The efficiency of cellulose hydrolysis under straight saccharification and
simultaneous saccharification and fermentation (SSF) conditions was evaluated using three
lignocellulosic materials (switchgrass, cornstover, and poplar), which had been pretreated
with dilute sulfuric acid under conditions which optimized xylose concentrations in the
prehydrolysate liquid. Yields of glucose, cellobiose and ethanol obtained from the
pretreated feedstocks were measured over 168 hrs. The final theoretical conversions of
cellulose from pretreated switchgrass, cornstover, and poplar in straight saccharification
were 85-100% (average 94%), 84-100% (average 96%), and 75-100% (average 87%),
respectively, while in SSF the conversions were 84-90% (average 87%), 91-96% (average
90%), 72%-82% (average 76%), respectively. The conversion rates of poplar in straight
saccharification and SSF were significantly lower than those of switchgrass and
cornstover. The effects of reaction parameters such as enzyme activity, cellulose
availability, and yeast cell viability on the extent of hydrolysis in straight saccharification and SSF were also studied. Results indicate that the lower glucose or ethanol yields
associated with some of the poplar were due to the recalcitrant nature of its cellulose.
To compare accurately the efficiencies between straight saccharification and SSF,
a direct method for determining the cellulose content of the feedstocks residues resulting
from SSF experiments has been developed and evaluated. The method improves on
classical cellulose assays by incorporating a yeast lysing enzyme to remove yeast glucans
from the feedstocks residue prior to acid hydrolysis and subsequent quantification of
cellulose derived glucose. A freeze-drying step was identified as necessary to render the
SSF yeast cells susceptible to enzyme lysis. The method was applied to the analysis of the
cellulose and yeast-glucan content of SSF residues from the three pretreated feedstocks.
Cellulose assays employing the lysing enzyme preparation demonstrated relative errors up
to 7.2% when yeast-associated glucan were not removed prior to analysis of SSF residues.
Enzymatic lysis of SSF yeast cells may be viewed as a general preparatory procedure to be
used prior to the subsequent chemical and physical analysis of SSF residues. / Graduation date: 1996
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/27186 |
| Date | 30 May 1996 |
| Creators | Chung, Yun-Chin |
| Contributors | Penner, Michael H. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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