Submitted to: Irish Journal of Agricultural Research
Publication Type: Review article
Publication Acceptance Date: 12/31/1995
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Technologies which can produce fuel ethanol from lignocellulose are currently available. The challenge is to assemble these technologies into a commercial demonstration plant while mounting a vigorous research and development program to provide incremental improvements. Bacteria such as Escherichia coli strain K011 have been specifically engineered to produce ethanol at greater than 90% of theoretical yield (40 g ethanol/L in 48-72 h) from all of the sugar constituents in hemicellulose (pentoses and hexoses). Methods have been developed to produce hemicellulose syrups containing high concentrations of sugars and to ameliorate toxins created during hydrolysis. The effectiveness of strain K011 has been demonstrated with hemicellulose hydrolysate (industrial nutrients) at the 150-liter scale and with laboratory sugar at the 10,000-liter scale. Additional organisms such as Klebsiella oxytoca strain P2 have been engineered specifically for the simultaneous saccharification and fermentation of cellulose (SSF). The purchase of cellulase is one of the major costs associated with all SSF processes. The new organisms eliminate the need for added cellobiase and, in some cases, produce part of the endoglucanase. Strain P2 has been tested with bagasse, purified cellulose and mixed waste office paper. The requirement for cellulase was quite low and was further reduced using a novel method for enzyme recycling. With recycling, ethanol yields were predicted to be over 539 liters per metric ton. With onsite production, the estimated cost of cellulase for this process is 8.5 cents (U.S.) per liter.