Environmental Engineering Reference
In-Depth Information
Starch
Sugars
Enzymatic hydrolysis
Breakdown into
glucose/fructose
Microbial
fermentation
Bio-ethanol
FIGure 29.1
Flowchart showing stepwise procedure involved in the production of bioethanol from sugar
and starch components of sugarbeet.
physiological characters of importance related to crop productivity. Agronomic performance of
different sugarbeet varieties and germplasm accession at different locations should also be evaluated
to identify varieties adapted to a particular area (Sarwar et al. 2008). Efforts should be given to
create a genetic map of the crop species, which will help in advocating better breeding programs
focused on crop improvement. Sugarbeet improvement could be aided by identifying quantitative
trait loci (QTL) linked to simple sequence repeats (SSRs), random amplified polymorphic DNA
(RAPD), expressed sequence tags (ESTs), or amplified fragment length polymorphism (AFLP)
markers. Schnedier et al. (2001) identified 21 different QTL associated with sugar content, sugar
and beet yield, and amino-nitrogen content in sugarbeet verified at six locations. Further, targeted
induced local lesion in genomes (TILLING) should also be undertaken to identify mutants with
increased productivity, less canopy area, and decreased days to maturity. Other approaches may
include targeted reduction of genes by RNA interference (RNAi) and micro-RNA, which may
increase productivity and reduce diversion of photoassimilates toward noneconomic parts of the
plants [i.e., vegetative parts particularly genes involved in gibberellin (GA) metabolism]. Also,
identification and ectopic expression of transgenes should also be considered. Therefore, cloning
genes responsible for rapid conversion of sugars (dextrose, raffinose, and sucrose) to ethanol (Atiyeh
and Duvnjak 2003b) and then expression of such genes in a plant system will enhance the production
of ethanol.
Smith (2008) reported that manipulation of ADP-glucose pyrophosphorylase, which plays a
role in the sugar signaling pathway, to increase the yields of starch have been met with limited
success. One of the aspects for biofuel production is synchronous maturity of the crops used
for biofuel production. Many chemicals that promote synchronous maturity such as napthalene
acetic acid (NAA) could be useful. Also, application of gibberelic acid (GA) may result in high
yield. Anti-GA substances such as pacrobutrazol can be used to control plant height, or ectopic
expression of GA 2-oxidase will result in dwarf plants (Dijkstra et al. 2008). This will allow for
easy harvest of the produce with low cost on resources and saving time. Compact plants are also
less prone to damage by biotic and abiotic stresses. Several research groups including researchers
from the United Kingdom have concentrated their efforts on controlling stature and flowering in
sugarbeet at Boomsbarn, Rothamsted Research, England (Mutasa-Gottgens et al. 2008). Other
