ABSTRACT
Microalgae are a potential important source for the production of value compounds. Bioprocessing of microalgae in terms of optimization of the cultivation conditions could increase the production of some target compounds that are accumulated under stress conditions. From a bioprocess engineering point of view, stress conditions could be any environmental stimulus that forces the cells to synthesize target metabolites. Bioprocess strategies for the accumulation of target compounds include nutrient starvation/limitation, or subjecting cells to any other cultivation condition (salinity, light, temperature, etc.) that could act as stimulus. In general, under stress conditions carbonaceous metabolites, such as carbohydrates or lipids, are accumulated, while nitrogenous ones, such as proteins and protein-based compounds, are down-synthesized. Under stress conditions some pigments, such as astaxanthin or β-carotene, or polyunsaturated fatty acids and phenolics, are accumulated as well, which are high-value compounds. However, in most cases there is a trade-off between accumulation of target compounds and growth rates, which might result in the reduction of the net productivity of the compound of interest. Microalgal products are of value and display good perspectives, and therefore there are research and engineering opportunities in developing optimized cultivation systems for enhanced production of microalgal high-value products.
