The citric acid production from raw glycerol by Yarrowia lipolytica yeast and its regulation

Abstract

The optimal cultivation conditions ensuring the maximal rate of citric acid (CA) biosynthesis by glycerol-grown mutant Yarrowia lipolytica NG40/UV7 were found to be as follows: growth limitation by inorganic nutrients (nitrogen, phosphorus, or sulfur), 28 °C, pH 5.0, dissolved oxygen concentration (pO₂) of 50 % (of air saturation), and pulsed addition of glycerol from 20 to 80 g L⁻¹ depending on the rate of medium titration. Under optimal conditions of fed-batch cultivation, in the medium with pure glycerol, strain Y. lipolytica NG40/UV7 produced 115 g L⁻¹ of CA with the mass yield coefficient of 0.64 g g⁻¹ and isocitric acid (ICA) amounted to 4.6 g L⁻¹; in the medium with raw glycerol, CA production was 112 g L⁻¹ with the mass yield coefficient of 0.90 g g⁻¹ and ICA amounted to 5.3 g L⁻¹. Based on the activities of enzymes involved in the initial stages of raw glycerol assimilation, the tricarboxylic acid cycle and the glyoxylate cycle, the mechanism of increased CA yield from glycerol-containing substrates in Y. lipolytica yeast was explained.

Engineering Yarrowia lipolytica for Enhanced Production of Lipid and Citric Acid

“…They reported a citric acid production range of 71 to 98 g/L by Y. lipolytica strains when they were fed with pure or impure glycerol under the nitrogen-limiting conditions [34]. The citric acid production can be further enhanced by adjusting the pH and dissolved oxygen [16]. However, it should be noted that the control over oxygen did not significantly affect citric acid production from Y. lipolytica grown on glycerol, as sole source of carbon [64].…”

Production of valuable compounds by molds and yeasts

“…Other uses include chemicals (surfactants and synthetic detergents), medicinals, textiles and metallurgy. 120 Fumaric acid, a 4-carbon dicarboxylic acid, is made by species of Rhizopus at levels of 126-130 g l − 1 . 121 Rhizopus arrhizus has been utilized by the Pfizer corporation to make 4000 tons per year.…”

Utilization of biodiesel-derived glycerol or xylose for increased growth and lipid production by indigenous microalgae

“…The availability of crude (or technical) glycerol as a cheap carbon source has led to many studies evaluating the use of crude glycerol as feedstock for the biological production of valuable chemicals as dihydroxyacetone, citric acid, vancomicin, cephalosporine and others (Dobson et al 2012;Liu et al 2013;Morgunov et al 2013;Shin et al 2011;Zeng et al 2013). However, if these conversion processes are successful, the value of their products, produced at enormous levels, would also fall precipitously.…”