Effect of carbon to nitrogen ratio on biomass composition of microalga Picochlorum sp.

Fototrofnim uzgojem mikroalge Picochlorum sp. pri različitim C:N omjerima, istražen je utjecaj na njezin rast i sastav biomase. Najveća postignuta koncentracija stanica od 3,61∙107 st mLˉ¹ zabilježena je u f/2 podlozi i podlozi C:N=13,52 mol molˉ¹. Najveći udjeli proteina (75,26 %) i lipida (9,27 %) zabilježeni su u podlozi s omjerom C:N=67,64 mol molˉ¹. Najveći udio u lipidima čine zasićene masne kiseline (oko 50 %), a najmanji jednostruko nezasićene masne kiseline (oko 6-12 %). S ciljem povećane akumulacije lipida proveden je šaržni uzgoj navedene mikroalge u dvije faze- s i bez izvora dušika. Prilikom limitacije dušikom u drugoj fazi u podlogama s 1 g Lˉ¹ i 2 g Lˉ¹ NaHCO₃, ustanovljeno je smanjenje udjela proteina s 49 % na 47 % te 42 % na 31 % i ukupnog klorofila s 2,48 % na 0,67 % te 2,09 % na 0,58 %, ali je rezultirala povećanom akumulacijom lipida u sastavu biomase u podlozi sa 2 g Lˉ¹ NaHCO₃ sa 3,07 % na 10,22 %. Osim toga, ustanovljena je promjena profila masnih kiselina pri čemu je povećan udio višestruko nezasićenih masnih kiselina u f/2 podlozi i podlozi sa 1 g Lˉ¹ NaHCO₃ u odnosu na podloge koje su sadržavale izvor dušika.Phototrophic cultivation of the microalga Picochlorum sp. at different C:N ratios, the influence on its growth and biomass composition was investigated. The highest achieved cell concentration of 3,61∙107 cells mLˉ¹ was recorded in f/2 medium and medium C:N=13,52 mol molˉ¹. The highest share of proteins (75,26 %) and lipids (9,27 %) were recorded in the medium with the ratio C:N=67,64 mol molˉ¹. The largest share in lipids are saturated fatty acids (about 50 %), and the smallest monounsaturated fatty acids (about 6-12 %). With the aim of increased lipid accumulation, batch cultivation of this microalga was carried out in two phases- with and without nitrogen sources. Nitrogen limitation in the second phase in media with 1 g Lˉ¹ and 2 g Lˉ¹ NaHCO₃, led to a decrease in protein content from 49 % to 47 % and 42 % to 31 % and total chlorophyll from 2,48 % to 0,67 % and 2,09 % to 0,58 % but resulted in increased lipid accumulation in the biomass composition in the medium with 2 g Lˉ¹ NaHCO₃ from 3,07 % to 10,22 %. In addition, a change in the obtained fatty acid profile is visible, with an increased share of polyunsaturated fatty acids in the f/2 medium and the medium with 1 g Lˉ¹ NaHCO₃ compared to the media containing the nitrogen source