Abstract
Citric acid was produced with free and k-carrageenan-entrapped cells of the yeast Yarrowia lipolytica in single and repeated batch-shake-flask fermentations on glycerol-based media. Simultaneous solubilization of hydroxyapatite of animal bone origin (HABO) was tested in all experiments. The highest citric acid production by free yeast cells of 20.4 g/L and 18.7 g/L was reached after 96 h of fermentation in the absence and presence of 3 g/L HABO, respectively. The maximum values for the same parameter achieved by gel-entrapped cells in conditions of single batch and repeated-batch fermentation processes were 18.7 g/L and 28.1 g/L registered after 96 h and the 3d batch cycle, respectively. The highest citric acid productivity of 0.58 g L−1 h−1 was obtained with immobilized cells in repeated batch mode of fermentation when the added hydroxyapatite of 3 g/L was solubilized to 399 mg/L whereas the maximum efficiency of 89.0% was obtained with 1 g/L of HABO.
Highlights
The yeast Yarrowia lipolytica is one of the more intensively studied nonconventional yeast species and much progress has been made in areas related to its environmental and industrial applications in the past few years [1]
The range of substrates used by Y. lipolytica include alkanes, fatty acids, organic acids, proteins, and some sugars, which contribute for the interest in this yeast
The yeast Yarrowia lipolytica was widely experimented in studies on soil-plant systems due to its well-pronounced phosphate solubilizing activity [4], plant beneficial interactions with arbuscular mycorrhizal fungi and nitrogen-fixing bacteria [5, 6], and as a key element in soil restoration schemes [7]
Summary
The yeast Yarrowia lipolytica is one of the more intensively studied nonconventional yeast species and much progress has been made in areas related to its environmental and industrial applications in the past few years [1]. Enzymes (proteases, lipases, esterases, and phosphatases), single-cell protein, and single-cell oil are the major products obtained from Y. lipolytica. The range of substrates used by Y. lipolytica include alkanes, fatty acids, organic acids, proteins, and some sugars, which contribute for the interest in this yeast. The yeast Yarrowia lipolytica was widely experimented in studies on soil-plant systems due to its well-pronounced phosphate solubilizing activity [4], plant beneficial interactions with arbuscular mycorrhizal fungi and nitrogen-fixing bacteria [5, 6], and as a key element in soil restoration schemes [7]
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