We again screened a small library of ADHs and identified ADH 19 as an effective catalyst for the oxidation of triol 3a to monoaldehyde 4a. 3a was then treated with ADH 19 under the conditions of the cyclic reaction network: addition of 10 equivalents of ammonia borane at the outset of the reaction resulted in a reaction mixture comprising almost exclusively 3a after 48 hours (Figure ). When ammonia trideuteroborane (H3N•BD3) was used in place of ammonia borane, deuterium was gradually incorporated at the benzylic positions of 3a (Figure ), confirming that, under these conditions, chemically unchanged motor 3a is undergoing multiple cycles of oxidation and reduction. The continued viability of the cyclic redox reaction network over extended periods of time was confirmed by subjecting 3a to sub-stoichiometric pulses of ammonia borane at regular intervals, rather than a large excess at the outset of the reaction (Figure ). At the outset of the reaction, 3a was subjected to the standard oxidation conditions and after 24 hours, 51% conversion to monoaldehyde 4a was observed. A pulse of ammonia borane (approx. 0.2 equivalents) was added at 24 hours, followed by analysis at 1 hour (18% conversion to monoaldehyde 4a) and 24 hours (54% conversion to 4a), confirming that the oxidation system (ADH 19, NADP, and YcnD) was viable for at least 24 hours. A further 3 pulses of ammonia borane (3 x approx. 0.2 equivalents) were applied at 24 hour intervals. After each pulse, monoaldehyde 4a was regenerated in similar conversions (approx. 50%), confirming the viability of the oxidation system over at least 96 hours. By monitoring the background conversion of ammonia borane to boric acid (B(OH)3), we also confirm that 3a accelerates the fuel-to-waste conversion (see Supplementary Information Section 8 for details).