Spontaneous formation of a mannitol-producing variant of Leuconostoc pseudomesenteroides grown in the presence of fructose

Abstract

We report the spontaneous formation of a stable mannitol-producing variant of Leuconostoc pseudomesenteroides. The mannitol-producing variant showed mannitol dehydrogenase activity which was absent in the parental strain. It was also able to use fructose and glucose simultaneously, whereas the parental strain showed diauxic growth with these sugars. A possible explanation of these observations is discussed.

FIG. 1

Overview of the pathway of fructose utilization in mannitol-producing heterofermentative lactic acid bacteria. A more detailed pathway of hexose fermentation by heterofermentative lactic acid bacteria was presented by Axelsson (2). MDH, mannitol dehydrogenase.

FIG. 2

Growth, fructose utilization, and product formation of the wild-type L. pseudomesenteroides strain DSM 20193 (A, B) and the spontaneously formed mannitol-producing variant strain (C and D) in batch culture in fructose medium. (A and C) ●, growth (OD₆₀₀); ■, fructose; ▵, mannitol. (B and D) ○, lactate; ▴, acetate; □, ethanol. Each value represents the mean of duplicate measurements, which varied by not more than 5%. Carbon recovery varied between 95 and 105%.

FIG. 3

Growth, fructose utilization, and product formation of L. pseudomesenteroides strain DSM 20193 in continuous culture in fructose medium at 30°C, pH 4.5, and at a dilution rate of 0.1 h⁻¹ with 150 mM fructose. (A) ●, growth (OD₆₀₀); ■, fructose; ▵, mannitol. (B) ○, lactate; ▴, acetate; □, ethanol. Carbon recovery varied between 95 and 105%.