Improvement of citric acid-producing fungi by alteration of metabolic regulation = Taisha seigyo kiko no kaihen ni yoru kuen-san seisan shijokin no kairyoImprovement of citric acid-producing fungi by alteration of metabolic regulation = Taisha seigyo kiko no kaihen ni yoru kuen-san seisan shijokin no kairyo 代謝制御機構の改変によるクエン酸生産糸状菌の改良