Effect of Lignocellulose Related Compounds on Microalgae Growth and Product Biosynthesis: A Review

Abstract

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...

Effect of Organic Solvents on Microalgae Growth, Metabolism and Industrial Bioproduct Extraction: A Review

“…Microalgae are photosynthetic microorganisms [ 1 ] that include cyanobacteria, green microalgae, eustigmatophytes, diatoms, dinoflagellates, coccolithophores, as well as euglenoid species, which are regarded as microalgae [ 2 ] and/or photosynthetic protists [ 3 ], and Polytomella species, regarded as protozoa or as unicellular colourless algae [ 4 ]. Besides photosynthetic mechanism, many microalgae strains are capable of heterotrophic and mixotrophic growth, when organic carbon sources (sugars, organic acids, alcohols, phenolics) are available [ 5 ]. Nowadays, microalgae are strongly considered as a source of lipids and carotenoids for industrial purposes [ 6 , 7 ].…”

Effect of Enzymatic Beech Fagus Sylvatica Wood Hydrolysate on Chlorella Biomass, Fatty Acid and Pigment Production

“…In our previous study [13], neutralized beech wood diluted acid hydrolysate at a 12% loading partially inhibited Chlorella growth, when compared to a synthetic organic carbon-based medium. In the literature, lignocellulosic hydrolysates contain a range of compounds that inhibit the metabolism of yeast [26,27], and can also negatively affect microalgae growth [10]. In the present study, neutralized enzymatic beech wood hydrolysate at 10% loading (TGP-Enz10) also inhibited Chlorella growth.…”

“…Lignocellulosic hydrolysates also have potential to be used as feedstocks for microalgae growth and biocompound production [10]. Hence, in this study, an enzymatic hydrolysate from alkali pretreated beech Fagus sylvatica wood was tested as a feedstock for Chlorella cultures.…”

Microalgal lipid production using the hydrolysates of rice straw pretreated with gamma irradiation and alkali solution

“…The sodium content was also increased after the pretreatment which might be due to the alkali pretreatment. Trace amounts of non-essential heavy metals, which can cause an inhibitory effect on the cell growth during fermentation, such as arsenic, cadmium and lead were also identified [ 16 ]. The results indicated that extracted elemental composition could be changed by pretreatment and the analysis may give the insight for eventual problems during the fermentation process.…”