Dear Ahmed,

Key: try to do the calculations putting attention to detail on your dimensional analysis. That should be ok. If it doesn't troubleshoot your problem please feel free to get in touch,

good luck

There is an good diference between xylan polymer , major part also knownas hemicelulose , whic is proved to have 5 carbon , pentoses , this being xylose as manomer where as hexosan are 6C , glucose , fructuse or galactoses which can have 6carbon , all are carbohydrates polimer derived sugars, Thus the yield can be correct , yet there is error in the questiin as the basis is not hexoses , but xyloses , , see the reference given by you the biochemical recation products and substrates , thus thereis need for more attention to fundamental carbohydrate chemistry , try to do calaculations with dimentional analysis to validadte your hyothesis NREL reorts can be correct , but the substrate is not hexoses , as mol balance for xylose are not same as hexose for calaculation of yireld

Theoretical yield for hexoses and pentoses = 51.14%, as one mole hexose when fermented gives two moles ethanol while three moles pentose give five moles ethanol, as mentioned by McMillan (1993) and Krishnan et al., (1999).

Krishnan M.S., N.W. Ho and G.T. Tsao, 1999. Fermentation kinetics of ethanol production from glucose and xylose by recombinant Saccharomyces 1400 (pLNH33). Appl. Biochem. Biotech., 77(79): 373-388.

McMilan J. D., 1993. Xylose fermentation to ethanol: A review. National Renewable Energy Labortory, Midwest Research Institute, operated for U.S. department of Energy, contract no. DE-AC02-83CH10093.