6.7.1 How Z. mobilis Is Unique
• As Z. mobilis is a facultative anaerobe but has ED pathway that is characteristic of
obligate aerobes.
• Z. mobilis has characteristic of energy uncoupled mechanism of growth for high
ethanol production.
• Z. mobilis has advantage of essential genes as pdc and adh genes for ethanol
production. The carbon diversion of this gene to other essential byproducts can be
challenging (Yang et al. 2010a, b). Although Z. mobilis can be easily modified
genetically. The genome editing tools as CRISPR-cas 9 can make Z. mobilis more
effective and sophisticated.
6.7.2 Pretreatment of Biomass
Pretreatment is conducted to remove lignin and other plant cell wall residuals so that
enzymatic activity can be done easily and plant biomass with rich cellulose and
hemicellulose can be obtained (Harmsen et al. 2010). Pretreatment of grasses and
hard woods gives potential sugar as byproducts such as xylose and arabinose so that
enzymatic hydrolysis becomes easier. The main focus of pretreatment is to improve
the consumption of lignocellulosic feedstocks and to get higher yield of ethanol.
A pretreatment approach AFEX is a physio-chemical process that involves the
use of liquid ammonia and steam explosion (high temperature and pressure) (Bals
et al. 2011). Another widely used pretreatment approach is DA pretreatment. It is
beneficial as it is cost effective (Mathew et al. 2016). As compared to DA, AFEX
requires higher energy requirement and use of liquid ammonia makes it costly
approach but AFEX gives less inhibitor formation and more yield is obtained with
less sugar consumption (Harmsen et al. 2010).
6.7.3 Biomass Feedstocks
The feedstock grain and corn give the starch based carbon sources. Besides lignocellulosic feedstocks other energy crops as sugar beet, sweet potato, sweet sorghum,
and sugar cane can be used (Behera et al. 2012; He et al. 2013; Yang et al. 2013). A
wide range of carbon sources can be used by Z. mobilis for ethanol production.
1. Algal biomass, e.g. biomass obtained from Spirogyra hyalina.
2. Agricultural wastes, e.g. sugar cane, molasses, waste paper sludge, and corn
residues.
3. Industrial wastes, e.g. soyabean and meal.
4. Energy crops.
5. Energy plants, e.g. switch grass.
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• As Z. mobilis is a facultative anaerobe but has ED pathway that is characteristic of
obligate aerobes.
• Z. mobilis has characteristic of energy uncoupled mechanism of growth for high
ethanol production.
• Z. mobilis has advantage of essential genes as pdc and adh genes for ethanol
production. The carbon diversion of this gene to other essential byproducts can be
challenging (Yang et al. 2010a, b). Although Z. mobilis can be easily modified
genetically. The genome editing tools as CRISPR-cas 9 can make Z. mobilis more
effective and sophisticated.
6.7.2 Pretreatment of Biomass
Pretreatment is conducted to remove lignin and other plant cell wall residuals so that
enzymatic activity can be done easily and plant biomass with rich cellulose and
hemicellulose can be obtained (Harmsen et al. 2010). Pretreatment of grasses and
hard woods gives potential sugar as byproducts such as xylose and arabinose so that
enzymatic hydrolysis becomes easier. The main focus of pretreatment is to improve
the consumption of lignocellulosic feedstocks and to get higher yield of ethanol.
A pretreatment approach AFEX is a physio-chemical process that involves the
use of liquid ammonia and steam explosion (high temperature and pressure) (Bals
et al. 2011). Another widely used pretreatment approach is DA pretreatment. It is
beneficial as it is cost effective (Mathew et al. 2016). As compared to DA, AFEX
requires higher energy requirement and use of liquid ammonia makes it costly
approach but AFEX gives less inhibitor formation and more yield is obtained with
less sugar consumption (Harmsen et al. 2010).
6.7.3 Biomass Feedstocks
The feedstock grain and corn give the starch based carbon sources. Besides lignocellulosic feedstocks other energy crops as sugar beet, sweet potato, sweet sorghum,
and sugar cane can be used (Behera et al. 2012; He et al. 2013; Yang et al. 2013). A
wide range of carbon sources can be used by Z. mobilis for ethanol production.
1. Algal biomass, e.g. biomass obtained from Spirogyra hyalina.
2. Agricultural wastes, e.g. sugar cane, molasses, waste paper sludge, and corn
residues.
3. Industrial wastes, e.g. soyabean and meal.
4. Energy crops.
5. Energy plants, e.g. switch grass.
168
M. Khalid et al.