Production of aquatic feed grade algal powder from turtle breeding wastewater using a locally isolated Spirulina sp. JXSC-S1

Spirulina sp. JXSC-S1 was isolated from a local turtle breeding wastewater storage pool in Jiaxing City, Zhejiang Province, China. Morphological studies revealed that the color, shape, spiral pitch, spiral wide and cell size of the strain fits the typical morphological characteristics of Spirulina platensis. Growth dynamics of the strain were studied in both Zarrouk medium and turtle breeding wastewater (TBW), and were compared with three S. platensis strains S6, S2 and Ns-90020 that are applied in large-scale Spirulina culturing in China. All strains grew well in Zarrouk medium. The strain JXSC-S1 demonstrated a growth rate of 1.64 day-1, similar to the growth rates of S. platensis S6 and S2 and faster than S. platensis Ns-90020. When the culturing medium was changed to TBW, all the strains except the strain JXSC-S1 grew much slower than in Zarrouk meidum. By means of continuous TBW cultivation, the biomass yield of Spirulina sp. JXSC-S1 was up to 24±9 g·m-2·day-1 in dry weight, with 59.10±3.48% of crude protein in dry mass, meeting the Chinese Spirulina Standard for Animal Feed (GB/T 17423-1998). This study shows that Spirulina sp. JXSC-S1 can be used for production of aquatic protein feed by recycling nitrogen and phosphorus from TBW.