Economical lipid production from crude glycerol using Rhodosporidiobolus fluvialis DMKU-RK253 in a two-stage cultivation under non-sterile conditions

Abstract

To enhance the microbial lipid production through Rhodosporidiobolus fluvialis DMKU-RK253, a two-stage cultivation process with a focus on cost reduction was developed. Low-cost raw materials, which are biodiesel-derived crude glycerol and monosodium glutamate were utilized to produce microbial lipids. A two-stage cultivation process was performed under non-sterile cultivation, and a response surface methodology was used to determine the effects of the interaction among factors in the first and second stages of cultivation while using shaking flask cultivation. In the first stage of cultivation, cells were cultivated in a nitrogen-rich medium for cell mass production. The optimal crude glycerol (30 g/L) and monosodium glutamate (5 g/L) concentrations, and the inoculum age (96 h), were found to improve cell mass production. In the second stage, a non-sterile crude glycerol solution was used to enhance lipid production without any aseptic techniques. An optimal crude glycerol concentration of 57 g/L with an initial pH of 7 and an initial cell concentration of optical density at 600 nm of 20 resulted in a high lipid production of 27.81 ± 1.86 g/L and maximum cell mass of 39.14 ± 0.08 g/L. These high lipid and cell mass concentrations consequent to achieve a high lipid content of 71.42% of the dry cell mass, a lipid yield of 0.34 g/g glycerol and a cell mass yield of 0.48 g/g glycerol. The low-cost raw materials were estimated to be US$0.80/kg for microbial lipid production. Therefore, a potential condition for the cultivation process of yeast that produces a high amount of inexpensive lipids has been demonstrated.