BioChem - DOS

Enhanced effectiveness of Rhizopus oryzae by immobilization in a static bed fermentor for L-lactic acid production

Process biochemistry

Pimtong, Varunee; Ounaeb, Siriporn; Thitiprasert, Sitanan; Tolieng, Vasana; Sooksai, Sarintip; Boonsombat, Ruethairat; Tanasupawat, Somboon; Assabumrungrat, Suttichai; Thongchul, Nuttha

<P><B>Abstract</B></P> <P>The static bed fermentor was successfully employed for cell immobilization in this study. By complete immobilization of <I>Rhizopus oryzae</I> on a fibrous matrix, cell-free fermentation broth resulted in improved mass transfer and easy operation compared with free cell fermentation in a typical stirred fermentor. Environmental conditions generated in this fermentor configuration favoring the immobilized <I>R. oryzae</I> to grow and produce lactic acid without substrate repression at high initial glucose concentration during batch cultivation. Approximately 67% of the theoretical lactate yield (0.50g/g) with the productivity of 1.05g/Lh and the final titer of 75.28g/L was obtained from fermentation with high glucose concentration (150g/L). Complete cell immobilization supported the continuous operation of lactic acid production by <I>R. oryzae</I> since cell wash out was diminished. When operating the continuous culture at an appropriate dilution rate, a sufficiently high concentration of lactic acid (72.32g/L) with a small amount of remaining glucose (<5g/L) was obtained. Impurities remaining in the hydrolysates were generally considered toxic to microbial conversion; nevertheless, immobilized cells in the static bed fermentor exerted high tolerance to the salt impurities (Na<SUP>+</SUP>, Cl<SUP>&minus;</SUP>) remaining in the cassava pulp hydrolysates to be used in lactate fermentation medium.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Less susceptible to the high glucose concentration found in immobilized <I>R. oryzae</I>. </LI> <LI> Steady-state, long term continuous culture obtained in the static bed fermentor. </LI> <LI> Increasing tolerance on toxicity in hydrolysate observed in immobilized <I>R. oryzae</I>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

2017

Elsevier

1359-5113

52

pp.44-52

10.1016/j.procbio.2016.09.020

http://click.ndsl.kr/servlet/OpenAPIDetailView?keyValue=05787966&target=NART&cn=NART77130466

Static bed fermentor; Lactic acid; Continuous culture; Glucose tolerance; Hydrolysates; Toxic impurities