PretreatmentLignocellulose is prepared to increase cellulose hydrolysation rate and minimise inhibitor formation. For example, increase surface area available to enzyme lets the more reaction to occur at the same time. Feedstock characteristics determine the treatment type.
Agricultural residues benefit from:
- Ammonia fibre freeze explosion,
- Lime or calcium hydroxide,
- Alkali or sodium hydroxide, or
- Steam explosion.
Cellulases break β-1-4-glycosidic glucan bonds. Aerobic filamentous fungi such as T. reesei produces cellulose system for industrial use.
Fermenting MicroorganismsThe species requirements are:
- High ethanol yield
- High productivity
- Withstand high ethanol concentration
- Xylose fermenting yeasts e.g. Candida shehata,
- Bacteria such as Zymomonas mobilis and E. coli.
- Engineered S. cerevisiae and E. coli.
|Bakers Yeast Characteristics||Value|
|Yield||0.45 g g-1|
|Specific Growth Rate||1.3 g g-1 cell mass h-1|
|Ethanol Tolerance||100 g L-1|
Process OptimisationThe scientist manipulated the following conditions:
- Substrate loading
- Enzyme loading
- Yeast loading
Olofsson, K., Bertilsson, M & Liden, G. (2008). A short review on SSF – an interesting process option for ethanol production from lignocellulosic feedstocks. Biotechnology for Biofuels, 1(7). DOI:10.1186/1754-6834-1-7