Temporal changes of cell growth pattern and intracellular content of $eta$-D-glucans were investigated with off-gas data in Agaricus blazei culture where glucose was intermittently fed. It was observed that the time point of carbon source depletion coincided with the point of sudden drop in the carbon dioxide evolution rate (CER), and that the sole supplementation of glucose was not enough to maintain active cell growth and glucan content. On the other hand, when yeast extract, a typical nitrogen source, was supplemented together with glucose when the CER suddenly dropped because of carbon source depletion, an active cell growth could be maintained until the end of the culture and the glucan content did not decrease with culture time, significantly enhancing glucan productivity.