Investigation of brewery waste grains and microbial fuel cells as value-additive technologies improving solvent production yields in Clostridium acetobutylicum (ATCC 824) fermentation
- Authors: Du Toit, Ryan Guillaume
- Date: 2023-10-13
- Subjects: Biomass energy , Butanol , Fermentation , Microbial fuel cells , Brewery waste , Clostridium acetobutylicum
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424643 , vital:72171
- Description: The production of the solvent compounds acetone, ethanol and butanol through fermentation of organic feedstocks using Clostridia species could be a promising route for biofuel production. However, the cost of raw materials, low yields and the complexity of anaerobic fermentation continue to hinder this means of generating these compounds. The research presented in this Thesis investigated low-cost interventions that could decrease the costs of production and to direct the synthesis of fuel compounds using microbial fuel cells. Low-cost anaerobic chambers were designed and constructed for the propagation and manipulation of Clostridium acetobutylicum, selected as a low-risk microbial catalyst. Fermentation was monitored using in situ pH measurements and a combination of turbidity measurements, nutrient assays (especially total carbohydrates) and HPLC-RI detection as a means of monitoring the consumption of nutrients (glucose), production of precursor compounds (butyric acid) and the formation of solvent molecules (acetone/ethanol and butanol) during fermentation by this organism. Brewer’s spent grains were tested as a sustainable and low-cost feedstock for solvent production, comparing the effects of sterilising before fermentation, or allowing resident microflora to remain during Clostridium-catalysed solvent production. Sterilised spent grains significantly improved the production of solvent molecules (e.g. 12.97 ± 0.38 g/L of butanol yielded, compared to 0.40 ± 0.33 g/L for defined media sampled during the solventogenic phase); compared to these, the use of non-sterilised brewer’s grain decreased both the reproducibility and yields of fermentation (8.66 ± 1.6 g/L of butanol). Microbial fuel cells were studied as a possible means of altering electron transfer to/from electrode-attached Clostridia to control the metabolic shift in bacteria from acidogenesis to solventogenesis. The base line MFC (11.00 ± 4.69 g/L) fermentation experiment did produce higher acetone/ethanol than the baseline batch experiment MB (5.47 ± 4.48 g/L), indicating an improvement to solvent production in C. acetobutylicum (ATCC 824) in a MFC fermentation. In this study, MFC-1 demonstrated remarkable superiority over MB in terms of butyric acid production, yielding significantly higher concentrations while also improving acetone and ethanol production. However, the enhanced butyric acid production did not correspond to significantly increased butanol yields when compared to batch fermentation of chemically defined media. These findings highlight the potential of MFC-1 as an efficient approach for enhancing the fermentative production of valuable compounds, with a particular focus on butyric acid and acetone/ethanol. , Thesis (MSc) -- Faculty of Science, Biotechnology Innovation Centre, 2023
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- Date Issued: 2023-10-13
Studies on an autolysin produced by clostridium acetobutylicum
- Authors: Webster, Jocelyn Rowena
- Date: 1981
- Subjects: Clostridium acetobutylicum , Autolysis , Bacteriocins , Proteins -- Synthesis , DNA -- Synthesis , RNA -- Synthesis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3893 , http://hdl.handle.net/10962/d1003724
- Description: An extracellular bacteriocin-like substance produced by Clostridium acetobutylicum was detected during studies on an industrial fermentation process. The bacteriocin-like substance was not inducible by either ultraviolet light or mitomycin C, and its production was not associated with the induction of a protease. Studies on the mode of action of the bacteriocin-like substance indicated that it had no significant effect on DNA, RNA, or protein synthesis, and it did not cause the loss of intracellular ATP. However, the bacteriocin-like substance was able to lyse SDS-treated cells and cell walls of C. acetobutylicum and was identified as an autolysin. Some of the characteristics of this extracellular autolysin were determined, and after purification it was shown to be a glycoprotein with a molecular weight of 28 000.
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- Date Issued: 1981
Studies on the fermentation of molasses by Clostridium acetobutylicum
- Authors: Barber, Jennifer Mary
- Date: 1978
- Subjects: Molasses , Clostridium acetobutylicum , Fermentation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4084 , http://hdl.handle.net/10962/d1007611 , Molasses , Clostridium acetobutylicum , Fermentation
- Description: The bacterium Clostridium acetobutylicum produces acetone and n [subscript] - butanol from molasses in an industrial fermentation system. Although the bacterium has been cultured in liquid media it does not grow well on agar plates and requires high concentrations of hydrogen. Pretreatment of agar plates with bovine catalase improves growth on agar media. The bacteria produce an area of clearing (halo) on Potato agar plates due to butyric acid (the precursor of n [subscript]-butanol) and ß -amylase production. This characteristic will be used as a plate screening assay for the selection of high solvent producing mutants. A laboratory scale fermentation system was developed and detailed studies including pH, turbidity and cell morphology changes, and the details of solvent production were undertaken. The fermentation was optimized for mutant selection. The production of normal solvent yields by isolated clones is required for the mutant selection programme. Studies revealed that sporulation of the clones increased their solvent yield although solvent yields were still lower than normal. Efficient sporulation is therefore a prerequisite for clone fermentation. The origin of the phage infection during the factory outbreak was determined and resistant clones obtained. The presence of a bacteriocin-like toxin causing decreases in turbidity was identified during the final fermentation stage. The strain sensitivity, optimum conditions for stability as well as the kinetics of inactivation and lethality have been investigated. Preliminary characterization and purification studies indicate the proteinaceous nature of the toxin. , KMBT_363
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- Date Issued: 1978