Since the publication of the first edition of this work in 1940, marked advances have been made in the subject by numerous investigators in many countries. The increase in interest in this field of microbiology which has thus been demonstrated and the wide range of the researches which have been carried on supply abundant proof of the recognition of the potential importance of fermentations and related processes in industrial biochemical operations. In this edition we have tried to keep pace with this gratifying extension of knowledge and to review it now in a form which may be useful to students of this branch of technology and to those concerned with research or technical application therein.

The inclusion of all this new material has made it desirable to revise and consolidate much of the earlier material and to present in the tables relating to production statistics, fermentation products, etc., the latest available data. The chapters on yeast have been rewritten into a single chapter and expanded by much new material on food and fodder yeasts, riboflavin production, and disunions of methods of operation industrially.

Five new chapters have been added, giving extended descriptions of new processes of saccharification, recent work on yeast production and , yeast products, the production and properties of 2,3-butanediol, the itaconic and related fermentations, and comprehensive discussion of antibiotics. All these have been prepared with special reference to industrial applications and the possibilities of future developments.