the total amount of glucose and xylose at that time. These values
were similar to those obtained by SSF in the present study except
for the amount of ethanol.
It was confirmed that xylose consumption started after depletion
of glucose in SHF as in the case of fermentation of mixture of
glucose and xylose on the synthetic medium; however, xylose
consumption did not lead to increased amounts of lactic acid. It
might be possible to say that xylose consumption had the effect of
maintaining a constant amount of lactic acid because reduction of
lactic acid was observed after depletion of xylose. We assume that,
in SSF, the amount of lactic acid after 96 h remained constant due to
the provision of xylose as xylose concentration decreased slightly at
96 h after depletion of glucose, although xylose was hardly
consumed. It was supposed that the above results were caused by
the carbon catabolite repression as in the case of the synthetic
medium. Thus, R. oryzae NBRC 5378, which was found to be the best
producer of lactic acid from xylose, might be not the most suitable
strain for the fermentation of wheat straw. However, the strain
indicated that such a metabolism mechanism as the carbon
catabolite repression occurred even in the case of the fermentation
of wheat straw.
In the present conditions, production of fumaric acid was not
detected during the course of either fermentation process, and
trace amounts of glycerol and xylitol were detected (data not
shown), which are possible by-products of xylose fermentation (8).
Therefore, it was considered that the difference in the amount of
the total amount of glucose and xylose at that time. These valueswere similar to those obtained by SSF in the present study exceptfor the amount of ethanol.It was confirmed that xylose consumption started after depletionof glucose in SHF as in the case of fermentation of mixture ofglucose and xylose on the synthetic medium; however, xyloseconsumption did not lead to increased amounts of lactic acid. Itmight be possible to say that xylose consumption had the effect ofmaintaining a constant amount of lactic acid because reduction oflactic acid was observed after depletion of xylose. We assume that,in SSF, the amount of lactic acid after 96 h remained constant due tothe provision of xylose as xylose concentration decreased slightly at96 h after depletion of glucose, although xylose was hardlyconsumed. It was supposed that the above results were caused bythe carbon catabolite repression as in the case of the syntheticmedium. Thus, R. oryzae NBRC 5378, which was found to be the bestproducer of lactic acid from xylose, might be not the most suitablestrain for the fermentation of wheat straw. However, the strainindicated that such a metabolism mechanism as the carboncatabolite repression occurred even in the case of the fermentationof wheat straw.In the present conditions, production of fumaric acid was notdetected during the course of either fermentation process, andtrace amounts of glycerol and xylitol were detected (data notshown), which are possible by-products of xylose fermentation (8).Therefore, it was considered that the difference in the amount of
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the total amount of glucose and xylose at that time. These values
were similar to those obtained by SSF in the present study except
for the amount of ethanol.
It was confirmed that xylose consumption started after depletion
of glucose in SHF as in the case of fermentation of mixture of
glucose and xylose on the synthetic medium; however, xylose
consumption did not lead to increased amounts of lactic acid. It
might be possible to say that xylose consumption had the effect of
maintaining a constant amount of lactic acid because reduction of
lactic acid was observed after depletion of xylose. We assume that,
in SSF, the amount of lactic acid after 96 h remained constant due to
the provision of xylose as xylose concentration decreased slightly at
96 h after depletion of glucose, although xylose was hardly
consumed. It was supposed that the above results were caused by
the carbon catabolite repression as in the case of the synthetic
medium. Thus, R. oryzae NBRC 5378, which was found to be the best
producer of lactic acid from xylose, might be not the most suitable
strain for the fermentation of wheat straw. However, the strain
indicated that such a metabolism mechanism as the carbon
catabolite repression occurred even in the case of the fermentation
of wheat straw.
In the present conditions, production of fumaric acid was not
detected during the course of either fermentation process, and
trace amounts of glycerol and xylitol were detected (data not
shown), which are possible by-products of xylose fermentation (8).
Therefore, it was considered that the difference in the amount of
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