One‐pot synthesis of 6‐aminohexanoic acid from cyclohexane using mixed‐species cultures

6‐Aminohexanoic acid (6AHA) is a vital polymer building block for Nylon 6 production and an FDA‐approved orphan drug. However, its production from cyclohexane is associated with several challenges, including low conversion and yield, and severe environmental issues. We aimed at overcoming these challenges by developing a bioprocess for 6AHA synthesis. A mixed‐species approach turned out to be most promising. Thereby, Pseudomonas taiwanensis VLB120 strains harbouring an upstream cascade converting cyclohexane to either є‐caprolactone (є‐CL) or 6‐hydroxyhexanoic acid (6HA) were combined with Escherichia coli JM101 strains containing the corresponding downstream cascade for the further conversion to 6AHA. ε‐CL was found to be a better ‘shuttle molecule’ than 6HA enabling higher 6AHA formation rates and yields. Mixed‐species reaction performance with 4 g l(‐1) biomass, 10 mM cyclohexane, and an air‐to‐aqueous phase ratio of 23 combined with a repetitive oxygen feeding strategy led to complete substrate conversion with 86% 6AHA yield and an initial specific 6AHA formation rate of 7.7 ± 0.1 U g(CDW) (‐1). The same cascade enabled 49% 7‐aminoheptanoic acid yield from cycloheptane. This combination of rationally engineered strains allowed direct 6AHA production from cyclohexane in one pot with high conversion and yield under environmentally benign conditions.