, downstream processing, prototype development, and testing, alongside continuous economic viability assessments. The initial phase of the project concentrates on the cultivation and harvesting steps. Biotechnology involving cyanobacteria is often prone to contamination, a major challenge with these organisms. To avoid contamination, typically costly and time-consuming efforts are required. We developed a novel method that combines several strategies to overcome this problem. By leveraging the unique features of cyanobacteria and their partially extremophilic tendencies (such as halophilicity or alkalophilicity), we developed a continuous process with low sterility demands that runs stably for over 200 days in one trial. The principle of this method is to provide a unique environment with specific conditions that only the producer strain can tolerate. This method not only resists contamination but also maximizes CPH productivity, achieving values as high as 48% dry weight. Harvesting posed challenges due to the lack of necessary centrifuges in our facilities, where the engineered strain is cultivated. We explored flocculation to overcome this limitation. Although Al3+ was very effective, its interference during downstream processing and its low sustainability led us to explore other options. Consequently, an alternative non-Al3+ harvesting method was successfully adopted. Following the initial project phase, we produced significant amounts of biomass. CPH extraction from biomass is a well-established process optimized for laboratories. As part of the project, we are working to upscale the current extraction method to an industrial scale. We established collaborations with industrial service providers specializing in downstream processing. Through consultations, we identified several issues preventing a straightforward upscaling of the extraction process to an industrial scale. Some chemicals used are corrosive, harmful, or flammable. For example, while corrosive acids in laboratories pose no problems as glass or plastic equipment is used, large industrial facilities largely use stainless steel, which can be sensitive to these acids. Identifying these conflicts necessitated developing a new extraction method avoiding problematic substances. We started evaluating alternative processes, but since this was outside the project's scope, we could not finalize a new method during the project's duration. However, we laid the foundation for developing a scalable method by identifying nonproblematic substances. From the produced CPH, we conducted several studies to test antimicrobial activity. Native CPH showed no antimicrobial activity, but chemically modified CPH did. We observed strong growth-inhibiting activity of chemically modified cyanophycin against bacteria and some fungi. Notably, we found that chemically modified CPH inhibits the growth of two common plant-pathogenic fungi causing green mold and sour rot disease in citrus fruits. Post-harvest diseases of citrus fruits cause significant economic damage annually. In collaboration with our partners, we developed a coating for citrus fruits that reduces spoilage. We observed a ~30% decrease in molded fruits after two weeks of incubation with the coating. Techno-Economic Analysis (TEA) was performed iteratively to evaluate the process's economic feasibility using our internal automated models. Preliminary results indicate that the modeled price of CPH is below our benchmark, demonstrating its economic competitiveness. The technology under development has made significant progress in a short time, advancing from TRL2 to TRL7 in only XXX months. Through extensive research and experimentation, we have gathered a wealth of relevant data, providing a solid foundation to transition to higher TRL levels. Datei-Upload durch TIB