초록
<P><B>Abstract</B></P> <P>Carbon dioxide (CO<SUB>2</SUB>) using biological process is one of the promising approaches for CO<SUB>2</SUB> capture and storage. Recently, biological sequestration using microalgae has gained many interest due to its capability to utilize CO<SUB>2</SUB> as carbon source and biomass produced can be used as a feedstock for other value added product for instance biofuel and chemicals. In this study, the CO<SUB>2</SUB> biofixation by two microalgae species, <I>Chlorella</I> sp. and <I>Tetraselmis suecica</I> was investigated using different elevated CO<SUB>2</SUB> concentration. The effect of CO<SUB>2</SUB> concentration on microalgae growth kinetic, biofixation and its chemical composition were determined using 0.04, 5, 15 and 30% CO<SUB>2</SUB>. The variation of initial pH value and its relationship on CO<SUB>2</SUB> concentration toward cultivation medium was also investigated. The present study indicated that both microalgae displayed different tolerance toward CO<SUB>2</SUB> concentration. The maximum biomass production and biofixation for <I>Chlorella</I> sp. of 0.64gL<SUP>−1</SUP> and 96.89mgL<SUP>−1</SUP> d<SUP>−1</SUP> was obtained when the cultivation was carried out using 5 and 15% CO<SUB>2,</SUB> respectively. In contrast, the maximum biomass production and CO<SUB>2</SUB> biofixation for <I>T. suecica</I> of 0.72gL<SUP>−1</SUP> and 111.26mgL<SUP>−1</SUP> d<SUP>−1</SUP> were obtained from cultivation using 15 and 5% CO<SUB>2</SUB>. The pH value for the cultivation medium using CO<SUB>2</SUB> was between 7.5 and 9, which is favorable for microalgal growth. The potential of biomass obtained from the cultivation as a biorefinery feedstock was also evaluated. An anaerobic fermentation of the microalgae biomass by bacteria <I>Clostridium saccharoperbutylacenaticum</I> N1-4 produced various type of value added product such as organic acid and solvent. Approximately 0.27 and 0.90gL<SUP>−1</SUP> of organic acid, which corresponding to acetic and butyric acid were produced from the fermentation of <I>Chlorella</I> sp. and <I>T. suecica</I> biomass. Overall, this study suggests that <I>Chlorella</I> sp. and <I>T. suecica</I> are efficient microorganism that can be used for CO<SUB>2</SUB> biofixation and as a feedstock for chemical production.</P> <P><B>Highlights</B></P> <P> <UL> <LI> CO<SUB>2</SUB> biofixation by <I>Chlorella</I> sp. and <I>T. suecica</I> </LI> <LI> CO<SUB>2</SUB> concentration effects on pH and microalgae growth </LI> <LI> Both microalgae capable to growth in elevated CO<SUB>2</SUB> concentration </LI> <LI> Organic acid and solvent can be produced from fermentation of microalgae biomass. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>