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The biorefinery of the heterotrophic marine microalga Crypthecodinium cohnii grown on low-cost substrates: Production of DHA and biodiesel
Publication . Martins, Daniela Fonseca; Moniz, Patrícia Maria Azevedo; Vicente, Maria Suzana Leitão Ferreira Dias
The present work explored the use of low-cost substrates for the cultivation of the marine heterotrophic microalga Crypthecodinium cohnii, to produce high concentrations of docosahexaenoic acid (DHA) and fatty acids for biodiesel production.
Three cultivations were conducted, in a benchtop bioreactor operated under fed-batch regime, using different nutrient sources: crude glycerol, sugarcane molasses and corn steep liquor (CSL), all industrial by-products. The use of crude glycerol and CSL as carbon and nitrogen sources (Assay I), presented the best results, with a biomass concentration of 10.69 g L-1, total fatty acids (TFA) content of 28.29% (w/w), TFA productivity of 19.31 mg L-1 h-1 and DHA productivity of 6.64 mg L-1 h-1.
After the cultivation, the lyophilized biomass obtained underwent a saponification reaction, to produce fatty acid soaps, which were further converted into fatty acid ethyl esters (FAEE). These compounds were fractionated, using the urea complexation method at different temperatures, to obtain a polyunsaturated FAEE rich fraction (with potential for food, pharmaceutical and cosmetic purposes) and a saturated and monounsaturated FAEE rich fraction (potentially for biodiesel purposes). At the crystallization temperature of -18ºC, in Assay I fractions with 91.6% purity of DHA ethyl ester and 88.0% purity of saturated and monounsaturated FAEE were obtained. In Assay III, fractions with 69.91% purity of DHA ethyl ester and 97.4% purity of saturated and monounsaturated FAEE were attained. Finally, physical parameters of the fractions rich in saturated and monounsaturated FAEE were estimated and confirmed to be appropriate for biodiesel production, after a hydrogenation step, according to limits defined by the European Standard EN 14214.
The attained results represent an innovative and sustainable method for producing DHA and biodiesel from C. cohnii, increasing the potential revenue generated by the entire process, since all compounds produced are valorised and no waste is generated, respecting the circular economy.
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Fundação para a Ciência e a Tecnologia
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3599-PPCDT
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PTDC/EAM-AMB/30169/2017