Optimizing crude protein production from minute duckweed (Lemna perpusilla Torr) grown in varied NPK based medium

Abstract

A suitable growth medium has to be developed to implement the potential use of minute duckweed (L. perpusilla Torr.). This tiny floating aquatic plant has been widely promoted as a source of protein. This research aims to find the optimal NPK based media for enhancing plant protein productivity. The duckweed was grown in twelve various NPK based media formulations (respectively named as Box-A to box-L, each has a surface area of 0.0945 m2), and the crude protein productivity was examined. Determination of crude protein through the total biomass nitrogen (TN) analysis was performed using the modified Salicylic acid method, which combined alkaline persulphate digestion before the absorbance measurement with a UV-Vis spectrophotometer. The highest crude protein productivity in dry weight was 18.02 mg/m2.day or estimated equal to 65.76 kg/ha/year found on the Box D (consisted of blending Terminalia catappa leaf extract as bioalgacide agent and trace elements in NPK of 100 mg/L). Meanwhile, the highest Total Nitrogen removal (98.6%) was observed on box F (mixed of NPK 100 mg/L, Terminalia catappa leaf extract, trace elements, and molasses solutions). The alternative formulation was blending NPK 300 mg/L with trace element (box L) that enable to yield of crude protein as much as 30.97 mg/m2.day or estimated equal to 113.04 kg/ha.year. These findings proved that duckweed biomass could be potentially used as a protein source material and improve water quality in aquaculture. Further, the use of three-dimensional models to demonstrate the effect of the remaining concentration of TN and TP in medium against crude protein content in the biomass was also discussed.