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Albany 2019: 20th Conversation - Abstracts

category image Albany 2019
Conversation 20
June 11-15 2019
Adenine Press (2019)

Nitrogen limitation triggers lipid synthesis of Torulaspora globose on various carbon substrates

It is well-known that the nature of the growth-limiting component has a significant effect on lipid synthesis in microorganisms with a typical diphase process. The limitation of yeast growth by mineral components of nutrition medium (for example, nitrogen) stimulates the intensive storage of lipids by the lipid-producer yeast, while with a carbon source deficiency, microorganisms synthesize a negligible amount of lipids (Dourou et al., 2018; Lazar et al., 2018).

The purpose of this work was to study the effect of the nature of the growth-limiting component on biomass composition and lipid synthesis of yeast Torulaspora globose VKPMY-953, cultivated on ethanol or glucose.

The selected strain T. globose VKPM Y-953 has a unique feature - the ability to intensively synthesize lipids in parallel with the growth of the culture, unlike the classical producers of lipids, in which intensive synthesis of lipids occurs after the completion of active growth.

As seen from Table, in the medium with ethanol as a carbon source under conditions of limitation of T. globose growth by nitrogen, a lipid synthesis was higher (43.8% of the biomass) than with an ethanol deficiency (17.8% of the biomass). Conversely, with ethanol deficiency, the biomass was characterized by a higher protein content (23.4% of biomass) and a biomass yield from the consumed substrate (YX/S) (54.4%) than with nitrogen limitation (16.7% of biomass and 31.1%, respectively); under these conditions, the lipid yield (YL/S) was higher by 27% than with a nitrogen deficiency. It is considered that lipids synthesized by microorganisms under deficiency of carbon substrate perform mainly a functional role in metabolism (take part in transport processes, regulate the activity of enzymatic systems, etc.). The purpose of growth-coupled lipid synthesis in T. globose is still unknown. It is possible that the studied strain is characterized by a higher proportion of functional lipids than other types of yeast.

The specific rates of lipid and protein synthesis were calculated per the unit of a lipid-free biomass fraction. The data presented in the Table show that the specific rate of lipid synthesis exceeded the specific rate of protein synthesis by 2 times with a nitrogen limitation and it was reduced by 1.7 times with an ethanol deficiency. Thus, the lipid accumulation in the cells of T. globose depends on the ratio between the rates of lipid and protein synthesis.

As seen from Table, the nature of the growth-limiting component had no significant effect on the fatty acid (FA) composition of lipids in T. globose. The predominant fatty acids included the unsaturated acids - oleic acid (C18:1) (41.5 - 51.5% of total FA), palmitoleic acid (C16:1) (26.2 - 29.2% of total FA) and palmitic acid (C16) (14.5 - 15.5% of total FA).

Lipogenesis of T. globose cultivated on glucose had the distinctive features: the lipid accumulation was reduced by 2.7 times in comparison with cells, grown on ethanol; the maximum amount of lipids (16% of the biomass) was synthesized with a nitrogen deficiency, while with a glucose deficiency, the biomass yield from the consumed substrate (YX/S) was maximum (21.8%); the fraction of oleic acid (C18:1) in the lipids was increased up to 63% (of the total amount of FA).

Thus, nitrogen limitation triggers lipid synthesis of T. globose on various carbon substrates.

The reported research was funded by RFBR (project № 18-38-00794_mol_а).

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References

    Lazar, Z., Liu, N., Stephanopoulos, G. (2018) Holistic Approaches in Lipid Production by Yarrowia lipolytica. Trends Biotechnol. 36(11), 1157-1170. doi: 10.1016/j.tibtech.2018.06.007

    Dourou, M., Aggeli, D., Papanikolaou, S., Aggelis, G. (2018) Critical steps in carbon metabolism affecting lipid accumulation and their regulation in oleaginous microorganisms. Appl. Microbiol. Biotechnol. 102(6), 2509-2523. doi: 10.1007/s00253-018-8813-z.

Nadezhda N. Stepanova
Svetlana V. Kamzolova
Igor G. Morgunov

Federal Research Center
Pushchino Center for Biological Research
Russian Academy of Sciences
G.K. Skryabin Institute of Biochemistry and Physiology of Microorganisms RAS
Pushchino
Moscow region 142290, Russia

Ph: (007) 9264145620
Fx: (007) 495-9563370
Email: nadinka_1994@mail.ru