Abstract. The aim of this research was to investigate utilization of different nitrogen sources
used for the growth of microalgae and determined the optimum period of the growth. The
microalgae had been isolated previously from mangrove leaves in Banda Aceh, Indonesia and
has been identified morphologically. Three different nitrogen sources i.e., yeast extract,
monosodium glutamate or MSG and sodium nitrate were used. The biomass production was
measured by optical density using spectrophotometer. The results showed that MSG stimulated
microalgae to produce the highest amount of biomass (0.38 g/L/day) followed by yeast extract
with 0.33 g/L/day, but both were statistically not significant. Sodium nitrate developed the
lowest OD value with the amount of dried biomass only 0,16 g/L/day. Correlation analysis
indicated the yield of biomass was positively related, r = 0.953, with the optical density of the
cultures. The OD values of yeast extract, MSG and sodium nitrate cultures were 1.20, 1.18 and
0.82, respectively. The optimum time for microalgae growth was at day 9 in which 4.41 g/L of
dried biomass was accumulated in the culture where MSG was used. The maximum yield of
dried biomass for yeast extract was 4.22 g/L followed by 2.58 g/L for sodium nitrate.