Page 67 - Advances in bioenergy (2016)

through a combination of technologies. Ideally, a biorefinery should integrate biomass
conversion processes to produce a range of fuels, power, materials, and chemicals from
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biomass. Lately, a trend toward high value, lower volume bio-based chemicals has been
exhibited, aiming at the increase of the overall cost-effectiveness of a lignocellulose-based
biorefinery. However, this trend has to face two major challenges to become really applicable

and efficient in large scale: (1) The bio-based chemical production is challenged by a lack of
conversion technology; and (2) the bio-based chemical production is challenged by an
overabundance of targets. 70

Figure 2.3 Microbial conversion of glucose to ethanol under anaerobic conditions. The
enzymes catalysing the main biochemical steps are indicated. Most microorganisms catabolize
glucose through the glycolytic pathway (EMP). Although there are many aerobic bacterial
species that use the ED pathway, Zymomonas is the only known microbial genus that uses this
pathway under anaerobic conditions. LFP, pyruvate formate lyase; LDH, lactate
dehydrogenase; PEP: phosphoenolpyruvate; PPP, pentose phosphate pathway; DHAP,
dihydroxyacetone phosphate; KDPG, 2-keto-3-deoxy-6-phosphogluconate.