Influence of pH Regulation Mode in Glucose Fermentation on Product Selection and Process Stability.
Mixed culture anaerobic fermentation generates a wide range of products from simple sugars, and is potentially an effective process for producing renewable commodity chemicals. However it is difficult to predict product spectrum, and to control the process. One of the key control handles is pH, but the response is commonly dependent on culture history. In this work, we assess the impact of pH regulation mode on the product spectrum. Two regulation modes were applied: in the first, pH was adjusted from 4.5 to 8.5 in progressive steps of 0.5 and in the second, covered the same pH range, but the pH was reset to 5.5 before each change. Acetate, butyrate, and ethanol were produced throughout all pH ranges, but there was a shift from butyrate at pH < 6.5 to ethanol at pH > 6.5, as well as a strong and consistent shift from hydrogen to formate as pH increased. Microbial analysis indicated that progressive pH resulted in dominance by Klebsiella, while reset pH resulted in a bias towards Clostridium spp., particularly at low pH, with higher variance in community between different pH levels. Reset pH was more responsive to changes in pH, and analysis of Gibbs free energy indicated that the reset pH experiments operated closer to thermodynamic equilibrium, particularly with respect to the formate/hydrogen balance. This may indicate that periodically resetting pH conforms better to thermodynamic expectations.
Faculty of Civil Engineering, Universiti Teknologi MARA (Pulau Pinang), 13500 Permatang Pauh, Pulau Pinang, Malaysia. cezuhaida@ppinang.uitm.edu.my.
Zuhaida
Z
Mohd-Zaki
Institute Center for Energy (iEnergy), Masdar Institute of Science and Technology, 54224 Abu Dhabi, United Arab Emirates. jbastidas@masdar.ac.ae.
Juan R
JR
Bastidas-Oyanedel
Advanced Water Management Centre, The University of Queensland, St. Lucia, QLD 4072, Australia. y.lu@awmc.uq.edu.au.
Yang
Y
Lu
Advanced Water Management Centre, The University of Queensland, St. Lucia, QLD 4072, Australia. r.hoelzle@awmc.uq.edu.au.
Robert
R
Hoelzle
Advanced Water Management Centre, The University of Queensland, St. Lucia, QLD 4072, Australia. s.pratt@uq.edu.au.
Steven
S
Pratt
Advanced Water Management Centre, The University of Queensland, St. Lucia, QLD 4072, Australia. frances.r.slater@gmail.com.
Fran R
FR
Slater
Advanced Water Management Centre, The University of Queensland, St. Lucia, QLD 4072, Australia. d.batstone@awmc.uq.edu.au.
Damien J
DJ
Batstone
fermentation; glucose; mixed culture; pH control; pH regulation method
Curr Opin Biotechnol. 2014 Jun;27:142-9
24534620
Biotechnol Bioeng. 2008 Aug 15;100(6):1088-98
18553403
Water Sci Technol. 2011;64(3):760-5
22097058
J Biotechnol. 2004 May 27;110(2):143-57
15121334
Arch Microbiol. 1983 Jan;134(1):80-5
6347115
Can J Microbiol. 2011 Mar;57(3):236-43
21358765
Appl Biochem Biotechnol. 2004 Feb;112(2):79-90
14981283
Appl Environ Microbiol. 1998 Feb;64(2):795-9
9464425
Bioresour Technol. 2002 Mar;82(1):87-93
11858207
Biotechnol Bioeng. 2014 Nov;111(11):2139-54
24980940
PLoS One. 2015 May 18;10 (5):e0126739
25992959
Appl Microbiol Biotechnol. 2008 Oct;80(6):1121-30
18800185
J Appl Microbiol. 1997 Aug;83(2):166-74
9281820
Environ Sci Technol. 2005 Dec 1;39(23):9351-6
16382963
Biotechnol Bioeng. 1997 Jun 5;54(5):428-33
18634135
Appl Environ Microbiol. 1985 Apr;49(4):733-6
4004207
Curr Opin Biotechnol. 2007 Jun;18(3):207-12
17509864
Bioresour Technol. 2007 Jul;98(9):1774-80
16935495
Talanta. 2010 Dec 15;83(2):482-92
21111163
Biotechnol Bioeng. 2007 Sep 1;98(1):69-79
17657773
Bioresour Technol. 2002 May;82(3):209-13
11991067
Appl Environ Microbiol. 1989 Dec;55(12):3131-9
16348075