Optimized IBE fermentation method for upgrading acetone

A process for producing alcohols comprising the following steps:

• a. a fermentation step using a reaction section comprising at least one bioreactor wherein an Isopropanol-Butanol-Ethanol-type fermentation is carried out in the presence of a strain of Clostridium that naturally synthesizes, during fermentation, at least one secondary alcohol dehydrogenase (sadh) enzyme that enables the conversion of acetone to isopropanol in the presence of nicotinamide adenine dinucleotide phosphate (NADPH), said reaction section being fed at least with an aqueous solution of C5 or C6 sugars or a combination thereof and a recycled acetone stream, in order to produce fermentation gases and a fermentation broth containing fermentation products comprising butanol, ethanol, isopropanol and acetone;
• b. a step of recovering the fermentation products, in order to obtain a stream of fermentation products;
• c. a step of treating the stream of fermentation products from step b) using an acetone separation section in order to produce at least an acetone effluent having an acetone concentration of greater than or equal to 95% by weight, relative to the weight of said acetone effluent, and an aqueous alcohol effluent;
• d. a step of recycling the acetone which uses at least one transfer section in order to recycle at least one fraction of the acetone effluent from step c) to step a), said at least one fraction of the acetone effluent which is transferred constituting said recycled acetone stream which feeds the reaction section of step a).