Composition and nutritive value of sewage-grown duckweed (Lemna minor L.) for rats

Gross composition and carotenoid and heavy metal content of sewage-grown duckweed were analysed. The essential amino acid pattern of its protein was also determined. The dry matter content in fresh duckweed when harvested ranged from 78 to 95 g per kg. Gross composition of duckweed grown at the sewage inlet and water outlet did not differ markedly but the former contained about 30% more carotenoid. The protein content of both samples exceeded 300 g per kg (dry matter basis). This protein was high in lysine but low in sulphur amino acids. The metal (zinc, copper, lead and cadmium) content was below harmful levels. tritive value of protein of duckweed grown at the sewage inlet, determined on rats using the Thomas-Mitchell balance method, was higher (33) than when grown at the water outlet (25). The true digestibility of both proteins was relatively low (60% and 51%, respectively).