6.7.4 Strategies to Overcome Toxic Compounds
For greater ethanol production, strategies are employed by knowing the chemical
composition of toxic compounds and their effects on the host microbes. The
chemical components that behave as inhibitors in toxic compounds are acetate,
phenolic aldehydes, and furfural compounds (Franden et al. 2009, 2013; Wang
et al. 2014; Yi et al. 2015). In the pretreated AFEX of corn stover and switch
grass, phenolic acids and amides are the inhibitors (Keating et al. 2014; Serate
et al. 2015).
Methods adapted to lessen the toxicity of pretreated hydrolysates are
1. Deacetylation and disc refining.
2. Deacetylation and mechanical refining.
These methods overall increase the bioethanol production and reduce the toxicity
of pretreated biomass and digestibility (Chen et al. 2016). When corn stover is
fermented and DMR process is applied the ethanol titer obtained is 86 gL
À1 (Chen
et al. 2016). The second approach employed for high ethanol production is genetic
approach. Both forward genetics and reverse genetics have been used. In forward
genetics chemical mutagenesis and transposon mutagenesis are performed (Panesar
et al. 2006).
6.7.5 Strain Evaluation and Fermentation Strategies
For the purpose of strain development high throughput strain evaluation is used.
These include techniques such as Bioscreen C, Biolog’s phenotype microarrays, and
BioLector system. Biolog’s phenotype microarray gives phenotype profiling of
about 2000 Z. mobilis strains so that physiology of Z. mobilis can be studied easily
(Bochner et al. 2010). Bioscreen C system gives the advantage of studying cellular
growth of two 100 well plates at 0.4 ml scale (Table 6.4) (Franden et al. 2009; Yang
et al. 2010b).
6.8 Fermentation Systems
These are used for strain evaluation and are advantageous at both mini and micro
scales, e.g. Biolector Micro Bioreactor system. This system has various modules for
monitoring various functions and to study the different fermentation parameters as
dissolved oxygen and pH (Buchenauer et al. 2009; Funke et al. 2010; Blomberg
2011; Rohe et al. 2012). Fermentation strategies were applied depending on the
product titer and yield. Batch, fed batch, and continuous cultures can be applied
depending on the mode of application.
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169
For greater ethanol production, strategies are employed by knowing the chemical
composition of toxic compounds and their effects on the host microbes. The
chemical components that behave as inhibitors in toxic compounds are acetate,
phenolic aldehydes, and furfural compounds (Franden et al. 2009, 2013; Wang
et al. 2014; Yi et al. 2015). In the pretreated AFEX of corn stover and switch
grass, phenolic acids and amides are the inhibitors (Keating et al. 2014; Serate
et al. 2015).
Methods adapted to lessen the toxicity of pretreated hydrolysates are
1. Deacetylation and disc refining.
2. Deacetylation and mechanical refining.
These methods overall increase the bioethanol production and reduce the toxicity
of pretreated biomass and digestibility (Chen et al. 2016). When corn stover is
fermented and DMR process is applied the ethanol titer obtained is 86 gL
À1 (Chen
et al. 2016). The second approach employed for high ethanol production is genetic
approach. Both forward genetics and reverse genetics have been used. In forward
genetics chemical mutagenesis and transposon mutagenesis are performed (Panesar
et al. 2006).
6.7.5 Strain Evaluation and Fermentation Strategies
For the purpose of strain development high throughput strain evaluation is used.
These include techniques such as Bioscreen C, Biolog’s phenotype microarrays, and
BioLector system. Biolog’s phenotype microarray gives phenotype profiling of
about 2000 Z. mobilis strains so that physiology of Z. mobilis can be studied easily
(Bochner et al. 2010). Bioscreen C system gives the advantage of studying cellular
growth of two 100 well plates at 0.4 ml scale (Table 6.4) (Franden et al. 2009; Yang
et al. 2010b).
6.8 Fermentation Systems
These are used for strain evaluation and are advantageous at both mini and micro
scales, e.g. Biolector Micro Bioreactor system. This system has various modules for
monitoring various functions and to study the different fermentation parameters as
dissolved oxygen and pH (Buchenauer et al. 2009; Funke et al. 2010; Blomberg
2011; Rohe et al. 2012). Fermentation strategies were applied depending on the
product titer and yield. Batch, fed batch, and continuous cultures can be applied
depending on the mode of application.
6 Engineering of Zymomonas mobilis for Enhanced Biofuel Production
169