Cultivation Medium Design Via Elemental Balancing for Tetraselmis suecica

M. K. Danquah, R. Harun, R. Halim and G. M. Forde

Abstract
The primary requirements for high-biomass-concentration microalgal cultivation include a photon source and distribution, efficient gas exchange and suitable growth medium composition. However, for mass outdoor production of microalgae, growth medium composition is a major controlling factor as most of the other factors such as light source and distribution are virtually uncontrollable. This work utilises an elemental balance approach between growth medium and biomass compositions to obtain high-density microalgal cultures in an open system. F medium, commonly used for the cultivation of marine microalgae such as Tetraselmis suecica was redesigned on the basis of increasing the biomass capacity of its major deficient components to support high biomass concentrations (φ ~ 5.0 % for N, S and φ ~ 10 % P), and the entire formulation was dissolved in 0.2 μm sterile filtered natural seawater. Results show that the new medium (F') displayed a maximum biomass concentration and total lipid concentration of 1.29 g L–1 and 108.7 mg L–1 respectively, which represents over 2-fold increase compared to that of the F medium. Keeping all variables constant except growth medium, and using F medium as the base case of 1 medium cost (MC) unit mg–1 lipid, the F' medium yielded lipid at a cost of only 0.35 MC unit mg–1 lipids. These results show that greater amounts of biomass and lipids can be obtained more economically with minimal extra effort simply by using an optimised growth medium.

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Keywords
microalgae, growth medium, elemental balancing, flue gas, biomass, economics