Engineering Yeast for Cellulosic Ethanol Production

Review Article

Austin Chem Eng. 2015; 2(2): 1018.

Engineering Yeast for Cellulosic Ethanol Production

Tzi-Yuan Wang

Biodiversity Research Center, Taiwan

*Corresponding author: MTzi-Yuan Wang, Biodiversity Research Center, Academia Sinica, Taipei, 115, Taiwan

Received: August 11, 2015; Accepted: September 28, 2015; Published: October 06, 2015


Biofuel, the alternative energy, aims to greatly reduce the carbon emissions on earth. Cellulosic ethanol is expected to replace the first generation biofuel made by agriculture crops, such as corn. Lignocelluloses degradation and fermentation efficiencies are the main limitations. Thus, the objective of consolidated bioprocessing is to engineer a “super” yeast with multiple cellulolytic enzymes, multi-sugars consumption, thermo-tolerance, toxintolerance and efficient ethanol production. The super yeast needs to be engineered to be suitable glycosylation, highly secretable, deficient protease, stress-tolerance and ethanol assimilation for cellulosic ethanol. Omics analysis, adaptive laboratory evolution and genome editing tools would accelerate yeast engineering not only for biofuel, but also applications in other biosynthetic areas.

Keywords: Biomass; Omics; Yeast; Fermentation; Cellulosic ethanol; Synthetic biology; Genome editing


EU: European Union; CBP: Consolidated Bioprocessing; C5: Pentose; C6: Hexose; GH: Glycosyl Hydrolase; CRISPR: Clustered, Regularly Interspaced, Short Palindromic Repeats; Cas9: CRISPRAssociated Protein 9; SHF: Separate Hydrolysis and Fermentation; SSF: Simultaneous Saccharification and Fermentation; SSCF: Simultaneous Saccharification and Co-Fermentation


Alternative fuels are important materials in battling ongoing green-house effects [1,2]. The EU passed a statement that asked car manufacturers to reduce the carbon emissions of their products. Since the 1970’s, bio-ethanol has successfully been produced commercially using agriculture cultivates (especially in corn); benefits the green energy production in several food-supply countries, such as Brazil & USA. However, it enlarged the subsistence problem in other fooddeprived countries [3]. Therefore, cellulosic ethanol produced by feed stocks became the new generation biofuel. Cellulosic ethanol from non-grain plant materials is used as one of the green energy to replace the fossil fuel which causes net carbon emissions and seriously affects climate change for decades.

The basic bioprocess for cellulosic ethanol is feed stocks degradation, sugar utilization and then fermentation (Figure 1). Feedstocks are composed by the main component of lignocelluloses, including celluloses, hemicelluloses, and lignin’s. These polysaccharides could be degraded into sugars by kinds of cellulolytic enzymes. After lignocelluloses degradation, 1-2% C5 & C6 sugar mixtures (D-xylose, L-arabinose, glucose, lactose, etc) are hydrolyzed with the inhibitory compounds (acid/base, furfural, etc), formed during biomass pretreatment process. Yeast utilized these carbon sources can be further fermented and isolated in higher temperature for ethanol products.

Citation: Tzi-Yuan Wang. Engineering Yeast for Cellulosic Ethanol Production. Austin Chem Eng. 2015; 2(2): 1018. ISSN : 2381-8905