3.2. Effect of carbon sources
To investigate the effects of carbon sources on P. eryngii cultivation, various carbon sources such as glucose, sucrose, and lactose (2%) were added and compared. To define the control medium composition, various glucose concentrations were tested. It was found that 2% glucose showed the best results for P. eryngii cultivation (data not shown). As to the nitrogen sources, 0.1% yeast extract and 0.5% peptone were selected according to the practice in the report of Huang and Liu [17]. The results are shown in Table 2. It is obvious that the highest mycelial biomass and EPS production were obtained when glucose was used. The mycelial biomass and EPS productions of P. eryngii can reach 9.56 g/L and 59.2 mg/L, respectively. In contrast, the lowest mycelial biomass and EPS productions were observed when using lactose as a carbon source, where the mycelial biomass and EPS were observed to be 4.22 g/L and 8.3 mg/L, respectively. A similar result has been reported when employing carbon sources in Ganoderma lucidum submerged culture [26]. Accordingly, glucose was selected as the carbon source for the subsequent experiments.