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- Drying microalgae using an industrial solar dryer: a biomass quality assessmentPublication . Schmid, Benjamin; Navalho, Sofia; Schulze, Peter S.C.; Van De Walle, Simon; Van Royen, Geert; Schüler, Lisa M.; Maia, Inês Beatriz; Bastos, Carolina; Baune, Marie-Christin; Januschewski, Edwin; Coelho, Ana; Pereira, Hugo; Varela, João; Navalho, João; Rodrigues, Alexandre Miguel CavacoMicroalgae are considered a promising resource of proteins, lipids, carbohydrates, and other functional biomolecules for food and feed markets. Competitive drying solutions are required to meet future demands for high-quality algal biomass while ensuring proper preservation at reduced costs. Since often used drying methods, such as freeze or spray drying, are energy and time consuming, more sustainable processes remain to be developed. This study tested an indirect and hybrid solar dryer as an alternative to conventional freeze drying of industrially produced Tetraselmis chui and Nannochloropsis oceanica wet paste. The effects of the drying method on biomass quality parameters, including biochemical profiles, functional properties, and microbial safety, were assessed. No significant differences were found between the applied drying technologies for total proteins, carbohydrates, lipids, and fatty acid profiles. On the other hand, some pigments showed significant differences, displaying up to 44.5% higher contents in freeze-dried samples. Minor differences were also registered in the mineral profiles (<10%). Analyses of microbial safety and functional properties of the solar-dried biomass appear adequate for food and feed products. In conclusion, industrial solar drying is a sustainable technology with a high potential to preserve high-quality microalgal biomass for various markets at expected lower costs.
- Bioremediation of drainwater from soilless cultivation by Tetradesmus obliquus and Raphidonema monicae: growth performance and biochemical composition from lab to industrial scalePublication . Maia, Inês Beatriz; Pinto, Bruno; Carneiro, Mariana; Konucu, Merve; Schulze, Peter S.C.; Santos, Tamara; Rodrigues, Alexandre M.C.; Esteves Lopes Navalho, João Carlos; Costa, Monya; Pereira, Hugo; Varela, JoãoTo meet the demands of the growing population, agricultural practices have been increasing and putting a strain on land and freshwater usage. Soilless agriculture has emerged as a more sustainable practice to mitigate this issue but still generates nutrient-rich drainwater that can harm the environment if not properly managed. In this context, this study explores a circular economy approach to reuse the drainwater of soilless farming as a culture medium for microalgae production. For this, the growth performance of four strains, Chlorella sp., Nannochloropsis limnetica, Raphidonema monicae and Tetradesmus obliquus, was assessed using drainwater under summer and winter conditions at lab-scale. Based on productivity, protein and polyunsaturated fatty acids (PUFA) contents, T. obliquus and R. monicae were selected for comparison in pilot-scale flat-panel photobioreactors (FP-PBR) and raceway ponds (RW). T. obliquus presented significantly higher growth in FP-PBR (0.11 g L-1 d(-1)) compared to RW (0.09 g L-1 d(-1)), with complete nitrate removal in both systems. R. monicae showed similar growth across systems, removing 19 % of nitrate in FP-PBR and 56 % in RW. Principal component analysis indicated species-specific traits drive biochemical profiles, with limited influence from the cultivation system. Both species were cultivated in 19-m(3) tubular photobioreactors, with improved productivities (T. obliquus with 0.23 g L-1 d(-1) and R. monicae with 0.13 g L-1 d(-1)) until stationary phase or legal nitrate limits, yielding about 20 kg of dry weight each. The biomass produced in drainwater was biochemically characterized, showing it was rich in proteins (>30 %), PUFA (>55 %) and phenolics, highlighting their potential application in various sectors, including aquaculture and agriculture. Overall, this study demonstrates the potential of these strains for drainwater treatment, promoting a circular economy by converting waste into valuable biomass.
- Tailored bacterial co-cultures improve Tisochrysis lutea growth and nutrient profiles under xenic conditions: a new pathway to improve microalgal productionPublication . Santos, Tamara; da Fonseca Simões, Beatriz; Rossetto, Veronica; Pereira, Hugo; Maia, Inês Beatriz; Oliveira, Marta; Esteves Lopes Navalho, João Carlos; Engelen, Aschwin; Varela, JoãoThe marine haptophyte Tisochrysis lutea is a valuable source of high-value compounds, including polyunsaturated fatty acids like docosahexaenoic acid, and pigments (e.g., fucoxanthin). However, high production costs and variability remain major challenges for its large-scale application in aquaculture, pharmaceuticals, and biotechnology industries. Therefore, strategies to enhance biomass production and quality are actively explored. In natural environments, T. lutea establishes mutualistic interactions with bacteria to obtain essential nutrients such as vitamin B12, yet the role of bacteria in industrial cultures remains poorly understood. In this study, 145 bacterial strains were isolated and taxonomically identified from industrial T. lutea cultures, with members of the class Gammaproteobacteria and Actinomycetia being the most prevalent. Forty isolates were screened individually in co-culture with T. lutea revealing strain-specific effects on growth and biochemical composition. Seven beneficial strains were used to design 21 tailored bacterial blends. Several consortia enhanced biomass production (up to 74 %) and increased key bioactive compounds, particularly methylcobalamin (up to 300 %). These findings demonstrate the potential of tailored bacterial consortia to enhance T. lutea productivity and nutritional quality under production-relevant xenic conditions, enabling strategic microbiome modulation for specific industrial goals.