초록
<P>This paper reports the design and preparation of a biohybrid photoelectrochemical cell (PEC) that can drive the tandem enzymatic oxidation and aldol condensation of <I>n</I>-butanol (BuOH) to C<SUB>8</SUB> 2-ethylhexenal (2-EH). In this work, BuOH was first oxidized to <I>n</I>-butyraldehyde (BA) by the alcohol oxidase enzyme (AOx), concurrently generating hydrogen peroxide (H<SUB>2</SUB>O<SUB>2</SUB>). To preserve enzyme activity and increase kinetics nearly 2-fold, the H<SUB>2</SUB>O<SUB>2</SUB> was removed by oxidation at a bismuth vanadate (BiVO<SUB>4</SUB>) photoanode. Organocatalyzed aldol condensation of C<SUB>4</SUB> BA to C<SUB>8</SUB> 2-EH improved the overall BuOH conversion to 6.2 ± 0.1% in a biased PEC after 16 h. A purely light-driven, unbiased PEC showed 3.1 ± 0.1% BuOH conversion, or ∼50% of that obtained from the biased system. Replacing AOx with the enzyme alcohol dehydrogenase (ADH), which requires the diffusional nicotinamide adenine dinucleotide cofactor (NAD<SUP>+</SUP>/NADH), resulted in only 0.2% BuOH conversion due to NAD<SUP>+</SUP> dimerization at the photoanode. Lastly, the application of more positive biases with the biohybrid AOx PEC led to measurable production of H<SUB>2</SUB> at the cathode, but at the cost of lower BA and 2-EH yields due to both product overoxidation and decreased enzyme activity.</P><P>Design and preparation is presented of a biohybrid photoelectrochemical cell that drives tandem enzymatic oxidation and aldol condensation of <I>n</I>-butanol to C<SUB>8</SUB> 2-ethylhexenal.</P><P><B>Graphic Abstract</B><BR><IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ascecg/2017/ascecg.2017.5.issue-9/acssuschemeng.7b01849/production/images/medium/sc-2017-01849e_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/sc7b01849'>ACS Electronic Supporting Info</A></P>