Background & Objective: Crude glycerol (Glol), used as substrate for screening eleven natural
Yarrowia lipolytica strains in shake-flask experiments. Aim of this study was to assess the ability
of the screened strains to produce biomass (dry cell weight; X), lipid (L), citric acid (Cit), mannitol
(Man), arabitol (Ara) and erythritol (Ery), compounds presenting pharmaceutical and biotechnological
interest, in glycerol-based nitrogen-limited media, in which initial glycerol concentration had been adjusted
to 40 g/L.
Methods: Citric acid may find use in biomedical engineering (i.e. drug delivery, tissue engineering, bioimaging,
orthopedics, medical device coating, wound dressings). Polyols are considered as compounds
with non-cariogenic and less calorigenic properties as also with low insulin-mediated response.
Microbial lipids containing polyunsaturated fatty acids (PUFA) are medically and dietetically important
(selective pharmaceutical and anticancer properties, aid fetal brain development, the sight function
of the eye, hormonal balance and the cardio-vascular system, prevent reasons leading to type-2 diabetes,
present healing and anti-inflammatory effects).
Results: All strains presented satisfactory microbial growth (Xmax=5.34-6.26 g/L) and almost complete
substrate uptake. The principal metabolic product was citric acid (Citmax=8.5-31.7 g/L). Production of
cellular lipid reached the values of 0.33-0.84 g/L. Polyols were also synthesized as strain dependent
compounds (Manmax=2.8-6.1 g/L, Aramax ~2.0 g/L, Erymax= 0.5-3.8 g/L). The selected Y. lipolytica
strain ACA-DC 5029 presented satisfactory growth along with synthesis of citric acid and polyols,
thus, was further grown on media presenting an increased concentration of Glol~75 g/L. Biomass, lipid
and citric acid production presented significant enhancement (Xmax=11.80 g/L, Lmax=1.26 g/L,
Citmax=30.8 g/L), but conversion yield of citric acid produced per glycerol consumed was decreased
compared to screening trials.
Conclusion: Erythritol secretion (Erymax=15.6 g/L) was highly favored, suggesting a shift of yeast metabolism
from citric acid accumulation towards erythritol production. Maximum endo-polysaccharides
(IPS) concentration was 4.04 g/L with yield in dry weight 34.2 % w/w. Y. lipolytica strain ACA-YC
5029 can be considered as a satisfactory candidate grown in high concentrations of crude glycerol to
produce added-value compounds that interest pharmaceutical and biotechnology industries.