BioChem - DOS

L-Lactic acid production from liquefied cassava starch by thermotolerant Rhizopus microsporus: Characterization and optimization

Process biochemistry

Trakarnpaiboon, Srisakul; Srisuk, Nantana; Piyachomkwan, Kuakoon; Yang, Shang-Tian; Kitpreechavanich, Vichien

<P><B>Abstract</B></P> <P>The thermotolerant <I>Rhizopus microsporus</I> DMKU 33 capable of producing <SMALL>L</SMALL>-lactic acid from liquefied cassava starch was isolated and characterized for its phylogenetic relationship and growth temperature and pH ranges. The concentrations of (NH<SUB>4</SUB>)<SUB>2</SUB>SO<SUB>4,</SUB> KH<SUB>2</SUB>PO<SUB>4</SUB>, MgSO<SUB>4</SUB> and ZnSO<SUB>4</SUB>&middot;7H<SUB>2</SUB>O in the fermentation medium was optimized for lactic acid production from liquefied cassava starch by <I>Rhizopus microsporus</I> DMKU 33 in shake-flasks at 40&deg;C. The fermentation was then studied in a stirred-tank bioreactor with aeration at 0.75vvm and agitation at 200rpm, achieving the highest lactic acid production of 84g/L with a yield of 0.84g/g at pH 5.5 in 3days. Lactic acid production was further increased to 105&ndash;118g/L with a yield of 0.93g/g and productivity of 1.25g/L/h in fed-batch fermentation. <I>R. microsporus</I> DMKU 33 is thus advantageous to use in simultaneous saccharification and fermentation for <SMALL>L</SMALL>-lactic acid production from low-cost starchy substrates.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A novel thermotolerant <I>Rhizopus microsporus</I> was isolated and characterized. </LI> <LI> <SMALL>L</SMALL>-lactic acid production from liquefied cassava starch at 40&deg;C was studied. </LI> <LI> 84.3g/L lactic acid at 0.84g/g yield was obtained in batch fermentation at pH 5.5. </LI> <LI> Fed-batch gave 105&ndash;119g/L of lactic acid with a yield of 0.93g/g and productivity of 1.25g/L/h. </LI> <LI> The strain can be used in SSF for lactic acid production from starchy substrates. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

2017

Elsevier

1359-5113

63

pp.26-34

10.1016/j.procbio.2017.08.019

http://click.ndsl.kr/servlet/OpenAPIDetailView?keyValue=05787966&target=NART&cn=NART79610691

L-lactic acid; Cassava starch; Rhizopus microsporus; Simultaneous saccharification and fermentation; Thermotolerant