EFFICIENT PRODUCTION OF MYCELIUM OF LENTINUS-EDODES BY A CONTINUOUS-CULTURE AND THE EFFECT OF LIGNIN ON GROWTH

In order to obtain a high yield of Lentinus edodes mycelium efficiently used as a liquid spawn for Shiitake mushroom production, a continuous culture system was investigated. The productivity of the mycelium (mg of dry weight of mycelium ml-1h-1) was 14-fold higher at a dilution rate of 0.03 h-1 than that in a batch culture. In the continuous culture, the pulpy form of the mycelium could be easily obtained either with a low dilution rate less than 0.01 h-1 or high agitation conditions of more than 400 rpm. The change in morphology to pulpy form resulted in a increase in the dry weight of the mycelium (DW). The maximum DW was 20 mg/ml at a dilution rate of 0.01 h-1. Lignin, which has been reported to accelerate the growth of L. edodes in a submerged culture, had no effect on mycelium production in the continuous culture, but promoted both the specific glucose consumption rate and maintenance energy. In addition, it was observed that lignin improved the resistance of the mycelium against shear stress. Adding 0.1% acetic acid to the feed medium and maintaining a low pH (about 4.0) in the culture allowed operation for over 70d without any microbial contamination.