Two-Stage Fermentation of Lipomyces starkeyi for Production of Microbial Lipids and Biodiesel

Abstract

The high operating cost is currently a limitation to industrialize microbial lipids production by the yeast Lipomyces starkeyi. To explore economic fermentation technology, the two-stage fermentation of Lipomyces starkeyi using yeast extract peptone dextrose (YPD) medium, orange peel (OP) hydrolysate medium, and their mixed medium were investigated for seven days by monitoring OD600 values, pH values, cell growth status, C/N ratios, total carbon concentration, total nitrogen concentration, residual sugar concentration, lipid content, lipid titer, and fatty acids profiles of lipids. The results showed that two-stage fermentation with YPD and 50% YPD + 50% OP medium contributed to lipid accumulation, leading to larger internal lipid droplets in the yeast cells. However, the cells in pure OP hydrolysate grew abnormally, showing skinny and angular shapes. Compared to the one-stage fermentation, the two-stage fermentation enhanced lipid contents by 18.5%, 27.1%, and 21.4% in the flasks with YPD medium, OP medium, and 50%YPD + 50%OP medium, and enhanced the lipid titer by 77.8%, 13.6%, and 63.0%, respectively. The microbial lipids obtained from both one-stage and two-stage fermentation showed no significant difference in fatty acid compositions, which were mainly dominated by palmitic acid (33.36–38.43%) and oleic acid (46.6–48.12%). Hence, a mixture of commercial medium and lignocellulosic biomass hydrolysate could be a promising option to balance the operating cost and lipid production.

Recent Advances in using Lipomyces starkeyi for the Production of Single-Cell Oil

“…65 In another study, the fermentation media composed of 50% YPD + 50% Orange peel exhibited larger internal droplets in the yeast cells and two-stage operations increased the lipid yield by 18.5-27.1%. 66 The co-fermentation of glucose and xylose using L. starkeyi AS 2.1560 in a two-stage fermenter under unsterile conditions was studied by Liu. 67 The fed-batch operation in the second stage with co-utilization of non-sterile lignocellulose-derived sugars accumulated high lipid (63.8%) after 46h of incubation.…”

“…Presently, the high operating expense is a challenge in the industrialization of single-cell oil production by L. starkeyi. 66 For an economically advantageous process, the lipid yield and productivity need to be further enhanced. A metabolic engineering approach that targets potential genes can be an approach to enhance lipid production.…”

Exploring Yeast Diversity to Produce Lipid-Based Biofuels from Agro-Forestry and Industrial Organic Residues

“…As a strategy to achieve high lipid concentrations without compromising biomass production, two-stage batch processes were used in which cell proliferation occurs first, in a rich medium, and lipid accumulation occurs later, under nitrogen-limiting conditions [ 19 , 60 ]. Under such conditions, lipid production by L. starkeyi NRRL Y-1388 increased by 78% [ 192 ]. When L. tetrasporus Y-11562, L. kononenkoae Y-7042 and R. toruloides Y-1091 were used and a C/N 60 was present in the first phase and a C/N ~500 in the second phase, lipid productivity was three to seven times higher than was possible during the first growth phase [ 60 ].…”

Simple and Economical Downstream Process Development for Edible Oil Production from Oleaginous Yeast Lipomyces starkeyi

“…Oleaginous yeasts are advantageous producers that can accumulate oil, whose major component is triacylglycerides (TAG), up to approximately 60% of their dry cell mass [5,6]. The oils produced by Lipomyces starkeyi (hereafter referred to as yeast oil) are similar in fatty acid composition (rich in palmitic acid and oleic acid) and physical properties (solid at room temperature) to palm oil; therefore, it is expected to be an alternative palm oil from the viewpoint of flexible manufacturing locations and sustainability because there will be no need to harvest forests [7][8][9][10]. In addition, Lipomyces starkeyi has great industrial potential as an excellent lipid producer because it is a suitable host for genetic engineering to improve lipid production [11].…”