unproductive adsorption of enzymes to other molecules hence improve the enzymatic hydrolysis of pretreated hardwood. When pre-culture with bovine serum
albumin was done at 50 mg/g solids prior to enzyme digestion resulted in giving
90% conversion yield (Kim et al. 2015). Only 30% yield was obtained in control.
The lignin effect was studied more and it revealed, as enzyme activity decreased and
lignin to exposed enzyme ratio was increased, a very noticeable enzyme inhibition
was seen. It was mainly due to the nonproductive binding of enzyme to lignin
(Ko et al. 2015). In the release of strong lignin and lignin-derived compounds the
major contributor is severity factor of pretreatment, which could be more severe to
enzyme activities. For example, 1% (w/v) lignin-free cellulose conversion in presence of 0.5% isolated lignin at 8 mg enzyme protein/g glucan resulted in giving 58%
product but when the isolated lignin from higher severity factors of log
R0 ¼ 11.39–12.51 was added, the cellulose conversion to glucose was fallen by
51%. Activated carbon is also very useful in binding and sequestering of many furan
derivatives, acetic acid, and phenolics in the slurry. Particularly, activated carbon can
remove all phenolics efficiently. Recent work concluded that most of the phenolics
were reduced from 132 AU to 8 AU after treatment with activated carbon (Kim et al.
2016). It is in the chemical property of carbon that it can absorb soluble hexose and
pentose that results in loss of fermentable sugars (Kim et al. 2013). Aghazade et al.
demonstrated in their another attempt that liquid-liquid extraction LLE was able to
extract 90% acetic acid, using ethyl acetate solvent that gave 11% higher ethanol
yield. This method is not favorable for industries as it requires additional solvent
supplements and extraction processes, it provides a new scalable technique and
protocol to alleviate inhibitory compounds in pretreated lignocellulosic masses.
The main challenge with implementing a detoxification approach is that these protocols require an additional independent step that may rise the concern of capital
evaluation. Cellulose ethanol production is currently available around $2.5/gallon
according to recent techno-economic analysis.
Ethanol production properties are acid pretreatment, simulation with different
agricultural feedstocks, detoxification with activated carbon, enzyme hydrolysis
fermentation with pichia stipites and S. cerevisiae and distillation (Duque et al.
2015).
5.7.2 Biological Detoxification
For the implementation of a detoxification process, which is an environment friendly
way, we can use harsh chemicals and expensive processing materials that will help in
avoiding energy-intensive processing conditions. During this process,
lignocellulosic-derived inhibitors could be alleviated or eliminated before enzymatic
hydrolysis and fermentation by microorganism pretreatment (Cannella et al. 2014;
Cao et al. 2015). Prior to enzyme digestion and microbial fermentation, several
microorganisms, such as Coniochaeta ligniaria, Paecilpmyces variotii, Urebacillus
thermosphaericus, and genetically modified S. cerevisiae were suggested and
142
FaizaKausar et al.
albumin was done at 50 mg/g solids prior to enzyme digestion resulted in giving
90% conversion yield (Kim et al. 2015). Only 30% yield was obtained in control.
The lignin effect was studied more and it revealed, as enzyme activity decreased and
lignin to exposed enzyme ratio was increased, a very noticeable enzyme inhibition
was seen. It was mainly due to the nonproductive binding of enzyme to lignin
(Ko et al. 2015). In the release of strong lignin and lignin-derived compounds the
major contributor is severity factor of pretreatment, which could be more severe to
enzyme activities. For example, 1% (w/v) lignin-free cellulose conversion in presence of 0.5% isolated lignin at 8 mg enzyme protein/g glucan resulted in giving 58%
product but when the isolated lignin from higher severity factors of log
R0 ¼ 11.39–12.51 was added, the cellulose conversion to glucose was fallen by
51%. Activated carbon is also very useful in binding and sequestering of many furan
derivatives, acetic acid, and phenolics in the slurry. Particularly, activated carbon can
remove all phenolics efficiently. Recent work concluded that most of the phenolics
were reduced from 132 AU to 8 AU after treatment with activated carbon (Kim et al.
2016). It is in the chemical property of carbon that it can absorb soluble hexose and
pentose that results in loss of fermentable sugars (Kim et al. 2013). Aghazade et al.
demonstrated in their another attempt that liquid-liquid extraction LLE was able to
extract 90% acetic acid, using ethyl acetate solvent that gave 11% higher ethanol
yield. This method is not favorable for industries as it requires additional solvent
supplements and extraction processes, it provides a new scalable technique and
protocol to alleviate inhibitory compounds in pretreated lignocellulosic masses.
The main challenge with implementing a detoxification approach is that these protocols require an additional independent step that may rise the concern of capital
evaluation. Cellulose ethanol production is currently available around $2.5/gallon
according to recent techno-economic analysis.
Ethanol production properties are acid pretreatment, simulation with different
agricultural feedstocks, detoxification with activated carbon, enzyme hydrolysis
fermentation with pichia stipites and S. cerevisiae and distillation (Duque et al.
2015).
5.7.2 Biological Detoxification
For the implementation of a detoxification process, which is an environment friendly
way, we can use harsh chemicals and expensive processing materials that will help in
avoiding energy-intensive processing conditions. During this process,
lignocellulosic-derived inhibitors could be alleviated or eliminated before enzymatic
hydrolysis and fermentation by microorganism pretreatment (Cannella et al. 2014;
Cao et al. 2015). Prior to enzyme digestion and microbial fermentation, several
microorganisms, such as Coniochaeta ligniaria, Paecilpmyces variotii, Urebacillus
thermosphaericus, and genetically modified S. cerevisiae were suggested and
142
FaizaKausar et al.