Isolation of Xylose Fermentation Strains for Ethanol Production and Xylose Fermentation Research

As a clean and renewable source of energy, ethanol is a promising alternative to fossil fuels.1 Especially lignocelluloses, as raw material for ethanol production, have gained great interest during these years.2 Production of bio-ethanol will help to cope with the over-consumption of fossil fuels and further work for the reduction of carbon dioxide emissions. Lignocelluloses (crop residue, cellulose waste, municipal solid waste, and so on) as raw material, cost less than starches, thus, larger quantities are acquirable, permitting large-scale production.3 Lignocellulose materials can be found everywhere in the world, and utilization makes use of waste. During the ethanol fermentation process, lignocellulose materials are hydrolyzed by acids and enzymes. Dilute-acid hydrolysis is a common but good method to quickly produce sugars form lignocelluloses.4–6 Xylose is the major product of the hydrolysis of hemicellulose from many plant materials. Corn straw, as a plant material, contains two main types of polymers, cellulose and hemicellulose, whose conversion into fermentable sugars is easy. The hydrolyzates of corn straw are composed of xylose, hexose, and other hydrolysis byproducts. Hexose is easily fermented to ethanol but xylose is more difficult to ferment. Xylose utilization is important for successful lignocellulose-ethanol fermentation.7 Xylose is abundant in lignocellulosic biomass such as corn stover,8 and forest industry waste.9 The fermentation of xylose is still a key problem in cellulose ethanol fermentation. Successful utilization of xylose could improve the efficiency of the biomass-ethanol fermentation process. A number of attempts have been made in obtaining a stable microorganism capable of utilizing xylose. It was reported that several xylose fermentation strains had been separated, such as Pichia stipites,10 Candida shehatae,11 Pachysolen tannophilus,12 some genetically engineered xylose-fermenting yeast13 and so on. However, these fermentation strains are relatively poor fermentative microorganisms. And the influIsolation of Xylose Fermentation Strains for Ethanol Production and Xylose Fermentation Research