Sustainable remediation of piggery wastewater using a novel mixotrophic Chlorella sorokiniana Cbeo for high value biomass production

Piggery wastewater (PW) contains high density of organic carbon (COD), nitrogen (NH₄⁺-N and TN) and phosphorous (TP), which are essential nutrients for microalgae growth. This work was attempted to use a newly isolate Chlorella sorokiniana C_beo for recovery these compounds into its biomass via mixotrophic cultivation. Critical factors including level of ammonia, C/N ratio, pH, light intensity, sterilized/unsterilized media, and indoor/outdoor cultivations affecting biomass production and nutrients removal efficiencies were investigated. Data revealed that C. sorokiniana C_beo achieved the optimal growth in the unsterilized medium at NH₄⁺-N concentration, C/N ratio, initial pH, and light intensity of 250 mg/L, 10/1, 7, and 150 μmol/m²/s, respectively. Under the optimal conditions, dry cell weight (DCW) reached the maximal level of 4.30 g/L, which was slightly higher than 4.14 g/L determined for the sterilized medium. In 30 L-scale photobioreactor, C. sorokiniana C_beo grown under indoor and outdoor achieved DCW of 3.61 and 3.19 g/L, respectively. COD, NH₄⁺-N, TN, TP removal efficiencies for both conditions were determined as 91.9–96.7, 96.6–99.7, 96.2–96.4, and 98.2–100 %, respectively. The C. sorokiniana C_beo biomass contained 14–27 % lipid, 25–32 % carbohydrate, 44–48 % protein, and 0.25–0.97 % lutein. Interestingly, α-Linolenic acid (C18:3n3) was 19.84 –27.0 % of the total fatty acids. C. sorokiniana C_beo is the promising algal strain for development of a sustainable biorefinery of PW.