Effects of Oleic Acid Addition Methods on the Metabolic Flux Distribution of Ganoderic Acids R, S and T's Biosynthesis

Abstract

The effects of oleic acid addition methods on the metabolic flux distribution of ganoderic acids R, S and T's biosynthesis from Ganoderma lucidum were investigated. The results showed that adding filter-sterilized oleic acid in the process of submerged fermentation and static culture is of benefit to the synthesis of ganoderic acids R, S and T. The metabolic fluxes were increased by 97.48%, 78.42% and 43.39%, respectively. The content of ganoderic acids R, S and T were 3.11 times, 5.19 times and 1.44 times higher, respectively, than they were in the control group, which was without additional oleic acid. Ganoderic acids R, S and T's synthesis pathways (GAP), tricarboxylic acid cycles (TCA), pentose phosphate pathways (PP) and glycolysis pathways (EMP) were all enhanced in the process. Therefore, additional oleic acid can strengthen the overall metabolic flux distribution of G. lucidum in a submerged fermentation-static culture and it can reduce the accumulation of the by-product mycosterol. This study has laid an important foundation for improving the production of triterpenes in the submerged fermentation of G. lucidum.

Keywords: Ganoderma lucidum; ganoderic acid; metabolic flux analysis; oleic acid; submerged fermentation-static culture.

Figure 1

Substrate and product contents of G. lucidum submerged fermentation-static culture under different oleic acid addition methods.

Figure 1

Substrate and product contents of G. lucidum submerged fermentation-static culture under different oleic acid addition methods.

Figure 2

The metabolic network of ganoderic acids R, S and T synthesis by G. lucidum, submerged fermentation-static culture. AcAcCoA—acetoacetyl coenzyme A; AcCoA—Acetyl Coenzyme A; DMAPP—Dimethylallyl pyrophosphate; E4P—Erythrose-4-phosphate; ERG—Ergosterol; ERG (e)—Extracellular ergosterol; F6P—fructose-7-phosphate; FADH2—Reduced Flavin Dinucleotide; FPP—Farnesylpyrophosphate; G6P—Glucose-6-phosphate; GA3P—glyceraldehyde 3-phosphate; Ga R, S, T—Ganoderic acid R, Ganoderic acid S, Ganoderic acid T; GGPP—geranylgeranyl pyrophosphate; GLC—Glucose; GLC (e)—Extracellular glucose; GPP—Geranyl pyrophosphate; ICI—Isocitric acid; IPP—Isopentenyl pyrophosphate; LAN—Lanosterol; MY—Mycosterol; NADH—Nicotinamide adenine dinucleotide; OAA—Oxaloacetic acid; OS—2,3-Oxidosqualene; PYR—Pyruvate; PYR (e)—Extracellular pyruvate; R5P—Ribose-5-phosphate; Ru5P—ribulose 5-phosphate; SQ—Squalene; X5P—Xylulose phosphate; α-KG—α-ketoglutaric acid; α-KG (e)—Extracellular α-ketoglutaric acid.

Figure 3

Metabolic flux distribution of ganoderic acid R, synthesized by submerged fermentation-static culture under two methods of oleic acid addition. Left: Control (the 10th day of static culture); Middle: Filter-sterilized oleic acid (15th day of static culture); Right: High-temperature-sterilized oleic acid (10th day of static culture).

Figure 4

Metabolic flow distribution of ganoderic acid S, synthesized by submerged fermentation-static culture under two methods of oleic acid addition. Left: Control (the 10th day of static culture); Middle: Filtration-sterilization oleic acid (20 days of static culture); Right: High-temperature-sterilization oleic acid (10 days of static culture).

Figure 5

Metabolic flow distribution of ganoderic acid T, synthesized by submerged fermentation-static culture under two methods of oleic acid addition. Left: Control (the 20th day of static culture); Middle: Filtration-sterilization oleic acid (20 days of static culture); Right: High-temperature-sterilization oleic acid (10 days of static culture).