Duckweed biorefinery – Potential to remediate dairy wastewater in integration with microbial protein production

Abstract

The phytoremediation potential of Duckweed in treating dairy wastewater (DWW) was studied, focusing on its utilization as nutritional biomass. The process resulted in good treatment efficiency with removal of organic carbon of 74% (COD), nitrates of 66% and phosphates of 80%. The increase in duckweed fronds with time was observed (doubling time (DT) - 0.87) resulting in an overall dry weight of 3.73 g. The lentils showed 58% of protein, 29.5% of carbohydrate (with 20% of starch), 15.6% of lipid (FAME-29.3%-saturated, 40.7%-mono- and 30%-poly-unsaturated fatty acids) and good amino acid content (34.04% essential and 65.92% non-essential). The biomass hydrolysate (mild acid pretreated) served as a substrate for microbial protein (MP) production using Bacillus subtilis, resulting in 60% of protein (0.57 g protein/g COD consumed; 0.63 g protein/g N consumed) and 21% of carbohydrate. The duckweed biomass offers multiple benefits including nutritional supplement in food/feed for livestock and poultry industries along with concurrent wastewater treatment as well serves as potential feedstock for biorefinery.