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310 PROCEEDINGS OF INTERNATIONAL SCIENTIFIC CONFERENCE ON APPLIED BIOTECHNOLOGY2.5. Total flavonoids assayThe total flavonoid content of the culture was measured using the method of Yang et al. (2009). A 0.25 ml aliquot of the ethanolic extract was combined with 1.25 ml of distilled water and 75 %u03bcl of 5% NaNO2. After 6 minutes, 150 %u03bcl of 10% AlCl3was added, and the mixture was allowed to stand for 5 minutes before adding 0.5 ml of 1 M NaOH and 775 %u03bcl of distilled water. Absorbance was measured at 510 nm. Total flavonoid content was determined from a standard curve of quercetin (0 - 500 %u03bcg/ml) and expressed as micrograms of quercetin equivalent (%u03bcg QE) per gram of culture [13].2.6. Catalase activity assayThe method described by Teranishi was employed to evaluate catalase (CAT) activity. A 0.1 ml aliquot of the culture supernatant was combined with 1 ml of 2 mM H2O2 and 1.9 ml of phosphate buffer (0.1 M, pH 7.5). The mixture was incubated at 30%u00b0C for 5 minutes and subsequently halted with 4 ml of titanium reagent. The absorbance was measured at 415 nm after centrifugation at 3,000 rpm for 10 minutes. The enzyme activity was expressed as %u00b5moles of H2O2 per ml, and residual H2O2 was quantified against a standard curve. After cooling, the titanium reagent was diluted to a final volume of 1.5 L with water. This was achieved by dissolving 1 g of titanium oxide and 10 g of K2SO4 in 150 ml of concentrated H2SO2, heating the mixture for 2 hours, and then following the cooling process [14].2.7. Antioxidant activity measurementScavenging 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals was a way to measure the extract%u2019s antioxidant activity. A solution of dried extract was made in 96% ethanol and DPPH in 100%