| Résumé | Isolation of Aerobacillus strains with desirable fermentative characteristics was facilitated by pasteurization of the original inoculum. Both cultural characteristics and fermentative capacity of the original isolates were extremely variable. Dissociation into more variant types occurred in later generations giving rise to further differences in fermentative characteristics.In the preparation of mashes particle size of wheat is unimportant in relation to yield provided the kernel has been broken. Since prolonged cooking is harmful, a standard procedure of sterilization for 1 hr. at 121 °C. has been adopted. Mashes containing over 15% wheat by weight are inefficiently fermented. Acid production in the mash may be controlled by the addition of excess calcium carbonate at the beginning of the fermentation, or by the addition of ammonia as required. The most satisfactory fermentation temperature is about 32.5 °C.The addition of yeast extract, malt extract, dried yeast, or corn steep liquor is essential for the preparation of an active inoculum. Fermentation of whole wheat mashes may also be enhanced by yeast extract. Removal of the gluten has little effect, but the bran, shorts, germ, and soluble nitrogenous constituents are necessary for a normal fermentation. Pure wheat starch with inorganic supplements can be only partially utilized.Under anaerobic conditions fermentation of a 15% mash is complete in 60 hr., but continuous removal of the carbon dioxide reduces this time to 48 hr. The diol–ethanol ratio for anaerobic fermentations is of the order of 1.3: 1.0. Aerobic conditions inhibit the fermentation, particularly ethanol formation, and 120 hr. are required for completion. The diol–ethanol ratio, however, may be raised to 3: 1 or higher. |
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