BACILLUS-STEAROTHERMOPHILUS FOR THERMOPHILIC PRODUCTION OF L-LACTIC ACID

A process for the continuous production of high purity L-lactic acid i n a membrane bioreactor at 65 degrees C has been developed. Two differ ent Bacillus stearothermophilus strains have been tested in batch expe riments. Lactic acid yields are between 60 and more than 95% of theore tical yields. The amounts of ethanol, acetate, and formate formed vari ed between 0 and 0.4, 0 and 0.1, and 0 and 0.5, respectively (mol/mol glucose). All byproducts are valuable and may be separated easily by r ectification of the fermentation broth. Complete cell retention enable s high volumetric productivity (5 g/Lh), and a minimum of growth suppl ements. The high temperature of 65 degrees C allows the autoselective fermentation without problems with contamination.