Lactic acid recovery from fermentation broth of kitchen garbage by esterification and hydrolysis method

Kitchen garbage was utilized to produce lactic acid (LA) to reduce the corresponding cost. The whole process for pure LA production involved fermentation, esterification and hydrolysis. Kitchen garbage could produce 47.9 g L−1 LA with pH adjusted with ammonia to 6–7. Then the fermentation broth was concentrated by water evaporation, the ammonium lactate inside was esterified with the butanol to produce butyl lactate. Proper catalyst was studied to improve esterification rate, a cation-exchange resin modified by FeCl3 as a catalyst was proved to be effective. The esterification yield of ammonium lactate (NH4LA) could reach 96%. Pure LA was hydrolyzed from the obtained butyl lactate in presence of a cation-exchange resin in the H+ form as a catalyst. The catalyst for hydrolysis could be regenerated and reused to save the cost. LA production from the kitchen garbage could not only save cost, but also solve the pollution problems of kitchen garbage.