The dissolution of polysaccharides and amino acids enhanced lactic acid production from household food waste during pretreatment process

A large amount of household food waste (HFW) is produced yearly, resulting in environmental problems and financial burdens. Bio-production of lactic acid (LA), a high value-added platform chemical, from HFW by anaerobic fermentation is a promising way of resource recovery. However, the LA production yield from HFW is low. This paper compared several pretreatment methods (hydrothermal pretreatment, chemical pretreatment, and combined hydrothermal and chemical pretreatment) to improve LA production from HFW. The result showed that the combined pretreatment (alkali-thermal pretreatment at pH 10 and 120 degrees C) significantly increased the LA production than single hydrothermal and chemical pretreatment. The pretreatment process promoted the dissolution of organics, especially the polysaccharides and amino acids, and further influenced the LA production by Lactobacillus rhamnosus ATCC 7469. Among the amino acids, aspartic acid (Asp), threonine (Thr), glutamic acid (Glu), glycine (Gly), alanine (Ala), cystine (Cys), valine (Val), isoleucine (Ile), arginine (Arg), and proline (Pro) significantly correlated with LA concentration.