While alcohol oxidases have been previously applied to the oxidation of diols, access to the di-aldehyde is often limited by overoxidation or the interception of intermediate hemiacetal tautomers to form lactones. Initial analytical scale biotransformations analysed by GC-MS showed no presence of carboxylic acids or δ-valerolactone (2) when 1,5-pentanediol (3) was subjected to oxidation by AcCO6, although glutaraldehyde (5) was also unobserved. We next sought to test the coupling of 3 with allylamine (v) under the standard AcCO6-RedAm cascade conditions outlined previously, with the better expressing "AdRedAm" used in lieu of "AspRedAm". Unfortunately, we observed no product from this biotransformation. Hypothesing that perhaps the intermediate hemiacetal intermediate tautomer (1) may be intercepted and oxidised by the glucose dehydrogenase (GDH) enzyme "CDX-901" required for cofactor recycling, we measured the specific activity of CDX-901 cell free extract (CFE) with 5-hydroxypentanal (4) through an NADPH formation assay. CDX-901 was found to be active towards the oxidation of 4 and was replaced with the GDH from Thermoplasma acidophilum (TaGDH).