Heterotrophy compared to phototrophy for growth characteristics and pigment compositions in batch cultures of four green microalga

Growth curves of four species of green microalgae have been compared under photoautotrophy, heterotrophy and dim-light-assisted heterotrophy during batch cultivation in small-scale multicultivators equipped with automated optical density acquisition. The results showed that the most relevant biomass productivity parameter (based on Vmax) can be estimated after proper correction of growth curves. For photoautotrophic cultures, Vmax showed no clear relationship to µmax, the specific growth rate measured during exponential phase. Heterotrophic cultures, which are not limited by light penetration, can be characterized by their µmax values, which showed a broad range of values depending more on species than on carbon source (glucose or acetate). Weak light (defined as unable to sustain photoautotrohic growth) had only minor effects on heterotrophic growth in terms of biomass but, for some species, could be used to promote pigment accumulation up to levels comparable to those found under photoautotrophy, as revealed by HPLC analysis