Commercial raw materials from algaculture and natural stocks of Ulva spp.

Ulva species have potential uses in several industrial sectors as they are rich in proteins, vitamins, fibers, and minerals. They also produce the essential amino acid tryptophan, which can act as an anxiolytic. With the increasing use of bioactive compounds obtained from algal species for commercial purposes, it will be necessary to evaluate the best methods for obtaining them, whether harvesting from natural beds or seaweed cultivation. Aquaculture has been indicated as an alternative method of acquiring algal biomass that avoids the harvesting and depredation of natural beds. To assess the feasibility of harvesting natural stocks of Ulva spp. (U. lactuca and U. flexuosa), algal biomass and relative species abundances were quantified at three sites in southeastern Brazil during 14 sampling periods. The results of those field biomass analyses allowed us to estimate their annual productions and compare them with projected productions of Ulva spp. under algaculture conditions. Tryptophan production by cultivated U. lactuca (as a high value-added product) was compared with the tryptophan concentrations of Ulva spp. from natural beds. No consistent patterns of total biomass production or relative abundances of the Ulva spp. were obtained during the sampling periods, making it impossible to accurately estimate sustainable biomass production for commercial uses. We diagnosed greater production sustainability in algaculture than in algal beds. The concentration of tryptophan produced by U. lactuca in algaculture was 60% higher than that from natural stocks. Tryptophan was quantified for the first time here in U. flexuosa.