Ganoderic Acid Production via Aerial Co-cultivation of Ganoderma lucidum with Bacillus subtilis and Aspergillus niger Using Bubble Column Bioreactor

Ganoderma lucidum, with its medicinal characteristics, is one of the most beneficial fungi in traditional Asian medicine. This fungus low efficiency of ganoderic acid production has limited its use as a valuable secondary metabolite. Environmental stresses and elicitors such as microbial volatile organic compounds in co-cultures can increase ganoderic acid production. To investigate effects of variables of co-culture time and volume on Ganoderma lucidum growth and ganoderic acid production, Bacillus subtilis and Aspergillus niger were aerially co-cultured with Ganoderma lucidum.

To investigate fungus growth and production of ganoderic acid using bubble column bioreactor, effects of independent variables of temperature, initial inoculation, length-to-diameter ratio (L: D) and aeration were investigated using Taguchi method. Then, effects of co-culture of Ganoderma lucidum with Bacillus subtilis and Aspergillus niger under optimum conditions were investigated.

Optimizing effects of co-culture time and volume variables led to 2.9-fold increases in production of ganoderic acid, compared to the control sample. Optimization of biomass production in the bioreactor showed that biomass production increased significantly by increasing the initial inoculation percentage and temperature. These two variables significantly affected ganoderic acid production and its optimum production point was 10% of initial inoculation, temperature of 25.6 °C, L: D of 4:8 and aeration rate of 0.64 vvm. Gas holdup investigation for air-water and air-fermentation media systems showed that the presence of suspended solids and aeration rate affected gas holdup. Microbial volatile organic compounds in co-culture of microorganisms can increase ganoderic acid production by Ganoderma lucidum. Conflict of interest: The authors declare no conflict of interest.