초록
<P><B>Abstract</B></P> <P>Biosynthesis of methanol from methane as a direct method takes place at ambient temperature and pressure which causes a considerable reduction in process costs. In this study an efficient methane transfer chamber along with an external-loop airlift bioreactor were developed to dissolve methane and oxygen in the culture separately. Mass transfer coefficients for oxygen in the bioreactor and methane in the transfer chamber were obtained 97.2h<SUP>−1</SUP> and 70.8h<SUP>−1</SUP> respectively. Two strains of methanotroph bacteria (<I>AS1</I> and <I>AS2</I>) were also isolated from activated sludge. Factorial design of experiments for operational parameters showed a maximum productivity for <I>AS1</I> strain at 28°C when using nitrate as nitrogen source. Batch runs in airlift bioreactor using the <I>AS1</I> strain and optimized operating parameters represented a peak of 1600mg/L in methanol synthesis during the first 3:30h without using inhibitor for methanol dehydrogenase (MDH) enzyme. Sequencing batch process, at the next step, was used to create intermediate lag phase and to increase the stability of microorganisms by forming flocs. The results of this study cleared that the designed system is safe and efficient to scale-up, and it can be considered as a potential alternative method in the production of methanol.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Two methanotrophs (AS1, AS2) were isolated for methane bioconversion to methanol. </LI> <LI> AS1 had the optimum productivity at 28°C when nitrate was used as nitrogen source. </LI> <LI> Methane transfer chamber increased methane dissolution rate and system’s safety. </LI> <LI> Airlift bioreactor declined methanol accumulation time and increased its concentration. </LI> <LI> Sequencing batch run led to create microbial flocs for high cell density system. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>