Effects of H2O2 acclimation on the growth, polysaccharide production and tolerance performance of Nostoc flagelliforme

Based on our previous findings that the increase of intracellular reactive oxygen species (ROS) level could significantly increase the extracellular polysaccharide (EPS) production in Nostoc flagelliforme, the strategy of continuously increasing the concentration of exogenous H2O2 was employed and the acclimated strain adapting to 2 mM H2O2 was obtained. The results showed that the polysaccharides yield of acclimated strain was increased by 27 % without reducing the biomass of N. flagelliforme. During H2O2 acclimation, the contents of malondialdehyde (MDA) and ROS were significantly increased, and various antioxidant indicators were also elevated. The acclimated N. flagelliforme had better adaptability to salt stress and higher H2O2 concentration, and still had higher polysaccharide yield when cultured under normal conditions. Two polysaccharides of the original strain (NC-CPS) and the acclimated strain (AH-CPS) were subsequently extracted and purified, and their physicochemical properties and antioxidant activity were compared. AH-CPS had similar Fourier transform infrared spectra with NC-CPS, but AH-CPS had higher molecular weight and intrinsic viscosity. The antioxidant experiment showed that AH-CPS had strong scavenging activity on hydroxyl radical and DPPH radical than NC-CPS. The results showed that a more tolerant strain with increased polysaccharide yield and activity could be obtained by H2O2 acclimation. It has better reference significance for obtaining high yield polysaccharides of other algae species.