Improving volumetric hydrogen production by using immobilization methods in a modified continuous stirred tank reactor
(2019) MOBN03 20182Degree Projects in Molecular Biology
- Abstract
- Hydrogen is a very alluring source of energy and new sources of hydrogen production via sustainable and clean sources is of high priority. Dark fermentation has the potential to be this new sustainable clean source of hydrogen but requires profound optimization. Caldicellulosiruptor is a genus of thermophilic bacteria that is capable of producing hydrogen near the stoichiometric limits of 4 mol / mol hexose while using waste from paper industries, palm oil refining effluents etc. The drawbacks of this organism are the low volumetric H2 production due to growing only in low cell densities and low tolerance to high sugar concentrations. In this study, an attempt to decouple cell growth rate from dilution rate in chemostat cultures by... (More)
- Hydrogen is a very alluring source of energy and new sources of hydrogen production via sustainable and clean sources is of high priority. Dark fermentation has the potential to be this new sustainable clean source of hydrogen but requires profound optimization. Caldicellulosiruptor is a genus of thermophilic bacteria that is capable of producing hydrogen near the stoichiometric limits of 4 mol / mol hexose while using waste from paper industries, palm oil refining effluents etc. The drawbacks of this organism are the low volumetric H2 production due to growing only in low cell densities and low tolerance to high sugar concentrations. In this study, an attempt to decouple cell growth rate from dilution rate in chemostat cultures by immobilization of co-cultures of C. kronotskyensis and C. owensensis was made. This was coupled with the estimation of the population dynamics in the co-culture in both the planktonic and biofilm phases, by designing probes for quantitative PCR to reliably differentiate four species of this genus. Thus, when a substrate for attachment was provided, C. owensensis is the dominant population accounting for more than 99 % of the biomass in the co-culture. However, pure cultures of C. kronotskyensis in the presence of a substrate for attachment could also improve the volumetric H2 production (QH2), which suggests that co-cultures may not be required as previously thought.
An elucidation of sugar uptake characteristics of C. kronotskyensis was also undertaken. An initial analysis revealed that C. kronotskyensis most likely has a competitive uptake system for at least xylose and glucose where a single transporter is responsible for uptake of both sugars. (Less) - Popular Abstract
- Improving total biohydrogen output of extreme thermophile Caldicellulosiruptor by optimizing bioreactor design to facilitate cell retention
Hydrogen as a fuel source does not produce any environmental damage but the sources of hydrogen in the present day rely on highly contaminating processes such as coal and petroleum industries. Hydrogen is also an essential component for fertilizer production and oil refining, generating a gross revenue of US$115 billion in 2017. Thus, it is of vital importance to find clean and alternative sources for hydrogen.
Species of the extreme thermophilic Caldicellulosiruptor are gram-positive bacteria that can degrade waste from paper mills, palm oil industries etc., and produce hydrogen at close to 4... (More) - Improving total biohydrogen output of extreme thermophile Caldicellulosiruptor by optimizing bioreactor design to facilitate cell retention
Hydrogen as a fuel source does not produce any environmental damage but the sources of hydrogen in the present day rely on highly contaminating processes such as coal and petroleum industries. Hydrogen is also an essential component for fertilizer production and oil refining, generating a gross revenue of US$115 billion in 2017. Thus, it is of vital importance to find clean and alternative sources for hydrogen.
Species of the extreme thermophilic Caldicellulosiruptor are gram-positive bacteria that can degrade waste from paper mills, palm oil industries etc., and produce hydrogen at close to 4 mol/ mol hexose sugar, which is the stoichiometric limit of biohydrogen production via anaerobic fermentation. The issue is that thermophilic bacteria grow only to low cell densities and are extremely sensitive to high concentrations of sugar. This project aimed at addressing the issue of low cell densities by biofilm formation, which is a way to increase cell densities.
Continuous stirred tank bioreactors were modified by the addition of a cage made of stainless steel to accommodate acrylic wool that acts as a substrate of attachment for co-cultures of Caldicellulosiruptor sp.. Chitosan (a de-acetylated form of chitin) is used as an inducer of biofilm formation by cell aggregation.
Total hydrogen production was improved by a factor close to 2 reaching 29 mmol/L/h hydrogen. This opens new doors and incentives for future research in the field of biological hydrogen production by anaerobic fermentation as we are a step closer to an economically feasible method for fuel generation as well as waste management. Future prospects involves improving fermentor design tailor made to reduce hydrogen partial pressures within the bioreactor to further increase specific hydrogen productivity along with total hydrogen production.
Master’s Degree Project in Molecular Biology specializing in Microbiology 60 credits 2019
Department of Biology, Lund University
Advisor: Ed van Niel
Department of Applied Microbiology, LTH, Lund University. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/8989837
- author
- Sreenivas, Krishnan
- supervisor
-
- Ed van Niel LU
- organization
- course
- MOBN03 20182
- year
- 2019
- type
- H2 - Master's Degree (Two Years)
- subject
- language
- English
- id
- 8989837
- date added to LUP
- 2019-07-03 16:01:39
- date last changed
- 2019-07-03 16:01:39
@misc{8989837,
abstract = {{Hydrogen is a very alluring source of energy and new sources of hydrogen production via sustainable and clean sources is of high priority. Dark fermentation has the potential to be this new sustainable clean source of hydrogen but requires profound optimization. Caldicellulosiruptor is a genus of thermophilic bacteria that is capable of producing hydrogen near the stoichiometric limits of 4 mol / mol hexose while using waste from paper industries, palm oil refining effluents etc. The drawbacks of this organism are the low volumetric H2 production due to growing only in low cell densities and low tolerance to high sugar concentrations. In this study, an attempt to decouple cell growth rate from dilution rate in chemostat cultures by immobilization of co-cultures of C. kronotskyensis and C. owensensis was made. This was coupled with the estimation of the population dynamics in the co-culture in both the planktonic and biofilm phases, by designing probes for quantitative PCR to reliably differentiate four species of this genus. Thus, when a substrate for attachment was provided, C. owensensis is the dominant population accounting for more than 99 % of the biomass in the co-culture. However, pure cultures of C. kronotskyensis in the presence of a substrate for attachment could also improve the volumetric H2 production (QH2), which suggests that co-cultures may not be required as previously thought.
An elucidation of sugar uptake characteristics of C. kronotskyensis was also undertaken. An initial analysis revealed that C. kronotskyensis most likely has a competitive uptake system for at least xylose and glucose where a single transporter is responsible for uptake of both sugars.}},
author = {{Sreenivas, Krishnan}},
language = {{eng}},
note = {{Student Paper}},
title = {{Improving volumetric hydrogen production by using immobilization methods in a modified continuous stirred tank reactor}},
year = {{2019}},
}