A comparative study on glycerol metabolism to erythritol and citric acid inYarrowia lipolyticayeast cells

Abstract

Citric acid and erythritol biosynthesis from pure and crude glycerol by three acetate-negative mutants of Yarrowia lipolytica yeast was investigated in batch cultures in a wide pH range (3.0-6.5). Citric acid biosynthesis was the most effective at pH 5.0-5.5 in the case of Wratislavia 1.31 and Wratislavia AWG7. With a decreasing pH value, the direction of biosynthesis changed into erythritol synthesis accompanied by low production of citric acid. Pathways of glycerol conversion into erythritol and citric acid were investigated in Wratislavia K1 cells. Enzymatic activity was compared in cultures run at pH 3.0 and 4.5, that is, under conditions promoting the production of erythritol and citric acid, respectively. The effect of pH value (3.0 and 4.5) and NaCl presence on the extracellular production and intracellular accumulation of citric acid and erythritol was compared as well. Low pH and NaCl resulted in diminished activity of glycerol kinase, whereas such conditions stimulated the activity of glycerol-3-phosphate dehydrogenase. The presence of NaCl strongly influenced enzymes activity - the effective erythritol production was correlated with a high activity of transketolase and erythrose reductase. Therefore, presented results confirmed that transketolase and erythrose reductase are involved in the overproduction of erythritol in the cells of Y. lipolytica yeast.

Metabolic Flexibility of Yarrowia lipolytica Growing on Glycerol

“…Instead they reach titers of up to 29.7 g * L −1 and 12.5 g * L −1 for mannitol and erythritol respectively (see strain HA 834, Table S2) with a total conversion yield for polyols of up to 0.47 g * g −1 from pure glycerol at low pH. As we could show for Y. lipolytica DSM 3286, the adjustment of process conditions (pH), as well as the salt concentration in the media (demonstraded by Tomaszewska et al, 2014a), can shift the metabolite pattern toward a certain direction (e.g., from mannitol to erythritol formation). According to Fleet (1990) some of the common properties of yeast species isolated from dairy products is their ability to assimilate citric acid and withstand low pH conditions.…”

“…Both methods often lead to a fluctuating pH environment during the cultivation and consequently often to diverging results. Moreover, the addition of salts can have a decisive impact on strain performance (Tomaszewska et al, 2014a). Therefore, we decided to use unbuffered YNB medium in shake flask experiments, which lead to a decrease in pH from 5.5 to values around 2.0.…”

“…Studies have shown the dependence of the metabolism on the environment. Especially, varying pH conditions have a major impact on the product spectrum formed during bioconversion processes with this yeast (Tomaszewska et al, 2012, 2014a). Growth of many yeast species is limited to a certain pH optimum, with decreasing growth rates when the pH is not optimal.…”

Engineering Yarrowia lipolytica for Enhanced Production of Lipid and Citric Acid

“…The metabolism of glycerol to citric acid [42] and lipogenesis pathway [43] in Y. lipolytica has been studied before. Glycerol is assimilated into the cell via facilitated diffusion and is subsequently phosphorylated [41].…”

Physiologo-biochemical characteristics of citrate-producing yeast Yarrowia lipolytica grown on glycerol-containing waste of biodiesel industry

“…The values are the means of the three experiments and two measurements for each experiment which varied by no more than 10 % The values are the means of the three experiments and two measurements for each experiment, which varied by no more than 10 % I, the exponential growth phase; II, the retardation phase, the start of acid synthesis; III, the stationary phase, active acid production metabolism by means of its phosphorylation by glycerol kinase (Ermakova and Morgunov 1987;Makri et al 2010;Workman et al 2013;Tomaszewska et al 2014), while fatty acids are metabolized via the glyoxylate cycle (Ermakova et al 1986;Holdsworth et al 1988;Kamzolova et al 2011b). It should be noted that in glycerol-grown cells, the glyoxylate cycle is inactive (Morgunov et al 2004a;Kamzolova et al 2011b), as in microbial cells grown on glucose (Rohr and Kubicek 1981;Ermakova et al 1986;Holdsworth et al 1988).…”