BioChem - DOS

Simultaneous synthesis of lactic acid and hydrogen from sugars via capnophilic lactic fermentation by Thermotoga neapolitana cf capnolactica

Biomass & bioenergy

Pradhan, Nirakar; d’Ippolito, Giuliana; Dipasquale, Laura; Esposito, Giovanni; Panico, Antonio; Lens, Piet N.L.; Fontana, Angelo

<P><B>Abstract</B></P> <P>This study investigated the effect of the salinity level, buffering agent and carbon source on the hydrogen (H<SUB>2</SUB>) and lactic acid synthesis under capnophilic (CO<SUB>2</SUB>-assisted) lactic fermentation (CLF) by <I>Thermotoga neapolitana cf capnolactica</I> (DSM 33003). Several series of batch fermentation experiments were performed either in 0.12 L serum bottles for selection of the best performing conditions or in a 3 L fermenter for the best possible combination of conditions. The serum bottle study revealed that change in the salinity level of the culture medium from 0 to 35 g L<SUP>&minus;1</SUP> NaCl increased lactic acid synthesis by 7.5 times without affecting the H<SUB>2</SUB> yield. Use of different buffers (MOPS, TRIS or HEPES) did not affect the average H<SUB>2</SUB> yield of 3.0 &plusmn; 0.24 mol H<SUB>2</SUB> mol<SUP>&minus;1</SUP> of glucose and lactic acid synthesis of 13.7 &plusmn; 1.03 mM when the cultures were sparged by CO<SUB>2</SUB>. Among the carbon sources investigated, glucose was found to be the best performing carbon source for the CLF fermentation with 35 g L<SUP>&minus;1</SUP> of NaCl and 0.01 M of phosphate buffer. Hence, an up-scale experiment using a 3 L fermenter and the combination of the best performing conditions showed a 2.2 times more lactic acid synthesis compared to the 0.12 L serum bottle experiments. The study reveals the robustness and flexibility of the CLF-based technology using <I>T. neapolitana cf capnolactica</I> fermentation under various operating environmental conditions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Capnophilic lactic fermentation (CLF) mechanism was tested on a wide array of culture parameters. </LI> <LI> Higher salinity level improved lactic acid synthesis under CLF conditions. </LI> <LI> Bioconversion of different types of sugars to H<SUB>2</SUB> and lactic acid was investigated. </LI> <LI> Process scale-up from 0.12 to 3 L fermenter resulted in 2.2 times higher lactic acid production. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

2019

Elsevier

0961-9534

125

pp.17-22

10.1016/j.biombioe.2019.04.007

http://click.ndsl.kr/servlet/OpenAPIDetailView?keyValue=05787966&target=NART&cn=NART97242619

Thermophilic bacteria; Hydrogen; Lactic acid; Fermentation; Salinity level; Buffering agent