Abstract
The coproduction of lipid and carotenoid by red yeasts in one cycle is more convenient and economical for the industrial sectors, while the kinetics correlation between both products under different culture conditions has been scarcely studied. This study is aiming to correlate the impact of different carbon sources, carbon to phosphorus ratio (C/P), temperature, aeration, pH, and metals on dry cell weight, lipid (GC and fluorescence microscope), and carotenoid (HPLC) production by Rhodotorula glutinis, and applying a novel feeding approach using a 5 L bioreactor to enhance carotenoid and unsaturated fatty acid production by R. glutinis. Whatever the culture condition is, the reversible correlation between lipid and carotenoid production was detected. Remarkably, when adding 0.1 mM BaCl2, cellular lipid was significantly increased 14% more than the control, with 79.3% unsaturated fatty acid (46% C18:2 and C18:3) and 50% γ-carotene, while adding 1 mM NiSO4, cellular carotenoid was enhanced around 53% than the control (torulene 88%) with 81% unsaturated fatty acid (61% oleic acid). Excitingly, 68.8 g/l biomass with 41% cellular lipid (79% unsaturated fatty acid) and 426 µgpigment/gdcw cellular carotenoid (29.3 mg/L) (71% torulene) were obtained, when the pH-temperature dual controlled process combined with metallo-sulfo-phospho-glucose feeding approach in the 5 L bioreactor during the accumulation phase was conducted. This is the first study on the kinetic correlation between lipid and carotenoid under different C/P ratio and the dual effect of different metals like NiSO4 on lipid and carotenoid production by red oleaginous yeasts, which in turn significant for enhancing the coproduction of lipid and carotenoid by R. glutinis.
Highlights
Red oleaginous yeasts are a broad group of yeasts, which are characterized by producing many valuable metabolites such as lipids and carotenoid [1], one of the main representative genus of those colored yeasts is Rhodotorula glutinis
Different culture conditions were investigated to correlate the production of lipid and carotenoid production by R. glutinis, as well as investigating the possibilities to improve the lipid and carotenoid profile of R. glutinis through culture conditions manipulation
The results revealed that all the studied conditions showed a reversible relationship between lipid and carotenoid production under the studied culture conditions
Summary
Red oleaginous yeasts are a broad group of yeasts, which are characterized by producing many valuable metabolites such as lipids and carotenoid [1], one of the main representative genus of those colored yeasts is Rhodotorula glutinis. R. glutinis can accumulate lipid up to 60% of its dry cell [2] This yeast primarily synthesizes palmitic acid (C16:0), oleic acid (C18:1), linoleic acid (C18:2), and α-linolenic acid (C18:3) [1]. Based on a nutritional classification, fatty acids that are not synthesized by humans and are indispensable for development and health are known as essential, while those produced by humans are classified as non-essential fatty acids [3]. In this context, linoleic and alpha-linolenic acids are Processes 2020, 8, 140; doi:10.3390/pr8020140 www.mdpi.com/journal/processes. Oleic acid was demonstrated to induce beneficial anti-inflammatory effects on autoimmune diseases [10], protective effects on breast cancer, and improvement of immune system function [11,12]
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