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Title: Fermentation of Corn Fiber Hydrolysate to Lactic Acid by the Moderate Thermophile Bacillus coagulans

Author
item Bischoff, Kenneth
item Liu, Siqing
item Hughes, Stephen
item Rich, Joseph

Submitted to: Biotechnology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2010
Publication Date: 2/14/2010
Citation: Bischoff, K.M., Liu, S., Hughes, S.R., Rich, J.O. 2010. Fermentation of corn fiber hydrolysate to lactic acid by the moderate thermophile Bacillus coagulans. Biotechnology Letters. 32:823-828.

Interpretive Summary: In this research, we discovered a strain of bacteria that grows at high temperature and produces lactic acid from mixed sugars. Improved microbial strains are needed to convert the mixed sugars derived from agricultural residues into fuels and chemicals. The new strain used all the sugars available in hydrolysates of corn fiber to produce L-lactate, a valuable chemical used in foods, cosmetics, and bio-based plastics. The strain has potential industrial application in bio-based refineries that produce value-added bioproducts from agricultural commodities.

Technical Abstract: Composted manure from a dairy farm in Texas was examined for thermophilic microorganisms by enrichment in xylose broth medium. Forty randomly picked isolates were identified as strains of Bacillus coagulans by sequence analysis of rRNA genes. One strain, designated as MXL-9, could convert mixed sugars of glucose, xylose, and arabinose to L-lactic acid with 85% yield at pH 6.0 and 50°C. The strain was tolerant to aldehyde growth inhibitors, with no difference in optical density observed in the presence of 2.5 g/l of either furfural or 5-hydroxymethylfurfural, and 4-hydroxybenzaldehyde (1.2 g/l), and vanillin (2.5 g/l) reducing the optical density to only 78% and 87%, respectively, of untreated controls. In a simultaneous saccharification and fermentation process, strain MXL-9 converted a dilute-acid hydrolysate of 100 g corn fiber/l to 39 g lactic acid/l in 72 h at 50°C. Because of its inhibitor tolerance and ability to fully utilize xylose and arabinose, B. coagulans strain MXL-9 has potential to be developed as a biocatalyst for the conversion of agricultural residues into valuable chemicals.