Sweet Sorghum Juice and Bagasse as Feedstocks for the Production of Optically Pure Lactic Acid by Native and Engineered
- PDF / 625,251 Bytes
- 9 Pages / 595.276 x 790.866 pts Page_size
- 43 Downloads / 187 Views
Sweet Sorghum Juice and Bagasse as Feedstocks for the Production of Optically Pure Lactic Acid by Native and Engineered Bacillus coagulans Strains Mark S. Ou 1 & Deepika Awasthi 1 & Ismael Nieves 1 & Liang Wang 1 & John Erickson 2 & Wilfred Vermerris 1,3 & L. O. Ingram 1 & K. T. Shanmugam 1
# Springer Science+Business Media New York 2015
Abstract Sweet sorghum is a bioenergy crop that produces large amounts of soluble sugars in its stems (3–7 Mg ha−1) and generates significant amounts of bagasse (15–20 Mg ha−1) as a lignocellulosic feedstock. These sugars can be fermented not only to biofuels but also to bio-based chemicals. The market potential of the latter may be higher given the current prices of petroleum and natural gas. The yield and rate of production of optically pure D-(−)- and L-(+)-lactic acid as precursors for the biodegradable plastic polylactide was optimized for two thermotolerant Bacillus coagulans strains. Strain 36D1 fermented the sugars in unsterilized sweet sorghum juice at 50 °C to L -(+)-lactic acid (∼150 g L −1 ; productivity, 7.2 g L−1 h−1). B. coagulans strain QZ19-2 was used to ferment sorghum juice to D-(−)-lactic acid (∼125 g L−1; productivity, 5 g L−1 h−1). Carbohydrates in the sorghum bagasse were also fermented after pretreatment with 0.5 % phosphoric acid at 190 °C for 5 min. Simultaneous saccharification and co-fermentation of all the sugars (SScF) by B. coagulans resulted in a conversion of 80 % of available carbohydrates to optically pure lactic acid depending on the B. coagulans strain used as the microbial biocatalyst. Electronic supplementary material The online version of this article (doi:10.1007/s12155-015-9670-6) contains supplementary material, which is available to authorized users. * K. T. Shanmugam [email protected] 1
Department of Microbiology and Cell Science - IFAS, University of Florida, P. O. Box 110700, Gainesville, FL 32611, USA
2
Department of Agronomy - IFAS, University of Florida, Gainesville, FL 32611, USA
3
UF Genetics Institute, University of Florida, Gainesville, FL 32611, USA
Liquefaction of pretreated bagasse with cellulases before SScF (L + SScF) increased the productivity of lactic acid. These results show that B. coagulans is an effective biocatalyst for fermentation of all the sugars present in sweet sorghum juice and bagasse to optically pure lactic acid at high titer and productivity as feedstock for bio-based plastics. Keywords Bacillus coagulans . Fermentation . Lactic acid . Sorghum bicolor
Introduction While much effort has been invested in microbial production of biofuels from feedstocks that do not compete with food production [1, 2], the current low price of petroleum and natural gas has raised concerns over the competitiveness of biofuels [3]. Fermentable sugars from bioenergy feedstocks can also be used for production of bio-based chemicals and polymers that are normally made from petroleum, thereby offering the same environmental benefits as the displacement of petroleum as transportation fuel [4]. Lactic acid is a commodity chemical
Data Loading...
