Photobiology of microalgae mass cultures: understanding the tools for the next green revolution

Several obstacles and limitations currently prevent the industrial exploitation of microalgae for feed, food and biofuel production. Photobioreactors (closed systems for algae cultivation) suffer from high-energy expenditures for mixing and cooling, while cultures in large-scale open ponds, which have a more favorable net energy ratio, are unstable ecosystems in which maintaining selected strains for long periods is difficult. Techniques for supplying nutrients and CO2, for mixing and for harvesting and processing the biomass in an energy-efficient manner are still under study and development. Despite these impediments and although microalgae are not superior to higher plants in terms of photosynthetic efficiency and productivity, microalgal cultures remain one of the most attractive sources of feed, food and next-generation biofuels since microalgae can be grown in saline or seawater on nonarable lands, can use fertilizers with an almost 100% efficiency, are able to attain much higher oil and protein yields than traditional crops and, being endowed with high growth rates, are easier to be improved via genetic and metabolic engineering