Ganoderic Acid Production Research Articles

Submerged cultivation of medicinal mushrooms for production of valuable bioactive metabolites.

Mushrooms are abundant sources of a wide range of useful natural products. Nowadays, commercial mushroom products are from mushrooms collected from field cultivation, which is a time-consuming and labor-intensive process. Submerged cultivation of mushrooms has significant industrial potential, but its success on a commercial scale depends on cost compared with existing technology. Increasing product yields and development of novel production systems that address the problems associated with this new technology will certainly facilitate expansion. This article outlines the major valuable metabolites produced by mushroom cultivation and advances in submerged culture of mushrooms, taking Ganoderma lucidum, a popular folk and an oriental medicine used to treat many diseases, as a typical example. Our latest data on mushroom cultivation for efficient production of bioactive ganoderic acids and Ganoderma polysaccharides in bioreactors are presented.

Role of oxygen supply in submerged fermentation of Ganoderma lucidum for production of Ganoderma polysaccharide and ganoderic acid

The effects of oxygen supply on the submerged fermentation of Ganoderma lucidum, a famous traditional Chinese medicinal mushroom, for simultaneous production of bioactive compounds— Ganoderma polysaccharide and ganoderic acid (GA) were studied. An initial volumetric oxygen transfer coefficient ( K La) value within the range of 16.4–96.0 h −1 had a significant effect on the cell growth, cellular morphology and metabolites biosynthesis. At an initial K La of 78.2 h −1, a maximal cell concentration of 15.62 g l −1 by dry weight was obtained, as well as a maximal intracellular polysaccharide (IPS) production of 2.19 g l −1 and its maximal productivity of 217 mg l −1 per day. An increase of initial K La led to a bigger size of mycelia aggregates and a higher production and productivity of GA. The GA production and productivity at an initial K La of 96.0 h −1 was 1.8-fold those at an initial K La of 16.4 h −1. Dissolved oxygen tension (DOT) also affected the fermentation process. The cell growth of G. lucidum was significantly inhibited when DOT was controlled ∼10% of air saturation, which was due to the oxygen limitation in mycelia aggregates. The production of extracellular polysaccharide (EPS) and contents of IPS and GA ∼10% of DOT were higher than those ∼25% of DOT. However, the total production and productivity of IPS and GA at a low DOT were lower than those at a high DOT. The fundamental information obtained in this study will be useful for submerged fermentation of G. lucidum on a large scale.

Significance of inoculation density control in production of polysaccharide and ganoderic acid by submerged culture of Ganoderma lucidum

Control of inoculation density was significant for cell growth, morphology, and production of polysaccharide and ganoderic acid in submerged culture of the higher fungus Ganoderma lucidum. A maximal cell concentration of 15.7 g dry cell weight (DW)/l was obtained at an inoculation density of 330 mg DW/l. For inoculation density within the range of 70–670 mg DW/l, a large inoculation density led to a small pellet size and high production of extracellular and intracellular polysaccharides, while a relatively big pellet size and high accumulation of ganoderic acid were observed at a low inoculation density. It was also shown that small pellet size resulted in high polysaccharide production, while large pellet size led to high production of ganoderic acid.

Fed-batch fermentation of Ganoderma lucidum for hyperproduction of polysaccharide and ganoderic acid

A process for simultaneous efficient production of bioactive ganoderic acid (GA) and Ganoderma polysaccharide by fed-batch fermentation of Ganoderma lucidum was developed. Effects of carbon source and initial sugar concentration on the production of GA and polysaccharide were studied at first. Sucrose as a carbon source was suitable for the extracellular polysaccharide (EPS) production although the cells could not grow well. Lactose was beneficial for the cell growth and production of GA and intracellular polysaccharide (IPS). When the initial lactose concentration exceeded 35 g/l, the GA accumulation was decreased. The GA production was remarkably improved by pulse feeding of lactose, when its residual concentration was between 10 and 5 g/l. The fed-batch fermentation process in shake flasks could be successfully reproduced in stirred bioreactors (STR) with dissolved oxygen (DO) controlled between 20 and 35% of air saturation during fermentation. The maximum cell density reached 21.89±0.35 and 20.95±0.01 g DW/l in STR and flasks, respectively. The production of EPS reached 0.87±0.05 (STR) and 0.75±0.05 g/l (flask), and the total production of IPS reached 2.49±0.07 (STR) and 2.40±0.05 g/l (flask). The total production of GA reached 367.1±17.4 and 297.9±13.7 mg/l for STR and flask, respectively, and their corresponding productivity was 29.6±0.5 and 14.3±0.1 mg/l per day. Not only the cell density but also the content, production and productivity of GA and IPS obtained in this work are the highest reported in agitated fermentation of G. lucidum.

Submerged fermentation of higher fungus Ganoderma lucidum for production of valuable bioactive metabolites—ganoderic acid and polysaccharide

The effects of nitrogen source and initial glucose concentration were studied in submerged fermentation of higher fungus Ganoderma lucidum for simultaneous production of bioactive ganoderic acid and polysaccharide. The cells could not grow well when either yeast extract or peptone was used as the sole nitrogen source. However, a combined addition of 5 g/l of yeast extract and 5 g/l of peptone was optimal for the cell growth and metabolite production. Initial glucose concentration within 20–65 g/l also greatly affected the cell growth and product biosynthesis. The extracellular polysaccharide production was remarkably improved at a high initial glucose concentration. The highest levels of cell density (16.7 g DW/l), intracellular polysaccharide (1.19 g/l) and ganoderic acid (212.3 mg/l) were obtained at an initial glucose concentration of 50 g/l.

Two-stage culture process for improved production of ganoderic acid by liquid fermentation of higher fungus Ganoderma lucidum.

Investigations on the impact of pellet size on the cellular oxygen uptake and accumulation of ganoderic acid (GA) suggested the favorable effect of oxygen limitation on GA formation by the higher fungus Ganoderma lucidum. A two-stage fermentation process was thus proposed for enhanced GA production by combining conventional shake-flask fermentation with static culture. A high cell density of 20.9 g of DW/L (DW = dry cell weight) was achieved through a 4-day shake-flask fermentation followed by a 12-day static culture. A change in the cell morphology and a decrease in the sugar consumption rate were observed during the static culture. The GA production in the new two-stage process was considerably enhanced with its content increased from 1.36 (control) to 3.19 mg/100 mg of DW, which was much higher than previously observed.

Effect of initial pH on production of ganoderic acid and polysaccharide by submerged fermentation of Ganoderma lucidum

The effects of initial pH on simultaneous production of ganoderic acid and a polysaccharide by the fungus Ganoderma lucidum were investigated in shake flasks. An initial pH value, varying within the range of 3.5–7.0, had a significant effect on the cell growth and product biosynthesis. At an initial pH of 6.5, a maximum in biomass of 17.3±0.12 g/l by dry weight (DW) was obtained, as well as a maximal specific production of ganoderic acid of 1.20±0.03 mg/100 mg DW and total production of 207.9±2.7 mg/l. Lowering the initial pH from 6.5 to 3.5 gradually led to a higher production of extracellular polysaccharide and a higher specific production of intracellular polysaccharide.