276 FAMILY OF SACCHAROMYCETACEAE 



Genus XI 



Spherical or hemispherical ascospores, irregular or angulous in 

 form. Generally no fermentation is produced. Forms a strong my- 

 celium. 



PICHIA MEMBRANAEFACIENS. Hansen 

 Syn.: SACCHAROMYCES MEMBRANAEFACIENS. Hansen 



This species was found by Hansen in the gummy exudations of 

 the elm, by Koehler in well water and by Jorgensen in white wine. 

 It has been described by Hansen 1 and Siefert. 2 It resembles the 

 Mycodermae (Mycoderma cerevisiae, or vini). When cultivated on 

 beer wort a thick scum is rapidly formed, folded and grayish in color. 

 It is filled with air bubbles. The cells are spherical or elongated and 

 rich in vacuoles (Fig. 130). The temperature limits for budding in 

 beer wort are: minimum, 0.5 C. and maximum, 35 C.-36 C. The 

 scum is not formed at the temperature limits and the yeast vegetates, 

 then, as a deposit. 



The ascs form easily on plaster blocks and also in most of the 

 culture media and especially in the scums. They possess two spheri- 

 cal, elongated, hemispherical or oval ascospores, sometimes trian- 

 gular, which measure about 4.5 microns in length. According to 

 Nielsen, 3 the maximum temperature for budding is situated between 

 33 and 35 C., the minimum temperature between 2.5 and 2.7 C. and 

 the optimum between 30.5 and 31 C. At this latter temperature the 

 ascospores are formed in 19-21 hours. On wort gelatin, the colonies 

 develop on the surface of the substratum and look like a shield. 

 They are rugose and have a reddish tint. The gelatin is liquefied 

 very rapidly. The colonies which develop in the depths of the me- 

 dium have a different appearance and liquefy gelatin less rapidly. 

 This species does not invert saccharose, and according to Hansen, 

 does not ferment any sugar. However, Lindner has caused a slight 

 fermentation of dextrose and levulose. 



1 Hansen, E. C. Recherches sur la physiologic et la morphologie des fer- 

 ments alcooliques. VII, Action des ferments alcooliques sur les di verses especes 

 de sucre. Levures alcooliques a cellules ressemblant a des Saccharomyces. Comp. 

 Rend. du. lab. de Carlsberg, 2, Book 5, 1888; XI, La spore de Saccharomyces 

 devenue sporage. Recherches comparatives sur les conditions de croissance 

 vegetative et le developpement des organes de reproduction des levures et des 

 moisissures. Comp. Rend, du Lab. de Carlsberg, 5, Book 2, 1902. 



2 Siefert, W. Saccharomyces membranaefaciens. Ber. d. chem. Phys. Ver- 

 suchsst. Jlosternburg, 1899-1900. 



3 Nielsen, J. C. Sur le developpement des spores du Saccharomyces membranae- 

 faciens, du Sacch. Ludwigii, et du Sacch. anomalous. Comp. Rend, du lab. de 

 Carlsberg, 3, Book, 31, 1891. 



