Novel technological process for producing high optical purity L-lactic acid by semi-continuous high-density fermentation of Rhizopus oryzae

The invention discloses a novel technique for producing high optical purity L-lactic acid through rhizopus oryzae high cell density fermentation by a semi-continuous way, which relates to the following steps: (1) preparing rhizopus oryzae spore suspension; (2) preparing seed culture; (3) high-density thalli amplification; (4) 500L fermentation cylinder for the first batch fermentation; (5) 500L fermentation cylinder for high-density fermentation by the semi-continuous way-the first 5 times thalli proliferation and repeat fermentation; and (6) the last 20 times 500L fermentation cylinder for high-density and high-intensity repeat fermentation. The technique realizes semi-continuous fermentation by repeatedly using rhizopus oryzae thallis and increases the use ratio of raw material; the thallis are constructed in high density so that the fermentation period is shortened to be 18h and the fermentation intensity is increased to be 5.0g/(h*L), thus the technique has good industrial production prospect; the optical