The production of ethanol from lignocellulose offers many potential opportunities for

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Table III. Comparison of SSF Results for Different Substrates and Biocatalysts

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Strain P2 — Enzyme Recycle

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Figure 6. Comparison of ethanol production from waste office paper (MWOP) by K. oxytoca strain P2 and yeast. More detail concerning fermentation conditions and references are provided in Table III.

synergy with other types of manufacturing processes. Perhaps the simplest of these would involve a combination of electricity with boilers fired from the residues after hemicellulose hydrolysis and ethanol production from hemicellulose syrups. This process could reduce heavy metal contamination of boiler feeds derived from municipal landfill waste (metals precipitated with the gypsum) and upgrade thermal value. Low grade steam could be used for ethanol purification and other processes.

Cane sugar production plants could also benefit from increased ethanol yields by fermenting hemicellulose syrups, analogous to the conversion of bagasse to furfural plant in south Florida. Although bagasse is burned to power sugar refining, excess bagasse typically accumulates. Hemicellulose could be stripped by dilute acid hydrolysis and fermented to ethanol, leaving sufficient residue as a boiler fuel for both processes.

Ethanol production from grain and cane sugar offer an extremely attractive opportunity for synergy. Spent yeasts from these processes could be recycled as a nutrient source for hemicellulose or cellulose fermentations. Com fiber residues, com cobs, com stover, bagasse or other lignocellulosic residues could serve as a feedstock for the biomass to ethanol process. Again, undigested residues could be burned to provide the energy.

Acknowledgments

This research was supported in part by the Florida Agricultural Experimental Station (publication number R-05323) and by grants from the U. S. Department of Agriculture, National Research Initiative (95-37308-1843) and the U. S. Department of Energy, Office of Basic Energy Science (DE-FG02-96ER20222).