Microalgae contain valuable compounds that can be harnessed for industrial applications. Lignocellulose biomass is a plant material containing in abundance organic substances such as carbohydrates, phenolics, organic acids and other secondary compounds. As growth of microalgae on organic substances was confirmed during heterotrophic and mixotrophic cultivation, lignocellulose derived compounds can become a feedstock to cultivate microalgae and produce target compounds. In this review, different treatment methods to hydrolyse lignocellulose into organic substrates are presented first. Secondly, the effect of lignocellulosic hydrolysates, organic substances typically present in lignocellulosic hydrolysates, as well as minor co-products, on growth and accumulation of target compounds in microalgae cultures is described. Finally, the possibilities of using lignocellulose hydrolysates as a common feedstock for microalgae cultures are evaluated.Keywords: lignocellulose; hydrolysis; microalgae; cultivation; extraction; bioproducts
OPEN ACCESSEnergies 2014, 7 4447
Microalgae: A Source of Valuable CompoundsMicroalgae include several groups of microorganisms that belong to the Prokaryota or Eukaryota, typically found in fresh water or marine systems in single cell forms or in groups. They are capable of performing photosynthesis, producing approximately half of the atmospheric oxygen while using the greenhouse gas carbon dioxide to grow photoautotrophically [1]. Microalgae contain valuable compounds such as lipids, proteins and pigments (Table 1) which have substantial potential for commercial applications. Microalgae cells accumulate lipids which include triacylglycerides (TAGs), polyunsaturated fatty acids (PUFAs) and sterols [2]. These lipids constitute storage materials or membrane structural components in microalgae and can be used for biofuel, food supplement and pharmaceutical production. Indeed, fossil fuels are nowadays still the main source of carbon based fuels, the exploitation of which causes emission of greenhouse CO 2 . Biodiesel production from oil crops is seen as currently the best alternative, but still presents the main drawback of competing with food production for arable land. Therefore, production of biodiesel from TAGs present in microalgae can become an environmentally friendly alternative as microalgae produce oil and fix CO 2 from atmosphere without the necessity of implementing vast arable areas for cultivation [3]. On the other hand, consumption of PUFAs in the human diet can help prevent the development of cardiovascular and mental diseases [4]. Fish are a rich source of PUFAs, but uncontrolled fishing has led to a substantial decrease in the worldwide fish population [5]. Production of PUFAs from microalgae may overcome this problem. On the other hand, sterols from microalgae are important part of the diet for juvenile scallops or prawns in aquaculture hatcheries [6]. Moreover, the high protein content in microalgae makes them a possible fodder for agricultural livestock [7]. In ad...