Characterization of Growth and Protein Contents from Microalgae Navicula incerta with the Investigation of Antioxidant Activity of Enzymatic Hydrolysates

Microalgae are major primary producers of organic matters in aquatic environments through their photosynthetic activities. Benthic diatom Navicula incerta is the major component of phytoplankton and also relatively easy to cultivate, used as live food source in aquaculture. The growth characteristics of N. incerta were estimated under combinations of temperature, salinity, and light; and also its composition and antioxidant activities were determined. The maximum cell density of 87x10(5) cells/mL, was reached at 20 degrees C, 250 mu mol/m(2).sec, 33 parts per thousand salinity, pH 8.3, 12:12 light:dark, and F/2 medium on 2 weeks of the culture period. The antioxidant enzymatic hydrolysates efficiently quenched different free radicals: 1,1-diphenyl-2-pycryl-hydrazyl (DPPH) (pepsin IC50=196.0 mu g/mL), hydroxyl (alpha-chymotrypsin IC50=102.0 mu g/mL), and superoxide (neutrase IC50=169.0 mu g/mL). These results suggest that the enzymatic hydrolysate from N. incerta acts as a candidate against antioxidant and could be used as a potential functional food ingredient.