Progress in Second Generation Ethanol Production with Thermophilic Bacteria

Thermophilic bacteria have gained increased attention as prospective organisms for bioethanol production from lignocellulosic biomass due to their broad substrate spec tra including many of the hexoses pentoses, and disaccharides found in biomass and biomass hydrolysates, fast growth rates, and high tolerance for extreme cultivation con -ditions. Apart from optimizing the ethanol production by varying physiological param - eters, genetic engineering methods have been applied. This review focuses upon those thermophilic anaerobes recognized as being highly ethanologenic, their metabolism, and the importance of various culture parameters affecting ethanol yields, such as the partial pressure of hydrogen, pH, substrate inhibition, and ethanol tolerance. Also, recent devel - opments in evolutionary adaptation and genetic engineering of thermophilic anaerobes are addressed.