Rice and wheat brans, without additional nutrients and hydrolyzed by alpha-amylase and amyloglucosidase, were fermented to DL-lactic acid using a newly isolated strain of Lactobacillus sp. RKY2. In batch fermentations at 36 degreesC and pH 6, the amount of lactic acid in fermentation broth reached 129 g 1(-1) by supplementation of rice bran with whole rice flour. The maximum productivity was 3.1 g lactic acid 1(-1) h(-1) in rice bran medium supplemented with whole rice flour or whole wheat flour.