Barley straw was examined as a substrate for yeast biomass or ethanol production,
Physical and chemical procedures were applied in order to convert the cellulosic
fraction of the straw into soluble sugars, mainly glucose, which in turn could be used
by a yeast strain as a carbon source, Pulverization and heat treatment (steaming
at 121°C for 1 hour) were carried out in addition to acid or alkali pretreatment uSing
either H2S0, or NaOH at different concentrations, In this regard, 4%H2S0, solution
was the most effective in hydrolyzing the straw which was indicated by the release of
the highest amount of soluble sugars, The supernatant resulted after acid
pretreatment was detoxified and neutralized usrnq overliming with different alkali,
Ca(OH)2, NaOH, 8a(OH)2, KOH Among the examined alkaline solutions; Ca(OH)~
was the best. The supernatant was not the suitable substrate in batch fermentation
for yeast biomass production USing Sacch. cerevisiae 2030, therefore, it was
examined for ethanol production USing Sacch. cerevisiae 0-14. The highest yield of
alcohol (75-78.3 % of the theoretical) did not greatly affected by the yeast (Sacch.
cerevisiee 0-14) inocula size; nevertheless, the fermentation period was shortened
when batches were inoculated with 10%. The solid cellulosic residues separated
after pretreatment were subjected to chemical hydrolysis using different
concentrations of NaOH or H2S04 and autoclaved at different temperatures (100, 121,
136°C) for 1 hour. The maximum amount of glucose was recorded with 2% H2S04
solution at 136°C for 1 hour. Production of yeast biomass from glucose, molasses and
acid hydrolyzate in 9-hour fed batch fermentations was investigated. The highest
Yield coefficient (210%) was obtained with glucose while the yield coefficient was
decreased to 105% and 80% when yeast was cultivated on molasses or ac.d
hydrolyzate, respectively.