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Abstract
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Background and Objective: Ganoderma lucidum, with its medicinal properties, is one of the most beneficial fungi in traditional Asian medicine. This fungus's low efficiency of ganoderic acid (GA) production has limited its desirable use as a valuable secondary metabolite. Environmental stresses and elicitors, such as microbial volatile organic compounds in co-culture, can increase GA production. In order to investigate the effects of variables of culture day and volume on G. lucidum growth and GA production, Bacillus subtilis and Aspergillus niger were aerially co-cultured with G. lucidum . Material and Methods: To investigate the fungus growth and production of GA in the bubble column bioreactor, the effect of independent variables of temperature, initial inoculation, length-to-diameter ratio (L/D), and aeration was investigated by using Taguchi method. Then, the effect of co-culture of G. lucidum with B. subtilis and A. niger in the bioreactor under optimum conditions was also investigated. Results and Conclusion: Optimizing the effects of co-culture day and volume variables led to a 2.9-fold increase in the production of A compared to the control sample. Optimization of biomass production in the bioreactor showed that biomass production increases significantly by increasing the initial inoculation percentage and temperature. These two variables also significantly impacted GA production, and its optimum production point was 10% of initial inoculation, 25.6 °C, L/D of 4/8 , and aeration rate of 0.64 vvm. The gas holdup investigation for air-water and air-fermentation medium systems showed that the presence of suspended solids and aeration rate affected gas holdup. Microbial volatile organic compounds in the co-culture of microorganisms can increase GA production by G. lucidum.
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