Use of aluminium sulphate as flocculant for spirulina (Arthrospira platensis) with notes on the use of antioxidants for preservation under refrigerated conditions

One of the bottlenecks in microalgae harvesting is the lack of an efficient method for separating the microalgae from its culture medium. Moreover, the lack of viable and simple preservation techniques for microalgae starters hinders the immediate recovery of cultures after experiencing collapse. Hence, the present study was conducted to evaluate the use of aluminium sulphate as a flocculant for harvesting spirulina (Arthrospira platensis) and compare it with other flocculation techniques (electrolytic flocculation and autoflocculation). Moreover, the use of antioxidants to lengthen the storage of viable spirulina cells in refrigerated conditions was explored. The results of the study showed that the optimum dosage of aluminium sulphate for flocculation of spirulina is 200 ppm with 94.82 ± 0.59% efficiency in 15 – 45 minutes post-administration. Moreover, the combination of ascorbic acid and alpha-tocopherol at 0.01% v/v resulted in the highest viable cells at 57.76 ± 2.48% until the 3-week refrigeration period. This may help in maintaining viable starters. However, further investigations are needed to ascertain residuals of aluminium in harvested biomass and explore low-cost options for its reduction or removal and optimize the use of antioxidants in spirulina preservation in refrigerated conditions.