This is a really great project, and your question is a good one. If you are hydrolyzing the lignocellulosic biomass with sulfuric acid and neutralizing with NaOH, the high concentration of sodium sulfate will inhibit the growth of the yeast. However, the removal of the ions is a challenging. Here are some possible methods for this step.
The sugars that you want to keep are neutral and the sodium and sulfate are ionic, so it is possible to use an ion exchange resin to remove the ions. A mixed bed resin containing a equal mixture of anion and cation exchange capacity would remove both the sodium and the sulfate. The procedure is easy; you just add the resin to the sample and stir for an hour. The problem with this method, is that it is difficult to regenerate the resin, so it would be an expensive method. http://en.wikipedia.org/wiki/Ion-exchange_resinhttp://www.sigmaaldrich.com/catalog/pro ... ®ion=US
An ion retardation resin would allow separation of the sugars from the salt. You pack this resin in a column, and apply the sample. The glucose elutes from the column first and the ions are retarded and elute later. You can reuse this resin many times by washing the ions through with water. The problem is that you need a chromatography column to pack the resin in.http://www.google.com/#hl=en&sugexp=les ... 80&bih=585
Another possibility is to use barium hydroxide to neutralize the sample. Barium precipitates with sulfate and the hydroxide and hydrogen ions would combine to give a neutral solution. If you were careful to add an equal molar concentration of barium hydroxide to neutralize the sulfuric acid, this would yield a sample with a very low salt concentration. The problem with this method is that barium hydroxide is toxic, so you might need to get prior approval to work with this reagent.http://www.sciencebuddies.org/science-f ... chem.shtml
Here is a source for barium hydroxide:http://www.carolina.com/catalog/search- ... SearchForm
Here is a college lab experiment on biofuel production and includes lots of information on variables that affect yeast fermentation. Check out the references in this lab handout to get an idea of what quantity of yeast would be needed for each fermentation sample. The quantity and age of the yeast used to start the fermentation would be one of your controlled parameters. If you can't find more specific information, I would recommend starting with 100-1000 yeast cells per ml, so you can see the growth curve as the yeast grows. http://www.marietta.edu/~biol/introlab/bfuelrsc.pdf
What is the purpose of your experiment? Please let me know if you need any more detailed information.