Effect of various phosphate fertilizers on growth and antioxidant activity of Euglena gracilis Klebs, 1883 IDN22 isolated from Dieng Peatland, Indonesia

Abstract

Importance of the work: A cost-efficient, phosphate fertilizer-based medium could improve
the economic feasibility of Euglena gracilis Klebs, 1883 production for food industry applications.
Objectives: To assess the effect of different phosphate fertilizer types on the growth and
antioxidant activity of the indigenous isolate E. gracilis IDN22.
Materials and Methods: Batch cultivation (150 L) of the local isolate E. gracilis IDN22
was conducted in separate tanks for each treatment, using media supplemented with
various phosphate fertilizers: triple super phosphate (TSP), diammonium phosphate (DAP),
monoammonium phosphate (MAP) and fused magnesium phosphate (FMP). Technical
replicates (n = 3) were collected for the analysis. The observed variables were: cell growth
(measured using a Neubauer counting chamber); biomass production (using the filtration
method); pigment concentration and productivity (analyzed using spectrophotometry);
and antioxidant activity (assessed using the 2,2 diphenyl-1-picrylhydrazyl method based on
half maximal inhibitory concentration (IC50) values).
Results: The DAP treatment produced the highest cell density in the exponential phase on
day 13, while the MKP treatment had the highest growth rate (µmax = 0.736). In contrast,
the FMP treatment had the highest values for biomass content, pigment productivity
and absolute pigment. In addition, the MKP treatment had the highest antioxidant activity
(IC50 = 4.172 mg/mL), while FMP had the lowest antioxidant activity (IC50 = 12.647 mg/mL).
Main finding: The findings offer a scientific basis for selecting fertilizers that support
sustainable and efficient microalgae production for food industry applications.