Carotenoids and pH of the culture medium play an important role in displaying metal stress in batch and semi-continuous cultures ofAnabaena doliolum

Abstract

-We analysed the responses of Anabaena doliolum to elevated levels of copper and zinc in batch and semi-continuous cultures. Approximately 10, 4 and 8 and 5-times greater inhibition in final yield of A. doliolum occurred at 1, 2 mM Cu and 2.5 and 5 mM of Zn, respectively, in semi-continuous culture in comparison to batch culture. Protein, chlorophyl a and carotenoid contents of A. doliolum showed significantly (P < 0.05) higher inhibition by test metals in semi-continuous culture than in batch culture. The greater sensitivity of different parameters of the test organism was related to the high metal content of the cells grown in semi-continuous system. Moreover, enhancement of pH of the culture suspension in batch culture showed a negative relationship with metal accumulation, and therefore with toxicity. This was due to decrease in free ionic concentrations of test metals. Carotenoids acted as a metal detoxifying agent by minimizing metal-induced inhibition in batch culture as was evident from its negative relationship with metal toxicity.

Diurnal variations of dissolved and colloidal organic carbon and trace metals in a boreal lake during summer bloom

“…The independence of Zn on pH and other macroscopic parameters of solution variations (Fig. 3D) is at first glance surprising because Zn uptake by phytoplankton is strongly pHdependent (Gé labert et al, 2006;Pokrovsky et al, 2008a,b;Tripathi et al, 2009) and Zn concentration during the bloom often follows that of the Chl a (Luengen et al, 2007). However, it is possible that the diel pH variations (from 7.4 to 8.4) is above that of Zn adsorption on cell surface when 100% of adsorption is achieved at pH >7.…”

Diurnal variations of trace metals and heterotrophic bacterioplankton concentration in a small boreal lake of the White Sea basin

“…The variation of Zn concentration in the surface water of lake Vilno is almost an order of magnitude higher than that of the Chl a. The independence of Zn on pH and other macroscopic parameters of solution variations is at first glance surprising because Zn uptake by phytoplankton is strongly pH-dependent (Ge´labert et al, 2006;Tripathi et al, 2009) and Zn concentration during the bloom often follows that of the Chl a (Luengen et al, 2007). Moreover, the pH is known to be the governing factor of metal adsorption on the surface of photosynthetic microorganisms such as diatoms or cyanobacteria (Ge´labert et al, 2007;Pokrovsky et al, 2008aPokrovsky et al, , 2008b.…”

Exploring the potential of freshwater algal species for biofuel production

“…In this study, the algal species were grown in batch culture. Batch culture depletes nutrients over time, leading to nutrient limitation and pH drift in the culture medium (Tripathi et al, 2003;Tripathi et al, 2009). Nutrient limitation occurring over time in batch culture may have induced lipid production in these algal species in a timedependent manner in this study.…”