Abstract

The optimal conditions of lactic acid fermentation of undiluted oil palm trunks (OPTs) juice by L. rhamnosus TISTR 108 were investigated. The conditions with and without nutrient supplementation were studied. In the condition of no nutrient supplementation, fermentation at 10% inoculum, 40 °C and pH of 6.5 could enhance growth and lactic acid production. The highest lactic acid yield and productivity were obtained at 0.78 g g^-1 and 1.36 g l^-1h^-1, respectively. However sugars were found to remain in fermentation broth and the fermentation time was prolonged to 72 h. In the condition of nutrient supplementation, 10 g l^-1 of yeast extract, 5 g l^-1of peptone and salts were added into the fermentation process. It was found that the fermentation time was shortened to 21 - 54 h and the sugars were completely consumed. The highest lactic acid yields and productivities were achieved at 0.82 - 0.85 g g^-1 and 2.47 - 3.83 g l^-1h^-1, respectively.