Micro-Organisms and Fermentation (Paperback)

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: as to keep continually in a state of absolute purity. It is, however, one of the most salient features in the present development of the industry of fermentation, that efforts based upon the right understanding of the paramount importance of the fermentation organisms are being made to emancipate the chief useful species from the action of injurious forms. The very great importance of this was not, however, appreciated until Hansen, through methodical selection of certain types of yeast, showed that such a pure growth insures far greater certainty and uniformity than the impure and unknown yeast mixtures hitherto used. We shall come back to this point later on (Chapter VI.). In experiments in the laboratory, where the object is likewise to prepare cultures of fermentation organisms, greater demands may naturally be made than on a practical scale. In this case it is necessary to work with absolutely pure cultures, partly in small quantities, partly in masses so large that they may be transferred at a given point of time from the laboratory to the brewery. Conditions which are wanting in practice are sought to be realised in the laboratory, which is specially arranged for such investigations. We will now briefly mention these requirements and the way in which they are met, and, for purely historical reasons, we will begin with the last link, viz., with the vessels and liquids which receive the originally-prepared small pure cultures, and the expedients to be employed in their cultivation. It is necessary that these vessels and liquids be sterile before the inoculating substance is introduced, i.e.., they must be freed from all living germs; also that the various utensils and the air in the place where the work is performed should contain as few living germs as possible. The same...