Open fermentative production of l-lactic acid using white rice bran by simultaneous saccharification and fermentation

• A two-stage strategy was efficiently used for l-lactic acid production from WRB.
• A stepwise controlled pH was proposed for indigenous bacteria suppression.
• A balanced process was obtained under an open SSF process.

To reduce raw material cost for lactic acid production, white rice bran as an important byproduct in rice milling, was used in l-lactic acid production by open simultaneous saccharification and fermentation (SSF). Although one thermotolerant strain was used at a temperature as high as 50 °C, the open fermentation was still inefficient due to the indigenous thermophilic bacteria from corn steep liquor powder. A stepwise controlled pH was proposed in open SSF process, and no complicated pretreatment or sterilization was needed before fermentation. In batch fermentation, 117 g L−1 lactic acid was obtained, and the productivity and yield reached 2.79 g L−1 h−1 and 98.75%, respectively. These results showed an efficient way to develop high value-added products from white rice bran.

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