|
University of Minnesota Digital Conservancy >
University of Minnesota - Twin Cities >
Dissertations and Theses >
Dissertations >
Please use this permanent URL to cite or link to this item:
http://purl.umn.edu/120993
|
| Title: | Bio-fuel production by using integrated anaerobic fermentation. |
| Authors: | Xu, Lei |
| Keywords: | Clostridium sp.
Co-culture
Consolidated bioprocessing
Fermentation
Immobilization
Lignocellulosic ethanol
Bioproducts/Biosystems Science Engineering and Management
Alginate gel |
| Issue Date: | Jan-2012 |
| Abstract: | Saccharification is one of the most critical steps in producing lignocellulose-based
bio-ethanol through consolidated bioprocessing (CBP). However, extreme pH and
high ethanol concentrations are commonly considered potential inhibitors for the
application of Clostridium sp. in CBP. The fermentation of several saccharides
derived from lignocellulosics was investigated with a co-culture consisting of
Clostridium themocellum and Clostridium thermolacticum with or without
immobilization. Alkali environments proved to be more favorable for ethanol
production. Fermentation inhibition was observed at high ethanol concentrations
(>8g/L) and extreme pH (>10). However, low levels of initial ethanol addition
resulted in an unexpected stimulatory impact on the final ethanol productions for all
cultures under selected conditions. The co-culture was able to actively ferment
glucose, xylose, cellulose and micro-crystallized cellulose (MCC). The ethanol
yield observed in the co-culture was higher (up to two-fold) than in mono-cultures,
especially in MCC fermentation. The highest ethanol yield (as a percentage of the
theoretical maximum) observed were 75% (w/w) for MCC and 90% (w/w) for xylose.
Immobilization technique using sodium alginate is efficient in improve the ethanol
production during co-culture fermentation, although the immobilization is not able to
change the ethanol sensitivity of this co-culture. The ethanol yield through the use
of immobilized technique increased to 97% of the theoretical efficiency for glucose. For cellobiose and MCC under optimized condition, the ethanol yields were
approaching 85% of the theoretical efficiency. In order to examine the feasibility of
this immobilization co-culture on lignocellulosic biomass conversion, untreated and
pretreated aspen fermentations were performed. The immobilization co-culture
shows clear benefit in bio-ethanol production in CBP process. With a 3h, 9%
NaOH pretreatment, the aspen powder fermentation yield approached 78% of the
maximum theoretical efficiency, which is almost twice the yield of the untreated
aspen fermentation.
Keywords: Consolidated bioprocessing, Clostridium sp., Fermentation, Co-culture,
Lignocellulosic ethanol, Immobilization, Alginate gel. |
| Description: | University of Minnesota Ph.D. dissertation.January 2012. Major: Bioproducts/Biosystems Science Engineering and Management. Advisors:Ulrike Tschirner, Jonathan Schilling. 1 computer file (PDF); xi, 183 pages. |
| Permanent URL: | http://purl.umn.edu/120993 |
| Appears in Collections: | Dissertations
|
Files in This Item:
| File |
Description |
Size | Format |
|---|
| Xu_umn_0130E_12546.pdf | | 1013Kb | PDF | View/Open |
|
Items in the Digital Conservancy are protected by copyright, with all rights reserved, unless otherwise indicated.
|
