Title: Production of lactic acid from hemicellulose extracts by Bacillus coagulans MXL-9 Authors
|Walton, Sara -|
|Van Heiningen, Adriaan -|
|Van Walsum, G Peter -|
Submitted to: Journal of Industrial Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 16, 2010
Publication Date: May 8, 2010
Repository URL: http://hdl.handle.net/10113/48888
Citation: Walton, S.L., Bischoff, K.M., Van Heiningen, A.R., Van Walsum, G. 2010. Production of lactic acid from hemicellulose extracts by Bacillus coagulans MXL-9. Journal of Industrial Microbiology and Biotechnology. 37:823-830. Interpretive Summary: In this research, we used a strain of bacteria that grows at high temperature to produce lactic acid from mixed sugars derived from woody biomass. Improved microbial strains are needed to convert the mixed sugars derived from agricultural residues into fuels and chemicals. Lactic acid is a valuable chemical used in foods, cosmetics, and bio-based plastics. The strain was found to be well suited to industrial production of lactic acid due to its ability to withstand chemical inhibitors produced during pretreatment of woody biomass while rapidly consuming all pentose and hexose sugars at high product yields. The strain has potential industrial application in bio-based refineries that produce value-added bioproducts from agricultural commodities.
Technical Abstract: Bacillus coagulans MXL-9 was found capable of growing on pre-pulping hemicellulose extracts, utilizing all of the principle monosugars found in woody biomass. This organism is a moderate thermophile isolated from compost for its pentose utilizing capabilities. It was found to have high tolerance for inhibitors such as acetic acid and sodium which are present in pre-pulping hemicellulose extracts. Fermentation of 20 g/L xylose in the presence of 30 g/L acetic acid required a longer lag phase but overall lactic acid yield was not diminished. Similarly fermentation of xylose in the presence of 20 g/L sodium increased the lag time but did not affect overall product yield, though 30 g/L sodium proved completely inhibitory. Fermentation of hot water extracted Siberian larch containing 45 g/L total monosaccharides, mainly galactose and arabinose, produced 33 g/L lactic acid in 60 hrs and completely consumed all sugars. Small amounts of co-products were formed, including acetic acid, formic acid and ethanol. Hemicellulose extract formed during autohydrolysis of mixed hardwoods contained mainly xylose and was converted into lactic acid with a 94% yield. Green liquor extracted hardwood hemicellulose containing 10 g/L acetic acid and 6 g/L sodium was also completely converted into lactic acid at a 72% yield. The Bacillus coagulans MXL-9 strain was found to be well suited to production of lactic acid from lignocellulosic biomass due to its compatibility with conditions favorable to industrial enzymes and its ability to withstand inhibitors while rapidly consuming all pentose and hexose sugars of interest at high product yields.