Secondary acetate fermentation

A two-stage system for producing at least one target product from a gaseous stream comprising CO and optionally H2, or CO2 and H2, the system comprising:

• i. a primary bioreactor comprising a media inlet port, a gas inlet port, a first output conduit connected to an outlet port, and a bleed stream outlet connected to a bleed stream outlet conduit;
• ii. a primary separator comprising a first conduit inlet port connected to the output conduit of the primary bioreactor, a first primary permeate stream outlet connected to a primary permeate stream outlet conduit, and a second primary permeate stream outlet connected to a first return conduit, the first return conduit in fluid communication with the primary bioreactor;
• iii. a secondary bioreactor, in fluid communication with the bleed stream outlet conduit of the primary bioreactor and the primary permeate stream outlet conduit of the primary separator, the secondary bioreactor comprising, a tail gas stream outlet connected to a tail gas stream conduit, a first output port connected to a first output conduit, and a broth bleed output port connected to a broth bleed conduit;
• iv. a secondary separator, comprising a second inlet port in fluid communication with the first output conduit of the secondary bioreactor, a retentate outlet port connected to a retentate return conduit which is in fluid communication with the secondary bioreactor through a retentate inlet port, and a second permeate stream outlet port connected to a second permeate stream conduit comprising the at least one target product;
• and
• v. an oxygen removal unit having a tail gas stream inlet port connected to the tail gas stream outlet conduit of the secondary bioreactor, a CO2 enriched outlet port connected to a CO2 enriched conduit in fluid communication with a CO2 enriched inlet port on the primary bioreactor, and an O2 enriched stream outlet port connected to an O2 enriched stream conduit.