Integrated utilization of microalgae cultured in aquaculture wastewater: wastewater treatment and production of valuable fatty acids and tocopherols

Abstract

Microalgal cultivation in aquaculture wastewater (AWW) from recirculating aquaculture systems (RAS) is an approach for combined production of valuable algal biomass and AWW treatment. The growth, nutrient uptake, fatty acid (FA) profile, and tocopherol content of mixed algal cultures of Euglena gracilis with Selenastrum grown in AWWs from pikeperch (Sander lucioperca) and catfish (Clarias anguillaris) RAS were studied. The highest algal biomass (1.5 g L −1), lipid (84.9 mg L −1), and tocopherol (877.2 μg L −1) yields were achieved in sludge-amended pike perch AWW. Nutrient removal rates in experiments were 98.9-99.5 and 98.4-99.8% for NH 4-N and PO 4-P, and 75.4-89.2% and 84.3-95.7% for TN and TP, respectively, whereas the COD was reduced by 45.8-67.6%. Biomass EPA and DHA content met, while ARA and tocopherol content exceeded the requirements for fish feed. Algal cultivation in AWWs is a promising alternative for AWW treatment while providing a replacement for fish oil in feed.

Production of Microalgal Biomass Using Aquaculture Wastewater as Growth Medium

“…In the studies carried out by Halfhide et al [35] a maximum mean biomass concentration for Scenedesmus (0.41 g/L) in the tilapia RAS wastewater was achieved after 36 h. The high contents of nitrogen and phosphorus in wastewater are reported to promote the production of microalgal biomass, with the proportion of these components playing an important role [30]. In the studies conducted by Tossavainen et al [36], the largest content of mixed biomass of Euglena gracilis and Selenastrum (1.5 g/L) was observed in the wastewater obtained from pikeperch aquaculture, in which the contents of nitrogen and phosphorus were 34.4 and 6.1 mg/L, respectively. In the sewage wastewater obtained from catfish aquaculture, where the content of biogen was much lower (23.7 mg/L of N and 3.6 mg/L of P), the amount of biomass determined was only 0.08 g/L, and the N/P value of the algal biomass was N15/P1.…”

“…Water 2020, 12, x FOR PEER REVIEW 7 of 11 role [30]. In the studies conducted by Tossavainen et al [36], the largest content of mixed biomass of Euglena gracilis and Selenastrum (1.5 g/L) was observed in the wastewater obtained from pikeperch aquaculture, in which the contents of nitrogen and phosphorus were 34.4 and 6.1 mg/L, respectively. In the sewage wastewater obtained from catfish aquaculture, where the content of biogen was much lower (23.7 mg/L of N and 3.6 mg/L of P), the amount of biomass determined was only 0.08 g/L, and the N/P value of the algal biomass was N15/P1.…”

Nutritional evaluation of two marine microalgae as feedstock for aquafeed

“…The requirement of an EAA or EFA (essential fatty acid) for aquatic animals such as shrimp is not as easily incorporated into feed as its corresponding amino acid or fatty acid because crystalline amino acids or fatty acids sometimes cannot be effectively utilized (Chen, Leu, & Roelants, 1992). Most current research on microalgae-based fodder has focused only on either proteins or lipids (rarely both) (Lim, Jeong, Kim, & Ok, 2018;Tibbetts et al, 2017;Tossavainen et al, 2019). Most current research on microalgae-based fodder has focused only on either proteins or lipids (rarely both) (Lim, Jeong, Kim, & Ok, 2018;Tibbetts et al, 2017;Tossavainen et al, 2019).…”

“…More attention has been drawn to those 'essential' ingredients in diets by neglecting other 'non-essential' ones such as short-chain fatty acids (SCFAs) (Cho et al, 2015;Marchetti et al, 2018;Tossavainen et al, 2019;Wang, Sheng, & Yang, 2017). More attention has been drawn to those 'essential' ingredients in diets by neglecting other 'non-essential' ones such as short-chain fatty acids (SCFAs) (Cho et al, 2015;Marchetti et al, 2018;Tossavainen et al, 2019;Wang, Sheng, & Yang, 2017).…”

“…Nevertheless, even in these studies, such evaluation occurs with some biases. More attention has been drawn to those 'essential' ingredients in diets by neglecting other 'non-essential' ones such as short-chain fatty acids (SCFAs) (Cho et al, 2015;Marchetti et al, 2018;Tossavainen et al, 2019;Wang, Sheng, & Yang, 2017).…”