PROTEIN HYPERSECRETORY TRICHODERMA-REESEI MUTANT RUT C-30 DISPLAYS INCREASED ETHANOL AND POLYENE RESISTANCE

Addition of low amounts of ethanol (0.5-2%, v/v) or of polyene antibio tics (nystatine, amphotericin B 0.5-2 mg l-1, respectively) to culture s of T. reesei QM 9414 in the early phase of mycelial growth, arrested the secretion of three cellulases (cellobiohydrolase I and II, endogl ucanase I) as well as of a xylanase. Enzyme formation by the enzyme-hy perproducing strain T reesei RUT C-30, in contrast, was less sensitive to these agents. By the use of[U-C-14]-L-valine addition, this blocka ge of enzyme formation was shown to be due to a general inhibition of protein secretion by ethanol. Ethanol and amphotericin B also arrested the formation of intracellular precursers of cellobiohydrolase I, and the formation of the cbh1-mRNA, hence proving that blockage occurs at a pre-translational level. The higher sensitivity of the lower produc ing mutant T reesei QM 9414 correlated with an increased synthesis of a 36 kDa stress protein. The data are discussed with respect to a plas ma membrane located resistance to ethanol or polyenes in the hyperprod ucing mutant T reesei RUT C-30, probably caused by the use of bile aci ds as colony restrictor in the course of mutant selection.