Harnessing the Effect of pH on Lipid Production in Batch Cultures of Yarrowia lipolytica SKY7

Abstract

The objective of this research was to investigate the kinetics of lipid production by Yarrowia lipolytica SKY7 in the crude glycerol-supplemented media with and without the control of pH. Lipid and citric acid production were improved with the pH control condition. There was no significant difference observed in the biomass concentration with or without the pH control. In the pH-controlled experiments, the biomass and lipid concentration reached 18 and 7.78 g/L, (45.5% w/w), respectively, with lipid yield (Yp/s) of 0.179 g/g at 60 h of fermentation. The lipid production was directly correlated with growth and the process was defined as growth associated. After 60 h of fermentation, the lipid degradation was noticed in the pH-controlled reactor whereas it occurred after 84 h in the pH-uncontrolled reactor. Apart from lipid, citric acid was produced as the major extracellular product in both fermentations but the much lower concentration in uncontrolled pH. Based on the experimental results, it is evident that controlling the pH will enhance the lipid production by 15% compared to pH-uncontrolled fermentation.

Optimization of trace elements in purified glycerol for microbial lipid and citric acid production by Yarrowia lipolytica SKY7

“…Lipid characterization revealed that palmitic acid (C16:0), oleic acid (C18:1) and linoleic acid (C18:2) were produced in all glycerol media. Oleic acid (C18:1) and linoleic acid (C18:2) are the major components in the case of SKY7 as reported in other studies [11,12]. These lipids have a resemblance with the vegetable oil.…”

“…The reason for low lipid concentration and biomass lipid content in shake flask studies might also be due to uncontrolled pH in shake flask experiments. It has been reported that lipid and citric acid production improves under pH control (pH-6.5) condition for Y. lipolytica SKY7 Kuttiraja et al [11]. The residual glycerol profile for different trace elements has been highlighted in Fig.…”

“…The fermenters were operated under fedbatch mode to control substrate limitation. The production fermenters were operated at temperature 28 °C and pH 6.5 for Y. lipolytica SKY7 as reported by Kuttiraja et al [11]. No additional trace elements were added in fermenter 1 at 0 h. The fermenter 2 had only different sulfates at 0 h: Peptone was added at 0 h only to provide nitrogen for cell growth.…”

“…A constant supply of intracellular citrate will generate adequate amounts of acetyl-CoA in the cytoplasm by the enzyme ACL (ATP citrate lyase). Acetyl CoA is converted into malonyl-CoA (a step-in lipid synthesis) using ACC enzyme (acetyl-CoA carboxylase) [11]. If ACL enzyme gets inhibited, accumulated citrate in cytoplasm comes out of the cell instead of being converted into lipids.…”

Recombinant β-Carotene Production by Yarrowia lipolytica – Assessing the Potential of Micro-Scale Fermentation Analysis in Cell Factory Design and Bioreaction Optimization

“…Multiple strategies for enhancing lipid production and lipid accumulation in Yarrowia have been described in literature, such as depletion of nitrogen offsets lipid accumulation, which is achieved using a high carbon-to-nitrogen ratio (C/N ratio) ideally in a continuous cultivation (Gropoşila-Constantinescu et al, 2015;Kavšcek et al, 2015). It has also been described that lipid production in Yarrowia is favored at pH 5-6.5 (Beopoulos et al, 2008;Kuttiraja et al, 2017). Finally, the addition of the monounsaturated oleic acid as a cosubstrate has also been reported to promote lipid accumulation (Beopoulos et al, 2008).…”