Nutrient starvation and light deprivation effects on starch accumulation in Landoltia punctata cultivated on anaerobically digested dairy manure

Abstract

Duckweed has been recognized for its potential of producing biomass on nutrients from waste streams. Our research has shown that strains of duckweed can be successfully cultivated on anaerobically digested (AD) dairy manure under controlled levels of nitrogen (N) and phosphorus (P). The objective of this study was to explore the maximization of starch accumulation in Landoltia punctata (Mey.) Les & Crawford strain 0128 under different cultivation conditions using AD dairy manure as the nutrient source. Experimental results have shown that the most influential factors for starch accumulation in L. punctata were the nutrient concentration and the appropriate scheduling of nutrient starvation at the right growth stages. In our study, nutrient starvation for starch accumulation in L. punctata was achieved by incorporating nutrient addition of appropriately diluted AD dairy manure sequentially in a controlled manner under a constant light intensity of 3,000 lx. It was observed that a starch concentration of 30% (w/w) within the L. punctata biomass was achieved with an initial total N of 57.1mg L-1 and a total P of 6.7mg L-1 after a 30-d cultivation. Under the abovementioned cultivation conditions, the duckweed L. punctata recovered 16.3% (±4.0%) of total N and 25.9% (±6.6%) of total P from AD manure into its biomass. It is concluded that L. punctata can be successfully cultivated on nutrients from dairy manure for starch production, which would achieve well-being for dairy farmers by producing a feedstock for biofuels while treating dairy wastewater in an environmentally friendly manner.