Sweet potato showed a high potential as a good resource for lactic acid production by Lactobacillus sp. An optimization of SP liquefaction hydrolysis by α-amylase was successfully achieved by using RSM. The optimal conditions obtained provided a liquefied product with high reducing sugars, which subsequently was a fermentation substrate for lactic acid production by an efficient process called SSF process. This process makes the production of lactic acid possible with at least 48-72 h faster since it is not necessary to completely hydrolyze the starch in to glucose prior to the beginning of fermentation.