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Removal of Bacterial Contamination from Bioethanol Fermentation System Using Membrane Bioreactor
University of Borås, Faculty of Textiles, Engineering and Business.ORCID iD: 0000-0001-6280-4483
Department of Environmental Sciences and Engineering, Graduate School of Science, Engineering and Technology.
University of Borås, Faculty of Textiles, Engineering and Business. (Resource Recovery)
Flemish Institute for Technological Research.
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2018 (English)In: Fermentation, Vol. 4, no 4Article in journal (Other academic) Published
Sustainable development
According to the author(s), the content of this publication falls within the area of sustainable development.
Abstract [en]

A major issue hindering efficient industrial ethanol fermentation from sugar-based feedstock is excessive unwanted bacterial contamination. In industrial scale fermentation, reaching complete sterility is costly, laborious, and difficult to sustain in long-term operation. A physical selective separation of a co-culture of Saccharomyces cerevisiae and an Enterobacter cloacae complex from a buffer solution and fermentation media at dilution rates of 0.1–1 1/h were examined using an immersed membrane bioreactor (iMBR). The effect of the presence of yeast, inoculum size, membrane pore size, and surface area, backwashing and dilution rate on bacteria removal were assessed by evaluating changes in the filtration conditions, medium turbidity, and concentration of compounds and cell biomass. The results showed that using the iMBR with dilution rate of 0.5 1/h results in successful removal of 93% of contaminating bacteria in the single culture and nearly complete bacteria decontamination in yeast-bacteria co-culture. During continuous fermentation, application of lower permeate fluxes provided a stable filtration of the mixed culture with enhanced bacteria washout. This physical selective separation of bacteria from yeast can enhance final ethanol quality and yields, process profitability, yeast metabolic activity, and decrease downstream processing costs.

Place, publisher, year, edition, pages
2018. Vol. 4, no 4
Keywords [en]
membrane bioreactor, filtration, bacterial decontamination, fermentation
National Category
Industrial Biotechnology
Research subject
Resource Recovery
Identifiers
URN: urn:nbn:se:hb:diva-15222DOI: 10.3390/fermentation4040088OAI: oai:DiVA.org:hb-15222DiVA, id: diva2:1259963
Available from: 2018-10-31 Created: 2018-10-31 Last updated: 2019-10-25Bibliographically approved
In thesis
1. Immersed flat-sheet membrane bioreactors for lignocellulosic bioethanol production
Open this publication in new window or tab >>Immersed flat-sheet membrane bioreactors for lignocellulosic bioethanol production
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The rising awareness of the environmental, economic and socio-political impacts of over-exploitation of fossil-based fuel and energy sources, have motivated the transition toward more sustainable and renewable energy sources. Lignocellulosic materials (e.g. agricultural residues) are potential candidates for sustainable bioethanol production that contributes to the replacement of fossil fuels. However, to have an economically feasible and commercialized process, issues associated with lignocellulosic bioethanol production in upstream, fermentation and downstream processing stages should be alleviated. Membrane bioreactors with their great capabilities in semi-selective separation are promising options for making a breakthrough in lignocellulosic biorefinery processes. Therefore, in this thesis, different membrane modules and immersed membrane bioreactors (iMBRs) set-ups were developed and applied to take advantage of this long-matured water and wastewater treatment technique in remediation of challenges in the lignocellulosic bioethanol production.

Thus, In order to intensify and optimize the lignocellulosic bioethanol production process, pressure-driven flat sheet microfiltration iMBRs were integrated into different processing stages. The application of a continuous iMBR led to a high ethanol productivity and yield (83% of theoretical yield) at high suspended solid content (up to 20% w/v) of wheat straw hydrolysate, and successful bacterial contamination separation from yeast (up to 93% removal). Moreover, using double-staged iMBRs for continuous hydrolysis-filtration and co-fermentation-filtration led to an effective separation of lignin-rich solids (up to 70% lignin) and sugar streams from the hydrolysate, and yeast cells from the fermentation product stream, stable long-term filtration performance (up to 264 h) at filtration flux of 21.9 l.m-2.h-1. In this thesis, filtration performance was thoroughly investigated, and effective physical fouling preventive approaches were applied to guarantee continuous bioprocessing. In addition, in order to remediate issues related to high content of inhibitors and presence of sequentially-fermented hexose and pentose saccharides in lignocellulosic fermentation, the cell-confinement approach of reverse membrane bioreactor (rMBR), which merges the benefits of iMBRs and cell encapsulation techniques, was introduced and applied in this thesis. It was observed that the high local cell density and diffusion-based mass transfer in the rMBR promoted co-utilization of sugars, and boosted cell furfural detoxification at concentrations of up to 16 g.l-1. Moreover, considering the needs of rMBR processes for cell recirculation, membrane envelope degassing, and media conditioning, a novel membrane module was designed, developed, and patented in this thesis work.

Place, publisher, year, edition, pages
Borås: Högskolan i Borås, 2019
Series
Skrifter från Högskolan i Borås, ISSN 0280-381X ; 98
Keywords
Lignocellulosic bioethanol, immersed membrane bioreactor, membrane fouling, reverse membrane bioreactor
National Category
Industrial Biotechnology
Research subject
Resource Recovery
Identifiers
urn:nbn:se:hb:diva-21668 (URN)978-91-88838-41-4 (ISBN)978-91-88838-42-1 (ISBN)
Public defence
2019-11-18, D209, University of Borås, Allégatan 1, Borås, 10:00 (English)
Opponent
Available from: 2019-10-25 Created: 2019-08-27 Last updated: 2019-10-25Bibliographically approved

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Mahboubi, AmirBulkan, GülruTaherzadeh, Mohammad J

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