Ulva spp. as a natural source of phenylalanine and tryptophan to be used as anxiolytics in fish farming

Abstract Species of the green macroalgae genus Ulva often exhibit rapid growth, are generally cosmopolitan, and are rich in amino acids, vitamins, proteins, and minerals and have high potential for commercial uses. Ulva aquaculture was established and experimentally integrated into fish and shrimp farming in Brazil as Integrated Multi-Trophic Aquaculture projects. Decreases in fish farm production are often due to deaths caused by stress – with consequent increases in production costs. Essential amino acids, such as tryptophan and phenylalanine, have been used in fish farms as anxiolytic agents. In that context, a bibliographic survey was carried out to investigate advances during the last 17 years in the use of tryptophan and phenylalanine produced by Ulva species in fish farming. The biosynthesis patterns of tryptophan and phenylalanine were also examined in the research data. References to the presence of tryptophan and phenylalanine in Ulva spp. were encountered in 32 articles, with Ulva lactuca being the species most cited. References to the use of essential amino acids as anxiolytics in fish farming were encountered in 23 articles, with tryptophan being the most cited; none of the articles, however, mentioned the use of Ulva spp. as sources of anxiolytics. Temperature and pH were the factors that most influenced phenylalanine production. In conclusion, there is a potential role for the use of selected species of Ulva in fish farming as sources of tryptophan and phenylalanine for anxiolytic purposes.