Environmental Engineering Reference
In-Depth Information
taBle 21.4
summary of all sugarcane microarray experiments
number of differentially
expressed Genes
Platform
samples
treatment/conditions
Sugarcane nylon arrays
(1536 genes)
12
34
Cold stress-induced
Sugarcane EST nylon arrays
(1536 genes)
12
26
MeJA-induced
Affymetrix sugarcane
genome array (6024
genes)
12
119
Stem development
8
74
Leaves sugar accumulation
SUCASTv1 (2208 genes)
16
14
Phosphate starvation
8
9
Herbivory
16
13
ABA
12
42
MeJA
8
11
N
2
-ixing endophytic
12
80
Drought
36
172
Mature/Immature Internode high/low brix
16
126
Internode high/low brix 1,5,9
SUCASTv3 (1920 genes)
26
216
Six different tissues
4
24
Leaves high/low brix
SUCASTv2 (1920 genes)
28
216
Six different tissues
Source:
Gene Expression Omnibus database, http://www.ncbi.nlm.nih.gov/geo (accessed May 5, 2009).
21.9 conventIonal BIoethanol ProductIon
Because of rising oil prices and environmental concerns regarding nonrenewable fuels, ethanol has
become an alternative to gasoline for auto engines. The Brazilian Government started a program
to replace ethanol for gasoline in 1975; in 2008 the use of ethanol surpassed that of gasoline as
fuel for cars and light vehicles. Because of the flex-fuel technology that allows engines to operate
with any proportion of ethanol and gasoline, since 2008 cars that run on ethanol became dominant
in Brazil; in 2009/2010 57% of the sugarcane crushed in Brazil was used for ethanol and 43% for
sucrose (Unica 2009) and of the 413 mills operating in Brazil, 398 produce ethanol (MAPA 2009).
Except for Brazil, in most countries ethanol comprises a relatively small proportion of the sugarcane
industry output and is directed to liquor or chemical purposes; however, it is expected that the use of
ethanol as fuel will be the main driver for the expansion of sugarcane production in the world in the
near future (Figure 21.1). Presently, approximately 90% of the fuel ethanol production in the world
comes from the United States and Brazil.
Sugarcane is used for ethanol production by fermentation followed by distillation of sucrose or
molasses. The theoretical yield of ethanol is 617 L/t of sucrose but, at the normal operating condi-
tions of ethanol distilleries, the yield is usually 510-530 L/t sucrose. The average yield of ethanol
in Brazil is 82-85 L ethanol/t of fresh cane crushed (Boddey et al. 2008). Anhydrous bioethanol
production processed from sugarcane juice in an autonomous distillery is comprised by the fol-
lowing main steps: sugarcane cleaning; extraction of sugars; juice treatment, concentration and
sterilization; fermentation; distillation and dehydration; and purification as described in the fol-
lowing items.
