Influence of a Film Yeast, Candida Krusei, on the Heat Resistance of Certain Lactic Acid Bacteria Grown in Symbiosis with it

Abstract

A comparison of the heat resistance of certain lactic acid bacteria grown in pure culture and in symbiosis with a filmforming yeast, Candida krusei, revealed that the bacteria nearest the yeast pellicle were more active after a severe heat treatment than were those farthest from the surface growth (Peppler and Frazier, 1941). No report on this result of symbiosis has been found in the literature. It was believed that better use might be made of this relationship in the preparation of cultures of thermoduric bacteria if more were known concerning the causes of the beneficial effect of Candida krusei. The influence of accessory growth substances, reduced acidity, reduced oxygen tension, and combinations of these factors was considered. Growth with acid-destroying yeasts is known to prolong markedly the viability of common dairy streptococci and lactobacilli (Northrup, 1912; Hastings and Catley, 1927; Slobodska-Zaykowska, 1926). The association of certain lactobacilli with film-forming yeasts is reported to increase their rate of acid production (Hastings and Catley, 1927; Lott, 1926; Severine and Paraschuk, cited by Palladina and Masjukewitsch, 1931). A new aspect of symbiosis, the stimulation of lipolysis by Mycotorula lipolytica during growth with lactic acid bacteria, was reported by Fouts (1940).

Factors Affecting the Heat Resistance of Nonsporing Organisms

“…Other conditions of growth may have an influence on heat resistance. It has been found (Peppler & Frazier, 1941) that successive transfers every 12-24 h resulted in more active cultures of L. helveticus a t 40" than at 37" when the mother cultures were grown in skimmilk. But this difference was reduced when neopeptone or malt extract was added to the mother culture.…”