Regulation of biosynthesis of lipids in Chlorella vulgaris by compounds of zinc, chromium and selenium

Abstract

We studied molecular and metabolic mechanisms of regulated lipid biosynthesis in Chlorella vulgaris aquaculture. after addition of sodium selenite (10 mg/dm3) when added separately and in combination with Zn2+ (5 mg/dm3) and Cr3+ (5 mg/dm3) during 7 days of their action in order to obtain biotechnologically useful lipid products, enriched with microelements. Experiments were carried out in accordance with generally accepted hydrological and biochemical methods. It was established that micronutrients that were added into the medium result in an increase in the total content of lipids in the range of 10%. The redeployment of lipid classes in chlorella cells occurs due to the action of sodium selenite in favour of phospholipids by reducing the proportion of diacylglycerols, while the amount of triacylglycerols and nonetherified fatty acids does not change. Combined action of sodium selenite and zinc ions leads to the significant increase of the relative content of diacylglycerols, and partial increase of nonetherified fatty acids, at the same time in the cells we can observe a slight decrease in the proportion of triacylglycerols and phospholipids. Inclusion of 14C-bicarbonate in carbohydrates, proteins and lipids of Ch. vulgaris is significantly different both from the control group and from the group to which we added the investigated factors. However, the predominance of inclusion in lipids is 2–3 times higher than its inclusion into carbohydrates and 9–12 times higher in proteins. The increase of labeled bicarbonate inclusion intensity into carbohydrates occurs only in the case of joint action of sodium selenite and zinc ions, in proteins and lipids – in all cases of trace elemental activity. It was revealed that the general tendency is the reduction of the inclusion of bicarbonate in Ch. vulgaris triacylglycerols and its increase in phospholipids and nonetherified fatty acids, except for chromium ions, that modified the inclusion of the label into diacylglycerols, which may be due to the specific toxicity of the metal ions. The activation of lipogenesis after addition of selenium, zinc and chromium compounds was confirmed by an increase in the inclusion intensity of 14C-oleate in various classes of lipids that are present in chlorella and increased activity of glycerol-3-phosphatacyltransferase. Direction and regulation of lipid metabolism in Ch. vulgaris in the direction of increasing the amount and accumulation of lipids and their separate classes using sodium selenite in combination with Zn2+ and Cr3+ with the purpose of forming selenium-metal-lipid complexes can be used to obtain biologically active lipidous preparations enriched with essential microelements.