BIOENERGY AND BIOFUELS
Effects of gas condition on acetic acid fermentation by Clostridium
thermocellum and Moorella thermoacetica (C. thermoaceticum)
Dung Van Nguyen
Received: 31 January 2017 /Revised: 22 May 2017 /Accepted: 1 June 2017 /Published online: 19 June 2017
Springer-Verlag GmbH Germany 2017
Abstract Fermentation with acetogens can be affected by
cultivation gas phase, but to date, there is not enough evidence
on that matter for Clostridium thermocellum and Moorella
thermoacetica. In this work, the effects of sparged CO
as sparged and non-sparged N
on these microorganisms were
studied using glucose and cellobiose as substrates. It was re-
vealed that sparged CO
and non-sparged N
growth and acetic acid production by C. thermocellum and
M. thermoacetica, while sparged N
inhibited both of the mi-
croorganisms. Notably, part of the sparged CO
fermented by the co-culture system and contributed to an
overestimation of the products from the actual substrate as
well as an erring material balance. The best condition for the
co-culture was concluded to be N
without sparging. These
results demonstrate the importance of cultivation conditions
for efficient fermentation by anaerobic clostridia species.
Keywords Carbon dioxide (CO
Acetic acid fermentation
Moorella thermoacetica (Clostridium
Acetic acid is an extensively used chemical and an important
building block for plastics, textiles, films, and food preserva-
tives (Agreda and Zoeller 1993; Ljungdahl et al. 1985). It is
largely manufactured from fossil resources, but with increas-
ing environmental concerns and uncertain petroleum avail-
ability, producing organic acids from renewable bioresources
became a major topic of research in the biorefinery field.
Under such a context, the co-culturing system using
Clostridium thermocellum and Moorella thermoacetica
(C. thermoaceticum) has been proposed by our research group
to transform lignocellulosic biomass into acetic acid after hot-
compressed water treatment (Saka et al. 2010).
C. thermocellum can convert high molecular weight com-
pounds such as cello-oligosaccharides and xylo-
oligosaccharides into lower molecular weight products
(Johnson et al. 1982b; Morag et al. 1990; Nakamura et al.
2011;Sakaetal.2013; Vieira et al. 2007).
M. thermoacetica, in its turn, can ferment these obtained com-
pounds, together with other low molecular weight products
such as monosaccharides (Ljungdahl 1986;Nakamuraetal.
2011), decomposed products, and organic acids into acetic
acid (Nakamura et al. 2011;Sakaetal.2013). Lignin-
derived products in low concentration were, on the other hand,
fermented by both microorganisms (Nakamura et al. 2011;
Saka et al. 2013). The co-culturing system was, therefore,
demonstrated to have a remarkable capacity to convert most
biomass-derived compounds into acetic acid (Nakamura et al.
2011; Rabemanolontsoa et al. 2016), and then into ethanol
after hydrogenolysis (Ito et al. 2016).
One important consideration in co-culture is to find param-
eters which are mutually advantageous to the microorganisms.
C. thermocellum and M. thermoacetica are both gram-posi-
tive, acetogenic, strictly anaerobic, and thermophilic bacteria
with optimum temperature of 60 °C (Fontaine et al. 1942;
Schwarz 2001). C. thermocellum is often cultivated under
nitrogen atmosphere without sparging (Islam et al. 2006;
Weimer and Weston 1985), while M. thermoacetica has been
extensively studied under carbon dioxide or under gas mixture
* Shiro Saka
Department of Socio-Environmental Energy Science, Graduate
School of Energy Science, Kyoto University, Yoshida-honmachi,
Sakyo-ku, Kyoto 606-8501, Japan
Appl Microbiol Biotechnol (2017) 101:6841–6847