초록
<P><B>Abstract</B></P> <P>In this study, biological methanol production under repeated batch conditions by immobilized <I>Methylocystis bryophila</I>, using simulated biogas of methane (CH<SUB>4</SUB>) and carbon dioxide (CO<SUB>2</SUB>) as a feed is demonstrated for the first time. The composition of the simulated gas mixtures significantly influenced methanol production by <I>M. bryophila,</I> and in all cases, higher concentrations were achieved than with pure CH<SUB>4</SUB> alone. Under optimum conditions, maximum methanol concentrations of 4.88 mmol L<SUP>−1</SUP>, 7.47 mmol L<SUP>−1</SUP>, and 7.02 mmol L<SUP>−1</SUP> were achieved using the gas mixtures CH<SUB>4</SUB>:CO<SUB>2</SUB> (2:1 ratio), CH<SUB>4</SUB>:hydrogen [H<SUB>2</SUB>, (4:1 ratio)], and CH<SUB>4</SUB>:CO<SUB>2</SUB>:H<SUB>2</SUB> (6:3:2 ratio), respectively, as feed, with a fixed CH<SUB>4</SUB> concentration of 30%. Methanol yield was increased to 7.85 mmol L<SUP>−1</SUP> using covalently immobilized cells and the simulated gas mixture CH<SUB>4</SUB>:CO<SUB>2</SUB>:H<SUB>2</SUB> (6:3:2 ratio). Under repeated batch conditions, immobilized cells produced a significantly higher cumulative methanol concentration (25.75 mmol L<SUP>−1</SUP>) than free cells (15.50 mmol L<SUP>−1</SUP>), using a simulated biogas mixture of CH<SUB>4</SUB>:CO<SUB>2</SUB> (2:1) and eight reuse cycles, suggesting that this mixture can potentially be utilized as a feed for the production of methanol. Furthermore, the effective utilization of low-cost feedstock, derived from natural sources, containing gas mixtures of CH<SUB>4</SUB>:CO<SUB>2</SUB>, CH<SUB>4</SUB>:H<SUB>2</SUB>, or CH<SUB>4</SUB>:CO<SUB>2</SUB>:H<SUB>2</SUB>, constitute an economical and environmentally friendly approach to the reduction of greenhouse gases.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Methanol production was demonstrated by immobilized <I>Methylocystis bryophilla.</I> </LI> <LI> Simulated biogas as feed showed higher methanol production than pure CH<SUB>4</SUB>. </LI> <LI> A maximum methanol production of 7.85 mM was obtained from CH<SUB>4</SUB>:CO<SUB>2</SUB>:H<SUB>2</SUB>. </LI> <LI> Immobilized cells produced a higher cumulative methanol (25.75 mM) than free cells. </LI> </UL> </P>