Agar extraction and purification of R-phycoerythrin from Gracilaria tenuistipitata, and subsequent wastewater treatment by Ulva prolifera

This study investigated the large-scale use of the red macroalga Gracilaria tenuistipitata to extract partially purified R-phycoerythrin in combination with the sequential extraction of agar. The main objective was to investigate the purification of R-PE, the extraction of agar and treatment of wastewater from the whole extraction process using the green macroalga Ulva prolifera. Results showed that the processing of 1 kg fresh biomass of G. tenuistipitata yielded a 30.34 μg/g R-phycoerythrin (purification ratio > 4) with 13.83% extraction efficiency. Initial phycobiliprotein extraction had no effect on the agar yield. The physicochemical properties of the agar had industrial applications. This method of extraction reduced the water volume and alkali requirement compared with that from direct extraction from algae. In addition, the removal rates (mean ± standard deviation) from wastewater of BOD, COD, total nitrogen, inorganic nitrogen, ammonia nitrogen, nitrate, nitrite, total phosphorus and inorganic phosphorus were 28.34 ± 0.10%, 23.50 ± 3.47%, 45.59 ± 6.31%, 63.82 ± 2.94%, 40.77 ± 0.95%, 74.06 ± 5.63%, 70.37 ± 2.59%, 65.26 ± 5.77%, and 72.40 ± 5.43% after the treatment with 2 days respectively. This extraction and subsequently eco-friendly wastewater treatment method could have practical application in the agar industry.