Effects of low‐intensity ultrasound on the biomass and metabolite ofGanoderma lucidumin liquid fermentation

Abstract The use of ultrasound has the potential of improving the production of valuable substances in Ganoderma lucidum ( G. lucidum )—a well‐known fungus rich in bioactive compounds. The effect of different ultrasonic parameters on the fermentation of G. lucidum was studied. The results showed that under optimal ultrasonic conditions, the mycelium biomass and triterpenoids production increased by 26.99 and 33.62%, respectively ( p < .05). Compared with the control, ultrasonication notably increased ( p < .05) the content of intracellular and extracellular polysaccharides (by 18.48 and 35.90%) and flavonoids (by 30.27 and 12.00%) in mycelium. Ultrasonic treatment promoted growth, and increased metabolism of G. lucidum . Scanning electron microscopy images showed that ultrasonic treatment caused moderate breakages in mycelium leading to leaked content at recovery time of 0.5 hr. When the recovery time lasted for 3 hr, the mycelium was recovered with increased branches and tighter winding. The findings of Fluo‐4/AM suggested that the intracellular calcium ion concentration of the mycelium improved after ultrasound treatment, demonstrating the altering‐influence of sonication on the cell membrane permeability of mycelium. These results suggest that ultrasound is an efficacious approach to produce more biomass and metabolites of G. lucidum in liquid fermentation. Practical Applications Ultrasonic technology has been widely used in the field of food fermentation. By changing the ultrasonic time, power density or frequency or other conditions, the ultrasonic energy entering the cell suspension can be changed, thereby controlling the effect of ultrasound on microbial activity. The outcome of this work indicated that the use of ultrasonication in fermentation process of G. lucidum promoted its growth and metabolism. This study provides a theoretical basis for the application of ultrasonication technology in the microbial fermentation industry.