| Abstract: | Summary 1. Cereal straw was partially hydrolyzed with dilute sulphuric or hydrochloric acid at elevated temperatures, yielding about 20% of matter assimilable byTorulopsis utilis (calculated on oven-dry straw), which consisted chiefly of xylose, with small amounts of glucose and acetic acid.2. Experiments on a laboratory scale with non-fermentable substrates like ethanol and acetic acid showed that also in these cases an ample aeration is an essential condition for a good yield.3. Acetic acid is harmful to the yeast, even in small concentrations, when the pH is lower than 5.0.4. Small quantities of glucose or acetic acid stimulate the conversion of xylose byTorulopsis utilis.5. With an adequate aeration and an initial pH of 5.5–6.0 (maintained at this level until the acetic acid has disappeared and then lowered to 4.0–4.5) satisfactory conversion rates and yields could be obtained on straw extracts as mentioned sub 1.6. The results of the laboratory experiments mentioned sub 5 could be reproduced in a semi-technical installation with a capacity of 200 l straw extract.7. Good results were obtained in this installation with aVogelbusch aeration device, while foaming could be adequately controlled by means of a rotating wire screen. |
