Recovery of alkyl lactate from ammonium lactate by an advanced precipitation process

The recovery of lactic acid from ammonium lactate solution is impossible by the conventional acidification process because of the high solubility and lack of precipitation of ammonium sulfate. We found that only the addition of methanol to the solution during acidification of ammonium lactate was very effective in decreasing the solubility of the produced ammonium sulfate. This product could then be separated from the solution by simple filtration. With this advanced acidification process, the lactic acid filtrate was transformed into methyl lactate rapidly by an esterification reaction with methanol even at room temperature. The methyl lactate produced from the fermentation broth of ammonium lactate by this technique could be separated by simple distillation without change in the optical purity of lactic acid. This approach is simple and cost effective because all processes can be carried out at room temperature without complicated equipment. It is also regenerative because the ammonium sulfate byproduct can be utilized for production of sulfuric acid and ammonia.

► We developed an advanced acidification process for lactic acid recovery. ► Addition of methanol was effective in separation of ammonium sulfate precipitate. ► The recovery yield of lactic acid from fermented ammonium lactate was 100%. ► Methyl lactate yield was higher than 80% at room temperature. ► The new process scheme is very efficient and cost effective.