Influence of glucose and saturated free-fatty acid mixtures on citric acid and lipid production by Yarrowia lipolytica

In the present report, the effect of glucose and stearin (substrate composed by saturated free-fatty acids) on the production of biomass, reserve lipid, and citric acid by Yarrowia lipolytica ACA-DC 50109 was investigated in nitrogen-limited cultures. Numerical models that were used in order to quantify the kinetic behavior of the above Yarrowia lipolytica strain showed successful simulation, while the optimized parameter values were similar to those experimentally measured and the predictive ability of the models was satisfactory. In nitrogen-limited cultures in which glucose was used as the sole substrate, satisfactory growth and no glucose inhibition occurred, although in some cases the initial concentration of glucose was significantly high (150 g/l). Citric acid production was observed in all trials, which was in some cases notable (final concentration 42.9 g/l, yield 0.56 g per g of sugar consumed). The concentration of unsaturated cellular fatty acids was slightly lower when the quantity of sugar in the medium was elevated. In the cases in which stearin and glucose were used as co-substrates, in spite of the fact that the quantity of cellular lipid inside the yeast cells varied remarkably (from 0.3 to 2.0 g/l - 4 to 20% wt/wt), de novo fatty acid biosynthesis was observed. This activity increased when the yeast cells assimilated higher sugar quantities. The citric acid produced was mainly derived from the catabolism of sugar. Nevertheless, citric acid yield on sugar consumed and citrate specific production rate, as evaluated by the numerical model, presented substantially higher values in the fermentation in which no fat was used as glucose co-substrate compared with the cultures with stearin used as co-substrate

Effect of Citrus essential oil addition upon growth and cellular lipids of Yarrowia lipolytica yeast

The chemical composition of the essential oil from fruits of the Greek citrus hybrid Citrus sinensis cv New Hall - Citrus aurantium was investigated by GC and GC-MS. Forty-four compounds were identified, representing 92.83% of the total oil. Limonene, myrcene, β-pinene, α-pinene and α-terpineol constituted the major components of the oil. The effect of the addition of this oil upon the behavior of Yarrowia lipolytica yeast was also investigated. The microorganism was aerobically grown on glucose and oil was added to the culture medium in various initial quantities (from 0.0 to 1.5 mL/L). The strain underwent significant inhibition exerted by the added essential oil; a decrease of the highest achieved biomass concentration, even if the oil was added to the culture medium at small concentrations (e.g. 0.3 mL/L), was observed. The more oil was added, the more the lag phase of the growth increased, while the biomass yield on glucose consumed decreased with the addition of the oil. When the essential oil was added to the medium, even at small concentrations, a significant increase of cellular medium-chain saturated fatty acids (12:0 and 14:0) resulting in an increase of saturated fatty acid content in the cellular lipids, was observed. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA

Biotechnological valorisation of raw glycerol discharged after bio-diesel (fatty acid methyl esters) manufacturing process: Production of 1,3-propanediol, citric acid and single cell oil

International audienceRaw glycerol, byproduct from bio-diesel production process, is used as carbon substrate in several biotechnological applications. Using Clostridium butyricum F2b, 47.1 g L−1 of 1,3-propanediol was produced in batch anaerobic cultures while substrate uptake rate (rS, expressed in g L−1 h−1) increased with increase in glycerol concentration in the medium. In continuous cultures, microbial behaviour was studied in transitory states after addition of 1,3-propanediol in the chemostat vessel. Microbial growth was not affected by the high 1,3-propanediol (which was added in the chemostat vessel) concentration, while butyric and acetic acids concentrations were increased. In a two-stage continuous culture, 43.5 g L−1 of 1,3-propanediol was produced with a total volumetric productivity of 1.33 g L−1 h−1. Yarrowia lipolytica ACA-DC 50109 was grown in nitrogen-limited aerobic cultures on raw glycerol and it exhibited remarkable biomass production even at high glycerol concentration media, while rS decreased with increase in glycerol concentration. Citric acid was produced after nitrogen depletion in the medium, with the highest quantity of 62.5 g L−1, and yield on glycerol consumed was 0.56 g g−1. Fatty acid analysis of total cellular lipids showed that glycerol concentration increase in the growth medium somehow increased the cellular unsaturated fatty acids content of lipids. Mortierella isabellina ATHUM 2935 exhibited satisfactory growth in nitrogen-limited aerobic cultures with raw glycerol used as sole substrate. When high initial glycerol quantities were employed (e.g. 100 g L−1), 4.4 g L−1 of lipid were accumulated corresponding to around 51% (wt/wt) of lipid in dry weight. rS constantly decreased with increase in glycerol concentration in the medium, and in all cases notable glycerol quantities remained unconsumed in the medium