# Green Macrolgae Biomass Upcycling as a Sustainable Resource for Value-Added Applications
## 4 Conclusions  
This study investigated the potential of green macroalgae _Ulva flexuosa_ aquaculture by-product biomass as a sustainable and valuable natural resource. This work contributes to a better understanding of macroalgae biochemical composition and bioactive properties and provides insights for optimizing cultivation and extraction strategies, with particular emphasis on species from Northeast Brazil. Our findings revealed significant concentrations of chlorophylls and carotenoids in the green macroalgae biomass, as well as their notable antioxidant capacity. When the bioactivity of different _Ulva flexuosa_ extracts was investigated, a clear influence of the type of solvent used was observed. While methanol and ethanol extracts had higher flavonoid concentration and better performance on antioxidant assays, water extracts had higher total phenolic concentration. Taking altogether, our findings highlight the potential of _Ulva flexuosa_ as a source of essential nutrients, such as minerals, fibers, essential fatty acids, and bioactive compounds for multiple applications. However, one important limitation is that the bioactivity was determined using in vitro assays, which may not fully reflect their effectiveness or safety for in vivo systems. Further research is needed on isolating and characterizing individual compounds and evaluating their potential applications in food, pharmaceutical, and cosmetic formulations. Moreover, the investigation of heavy metals and microbial contaminants is warranted for safety purposes. It is also worth noting that, while ethanol is considered a safe and sustainable solvent for food applications, methanol is not approved for such use due to its toxicity. Therefore, future research should consider the use of food-grade and environmentally friendly solvents. Lastly, future studies should explore sensory acceptance and compliance with food regulations to support the effective incorporation of _Ulva flexuosa_-based ingredients into products. By advancing knowledge in this field, we will be able to address food challenges and contribute to sustainable marine resource utilization, which aligns with global efforts to develop high-quality alternative products using environmentally friendly practices. Conceptualization, A.T.d.M.F., K.N.M., M.R.d.S.P. and R.T.H. ; methodology, A.T.d.M.F. ; formal analysis, A.T.d.M.F., A.S.L.d.L., E.M.d.O.P., L.D.S.F., R.B.L.d.C., A.R.d.A. and F.A.S.D.P. ; data curation, A.T.d.M.F. and A.S.L.d.L. ; writing--original draft preparation, A.T.d.M.F. ; writing--review and editing, A.T.d.M.F., K.N.M. and R.T.H. ; supervision, M.R.d.S.P, K.N.M. and R.T.H. All authors have read and agreed to the published version of the manuscript. This study was financed in part by the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior--Brasil (CAPES, Brazil)--Finance Code 001 (process 88887.912319/2023-00). Not applicable. The raw data supporting the conclusions of this article will be made available by the authors on request. The authors are grateful to UFRN and LEA (Food Engineering Laboratory) for supporting this research. The authors would like to thank the company PRIMAR AQUACULTURE for the kind donation of the green algae biomass used in this study. The authors declare no conflicts of interest. The following abbreviations are used in this manuscript: