6+ January - February 2015
Simultaneous saccharification and fermentation for lactic acid production
from sweet potato
Amnuai Adthalungrong, Chaowaree Adthalungrong* and Piyanut Kumnil
Horticulture Research Institute, Department of Agriculture, Chatuchak, Bangkok 10900, Thailand
Department of Microbiology, Faculty of Science, Silpakorn University, Nakhon Pathom 73000, Thailand
*Correspondent author: firstname.lastname@example.org
Simultaneous saccharification and fermentation (SSF) process has been employed in numerous of recent
researches since it is an efficient process for the production of a wide range of valuable products. In our present
research, sweet potato (SP) was converted into lactic acid by SSF process, which involved a liquefaction step with
?-amylase followed by the SSF step in which glucoamylase and lactic acid bacterial starter were incorporated.
Optimal conditions for a hydrolysis of SP by ?-amylase were investigated using response surface methodology (RSM)
with central composite design (CCD). SP was applied at 50% (w/v) in distilled water and incubation time was allowed
for 90 min. The results suggested that 0.155% ?-amylase (% v/SP weight), 70oC incubation temperature, pH 6.5, and
0.75 g/L CaCl
were optimal for liquefaction of SP and the high concentration of reducing sugars at 60.32 g/L was
predicted. Subsequently, the liquefied product was applied for lactic acid production using SSF process by a lactic acid
bacterium, FAG 302, which was eventually identified as Lactobacillus sp. and optimum temperature was determined.
From the results, optimal temperature for SSF step was selected at 34oC and 105.52 g/L lactic acid was yielded at 72 h.
Keywords : lactic acid, sweet potato, simultaneous saccharification and fermentation