Abstract
The production of lactic acid from triticale starch was demonstrated for the first time. Direct fermentation by Rhizopus oryzae in batch mode led to a conversion yield of 0.74 g lactic acid/g starch. Kinetics analysis of the fermentation suggested a multiphase process which consisted of quick hydrolysis of starch, rapid glucose accumulation followed by fast production of lactic acid. In batch fermentation mode, correct timing and proper dosage of a neutralizing agent (calcium carbonate) were found to be critical factors that affect the organic acid yield. Addition of CaCO3 at the time point when glucose accumulation had reached its peak (24 h) resulted in the highest lactic acid yield. The best ratio (by weight) of triticale starch to CaCO3 for lactic acid production was 1:1. It was important to maintain a pH of about 5 during the whole fermentation process. Fermentation carried out in an optimized, commercially available small-scale parallel bioreactor (DASGIP) yielded up to 0.87 g lactic acid/g triticale starch when R. oryzae spores were directly added to the fermentation medium. Our fermentation results indicated that triticale starch from this nonfood crop is a promising renewable feedstock for production of lactic acid.
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