Optimization of the cordycepin production by cordyceps militaris in submerged culture

Abstract
Cordyceps militaris is a famous strain that produces a variety of bioactive compounds such as polysaccharides and nucleosides which have been used as medicine in traditional Chinese medicine (TCM). Cordycepin is a nucleoside produced by Cordyceps militaris. It shows high anticancer and antioxidant activities in vitro and in vivo bioassays. Therefore, cordycepin as a potential anticancer compound, is a good replacement for chemical-based drugs used in chemotherapy. In this work, optimization process was carried out to maximize cordycepin production in both shake flask and bioreactor using mushroom C. militaris DSM 23612 strain. For shake flask study, the medium composition was optimized using both one factor at a time (OFAT) and Response Surface Methodology (RSM) methods. The optimal medium for cordycepin production using OFAT was composed of (in gL-1): glucose (40.0), potassium nitrate (15.0), K2HPO4 (0.5), KH2PO4 (0.5), MgSO4.7H2O (0.5), and FeSO4.7H2O (3.0). In addition, the optimal medium composition by statistical optimization method was composed of (in gL-1): glucose (55.0), potassium nitrate (17.8), K2HPO4 (0.5), KH2PO4 (0.5), MgSO4.7H2O (0.5), and FeSO4.7H2O (2.5). The cordycepin at 318.51±1.26 mgL-1 was obtained using OFAT-optimized medium. The maximal cordycepin production (461.73 ± 2.72 mgL-1) was achieved using RSM optimized medium, which was approximately 1.44-fold higher than the one attained using OFAT optimized medium. Next, the process was optimized in 5-L stirred tank bioreactor. The amount of cordycepin produced were 446.1 mgL-1 and 381.82 mgL-1 in bioreactor without and with pH control, respectively. The aeration rate of 1.5 v/v/min was the best for cordycepin production. Furthermore, a series of fed-batch cultivations were carried out to determine the factors that limit the cell growth and cordycepin production. A combination of constant monocarbon (glucose) feeding with dissolved oxygen control was found to be the best strategy for maximum cordycepin production (814.19 mgL-1). In addition, the optimal extraction condition was using solvent-solvent mixture (v/v) containing hot water (23%), ethanol (30%), methanol (25%) and ethyl acetate (22%) with extraction temperature at 35 °C for 90 min. The extracted cordycepin has the purity of 81%. The significant findings from this study were successful utilization of potassium nitrate as inexpensive nitrogen source and scalable solvent based extraction technique in producing high amount of cordycepin
Description
Thesis (PhD. (Bioprocess Engineering))
Keywords
Antineoplastic agents—Research, Bioactive compounds—Research, Cordyceps
Citation