Heliyon (Feb 2024)
Potential of Synechococcus elongatus UTEX 2973 as a feedstock for sugar production during mixed aquaculture and swine wastewater bioremediation
Abstract
The demand for protein is increasing with an expanding world population and is influencing the rapid growth of fish and animal agriculture. These sectors are becoming a significant source of water pollution and need to develop environmentally sustainable techniques that are cost-effective, ideally with potential for downstream value-added production. This study investigated the potential of one of the fastest-growing cyanobacterial species, Synechococcus elongatus UTEX 2973, for bioremediation of mixed wastewater (combination of sturgeon and swine wastewater). Three different mixing ratios (25:75, 50:50, and 75:25 sturgeon:swine) were compared to find a suitable combination for the growth of S. elongatus as well as carbohydrate accumulation in biomass. The final biomass production was found to be 0.65 ± 0.03 g Dry cell Weight (DW)/L for 75%–25 %, 0.90 ± 0.004 g DW/L for 50%–50 %, and 0.71 ± 0.04 g DW/L for 25%–75 % sturgeon-swine wastewater combination. Cyanobacteria cultivated in 50%–50 % sturgeon-swine wastewater also accumulated 70 % total carbohydrate of DW, whereas 75%–25 % sturgeon-swine and 25%–75 % sturgeon-swine accumulated 53 % and 45 %, respectively. Subsequently, the S. elongatus cells were grown in a separate batch of 50%–50 % sturgeon-swine wastewater and compared with cells grown in BG11 synthetic growth media. Cultivation in BG11 resulted in higher biomass production but lower carbohydrate accumulation than 50%–50 % mixed wastewater. Final biomass production was 0.85 ± 0.08 g DW/L for BG11 and 0.65 ± 0.04 g DW/L for 50%–50 % sturgeon-swine wastewater. Total carbohydrate accumulated was 75 % and 64 % of DW for 50%–50 % sturgeon-swine mixed wastewater and BG11 growth media, respectively, where glycogen was the main carbohydrate component (90 %). The nutrient removal efficiencies of S. elongatus were 67.15 % for orthophosphate, 93.39 % for nitrate-nitrite, and 97.98 % for ammonia. This study suggested that S. elongatus is a promising candidate for enabling simultaneous bioremediation of mixed wastewater and the production of value-added biochemicals.
