The process for producing amino acids from volatile fatty acid (VFA) molecules, referred to as precursors, produced by anaerobic fermentation from fermentable biomass, comprises at least the following steps: a) extracting the volatile fatty acid (VFA) molecules, without stopping the fermentation, via an extraction means chosen from means that are, at least, insoluble in the fermentation medium, b) collecting, outside the fermentation reactor, the volatile fatty acid (VFA) molecules once they have been extracted, c) synthesizing, by halogenation, using a type of volatile fatty acid (VFA) chosen from the volatile fatty acids collected in step b) and defined according to the desired type of amino acid, a given α-halo acid, d) synthesizing from this α-halo acid a defined amino acid.