title: L: (+)-Lactic acid production from non-food carbohydrates by thermotolerant Bacillus coagulans.
abstract: Lactic acid is used as an additive in foods, pharmaceuticals, and cosmetics, and is also an industrial chemical. Optically pure lactic acid is increasingly used as a renewable bio-based product to replace petroleum-based plastics. However, current production of lactic acid depends on carbohydrate feedstocks that have alternate uses as foods. The use of non-food feedstocks by current commercial biocatalysts is limited by inefficient pathways for pentose utilization. B. coagulans strain 36D1 is a thermotolerant bacterium that can grow and efficiently ferment pentoses using the pentose-phosphate pathway and all other sugar constituents of lignocellulosic biomass at 50°C and pH 5.0, conditions that also favor simultaneous enzymatic saccharification and fermentation (SSF) of cellulose. Using this bacterial biocatalyst, high levels (150-180 g l(-1)) of lactic acid were produced from xylose and glucose with minimal by-products in mineral salts medium. In a fed-batch SSF of crystalline cellulose with fungal enzymes and B. coagulans, lactic acid titer was 80 g l(-1) and the yield was close to 80%. These results demonstrate that B. coagulans can effectively ferment non-food carbohydrates from lignocellulose to L: (+)-lactic acid at sufficient concentrations for commercial application. The high temperature fermentation of pentoses and hexoses to lactic acid by B. coagulans has these additional advantages: reduction in cellulase loading in SSF of cellulose with a decrease in enzyme cost in the process and a reduction in contamination of large-scale fermentations.
authors.affiliation: Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, USA.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Ou
authors.forename: Lonnie O
authors.initials: LO
authors.lastname: Ingram
authors.forename: K T
authors.initials: KT
authors.lastname: Shanmugam
mesh_terms: D001407:Bacillus / Q000201:enzymology / Q000378:metabolism*; D002480:Cellulase / Q000378:metabolism; D002482:Cellulose / Q000378:metabolism; D005285:Fermentation; D005947:Glucose / Q000378:metabolism*; D019344:Lactic Acid / Q000378:metabolism*; D010427:Pentose Phosphate Pathway; D014994:Xylose / Q000378:metabolism*
chemical_list: D019344:Lactic Acid; D002482:Cellulose; D014994:Xylose; D002480:Cellulase; D005947:Glucose