Antioxidant property and production of exopolysaccharide from Armillaria mellea in submerged cultures: Effect of culture aeration rate

Abstract

Effects of culture aeration rate on production and antioxidant property of exopolysaccharide (EPS) by Armillaria mellea were investigated in a 5‐L stirred‐tank bioreactor where an optimal biomass aeration rate of 1.2 vvm with 0.22 g/g cell yield and 0.6 vvm EPS formation rate with 7.66 mg/g product yield were achieved. A two‐stage aeration process to maximize the biomass and EPS productions proceeded with a 1.55‐fold enhancement (from 4.28 to 6.65 g/L) in biomass formation and a 2.68‐fold enhancement (from 86.9 to 233.2 mg/L) in the EPS production, as compared with those from the aeration rate of 0.3 vvm. The molecular weights of EPS in cultures of different aeration rates are closely correlated with their protein/polysaccharide ratios (R2=0.830) and EC50 (EC50, the effective concentration where the antioxidant property is 50%) values in antioxidant activity (R2=0.960), reducing power (R2=0.894) and chelating ability (R2=0.954). EPS from the two‐stage aeration rate culture shows a strong antioxidant property by the conjugated diene method, reducing power and chelating ability on ions. Therefore, we present results to regulate and to optimize A. mellea cultures to efficiently produce biomass and EPS. The fermented EPS has the potential to be used as for antioxidant‐related functional foods and pharmaceutical industries.

BiotecVisions 2011, November

“…EPS produced in the proposed optimal two‐stage aeration rate culture is not only produced at a high yield, but also displays a high molecular weight with effective antioxidant properties. /ug [10]

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