evaluated the alleviation of the inhibitors. C. ligniaria NRRL30616 was an ideal
candidate identified by (Nichols 2005). It is considered ideal because it had increased
tolerance to inhibitory compounds and could metabolize these inhibitors (mainly
furans and acetate) as a carbon source and energy. C. ligniaria can be used to reduce
the inhibitors that are formed during diluted acid, pretreatment of different biomass,
such as switchgrass, reed canary grass, alfalfa stem, corn stover, and rice hull,
resulting in confirmation, ethanol productions with a short lag phase (Nichols et al.
2010). To improve the ethanol production by a recombinant bacterium, Escherichia
coli FBR5E, we can use the C5 sugars such as pentose and arabinose in the
biologically detoxified hydrolysates with C. ligniaria. This strain of E. coli can
ferment both C5 and C6 sugars, but we cannot use it in the presence of the pretreated
hydrolysates due to its sensitivity to inhibitory compounds (furfural, HMF, and
acetic acid). The FBR5 strain of E. coli could consume both C5 and C6 sugars,
when the diluted acid pretreated and detoxified corn stover hydrolysates were used
as a substrate for microbial fermentation, but could not in the non-biologically
detoxified hydrolysates (Nichols et al. 2008). Detoxification in the liquid hot water
pretreated corn stover hydrolysate is another example that showed the best cellulose
conversion to glucose by the combination of biological detoxification followed by
maleic acid or activated charcoal plus enzyme treatment (Kim et al. 2016).
5.8 Drawbacks of Biological Method
It is time-consuming and more time is consumed in microbial growth. And this
growth as a result can affect sugars. Currently, 1070 oxidoreductase, 926 dehydrogenases, 227 decarboxylases, and 23 genes related to oxidative stress are found in
the first genome of C. ligniaria. These achievements can prove very beneficial in the
coming genetic and metabolic engineering (Duque et al. 2015).
5.8.1 Adaptation of Microbes
Many of the inhibitory components like that of hydrolysate samples interact with the
microbes so that arises the evolution of that treated microbe. In the fermentation
process whenever a treated microbe with an inhibitory component is applied, it
modifies microbe that becomes highly endurable to the organic molecules like
aldehydes, benzene components, etc.; these organic components had a great impact
on yield (Almario et al. 2013). The genetically modified strains of S. cervisiae
effectivily utilized the pretreated bagasse hydrolysates and gave better yield. The
high yield and productivity was due to the availability of sugars from biomass. Due
to this modified strain used in the fermentation makes the process fast but the final
product is quite similar to that strain which is not modified (Martín et al. 2007). This
revolutionized that the most evolved modified microorganism increase the
5 Challenges in Bioethanol Production: Effect of Inhibitory Compounds
143
candidate identified by (Nichols 2005). It is considered ideal because it had increased
tolerance to inhibitory compounds and could metabolize these inhibitors (mainly
furans and acetate) as a carbon source and energy. C. ligniaria can be used to reduce
the inhibitors that are formed during diluted acid, pretreatment of different biomass,
such as switchgrass, reed canary grass, alfalfa stem, corn stover, and rice hull,
resulting in confirmation, ethanol productions with a short lag phase (Nichols et al.
2010). To improve the ethanol production by a recombinant bacterium, Escherichia
coli FBR5E, we can use the C5 sugars such as pentose and arabinose in the
biologically detoxified hydrolysates with C. ligniaria. This strain of E. coli can
ferment both C5 and C6 sugars, but we cannot use it in the presence of the pretreated
hydrolysates due to its sensitivity to inhibitory compounds (furfural, HMF, and
acetic acid). The FBR5 strain of E. coli could consume both C5 and C6 sugars,
when the diluted acid pretreated and detoxified corn stover hydrolysates were used
as a substrate for microbial fermentation, but could not in the non-biologically
detoxified hydrolysates (Nichols et al. 2008). Detoxification in the liquid hot water
pretreated corn stover hydrolysate is another example that showed the best cellulose
conversion to glucose by the combination of biological detoxification followed by
maleic acid or activated charcoal plus enzyme treatment (Kim et al. 2016).
5.8 Drawbacks of Biological Method
It is time-consuming and more time is consumed in microbial growth. And this
growth as a result can affect sugars. Currently, 1070 oxidoreductase, 926 dehydrogenases, 227 decarboxylases, and 23 genes related to oxidative stress are found in
the first genome of C. ligniaria. These achievements can prove very beneficial in the
coming genetic and metabolic engineering (Duque et al. 2015).
5.8.1 Adaptation of Microbes
Many of the inhibitory components like that of hydrolysate samples interact with the
microbes so that arises the evolution of that treated microbe. In the fermentation
process whenever a treated microbe with an inhibitory component is applied, it
modifies microbe that becomes highly endurable to the organic molecules like
aldehydes, benzene components, etc.; these organic components had a great impact
on yield (Almario et al. 2013). The genetically modified strains of S. cervisiae
effectivily utilized the pretreated bagasse hydrolysates and gave better yield. The
high yield and productivity was due to the availability of sugars from biomass. Due
to this modified strain used in the fermentation makes the process fast but the final
product is quite similar to that strain which is not modified (Martín et al. 2007). This
revolutionized that the most evolved modified microorganism increase the
5 Challenges in Bioethanol Production: Effect of Inhibitory Compounds
143