Influence of Glucose and Saturated Free-Fatty Acid Mixtures on Citric Acid and Lipid Production by Yarrowia lipolytica

Abstract

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.

Lipids of oleaginous yeasts. Part II: Technology and potential applications

“…Therefore, the specific growth rate of lipid-free material (m Xf ) was illustrated by the following formula: m Xf ¼ m Xfmax N=ðK N þ NÞ ð Þ , where K N was the saturation constant for nitrogen (in g/L) [60]. In this assumption is considered that lipid-free material is the ''active'' biomass portion [60,[88][89][90].…”

“…Nevertheless, in similar types of processes (e.g., production of citric acid from glucose or glycerol), the specific production rate of citric acid was considered to be a constant (q Cit ¼ a) [90,92,93].…”

“…philic substrates (glucose and/or glycerol) with various fatty materials has been employed [40,90,113,[116][117][118][119][120], whereas with some exceptions in which batch bioreactor experiments were performed [94,105,106,108,113,116], in most trials shake-flask trials have been carried out.…”

Yarrowia lipolytica as an Oleaginous Cell Factory Platform for Production of Fatty Acid-Based Biofuel and Bioproducts

“…At concentrations of 320 g/L, glucose can reduce growth in engineered strains (Blazeck et al, 2014). At lower concentrations of 150 g/L, growth remains unchanged under nitrogen-limited conditions, but unsaturated FAs content is depleted (Papanikolaou et al, 2006). In a recent study, Y. lipolytica showed a decrease in growth with higher glycerol concentration, from 50 to 300 g/L in a chemically defined medium (Sriwongchai et al, 2013).…”

“…However, it poses a challenge to rely solely on selecting versatile strains and modifying environmental conditions in order to accomplish this. For instance, the level of lipid accumulation rarely rises above 20% of the dry weight in Y. lipolytica when glucose is the sole source of carbon (Papanikolaou et al, 2006). This leaves some spaces for metabolic engineering.…”