Growth and biomass production of Tetraselmis suecica and Dunaliella tertiolecta in a standard medium added with three products of zeolitic nature

At the end of the exponential growth phase, the cell concentrations of batch cultures of Tetraselmis suecica and Dunaliella tertiolecta grown in f medium added with 5, 10 and 20 mg l−1 of the zeolitic products Zestec 56, Zesep 56 and Zeben 06 (ZT56, ZS56 and ZB06) were similar to those obtained with the same medium without zeolites. At the end of the following period of slow growth, all the experimental media gave significantly higher concentrations of T. suecica than the control cultures, but only the addition of 20 mg l−1 of ZT56 and ZB06 gave significantly better results with D. tertiolecta. However, in all cases the final harvests of total and ash-free biomass were similar to those of the controls, indicating the presence of smaller or lighter cell in the experimental cultures. The effect of these products is to enhance cell division rates in the phase of slow growth, with no advantage in terms of biomass production.