∗ Utilization of Free and Acetylated l- and dl-Tryptophane by Oidium Lactis

Abstract

It has long been known that Oidium lactis is able to utilize the nitrogen of several natural amino acids for growth when such acids serve as the sole source of nitrogen. Under such circumstances, l-tryptophane is converted into l-indolelactic acid. 1 In conjunction. with a series of studies on tryptophane metabolism recorded elsewhere, in which Oidium lactis was used to synthesize indolelactic acid, 2 it seemed of interest to compare the availability of l- and dl-tryptophane and acetyl-l- and acetyl-dl-tryptophane as sources of nitrogen for the growth of this mold.

Accordingly, 8 liters of a synthetic medium containing 80.0 gm. invert sugar, 8.00 gm. K₂HPO₄, 0.800 gm. MgSO₄, and traces of NaCl and FeCl₃ were prepared and divided equally among eight 2800 cc. culture flasks. To each of one pair of the flasks were added 2.000 gm. of l-tryptophane; to each of a second pair, 2.000 gm. of dl-tryptophane; to each of a third pair, 2.412 gm. of acetyl-l-tryptophane; and to each of the fourth pair, 2.412 gm. of acetyl-dl-tryptophane. The flasks were fitted with cotton plugs and sterilized. A 10 cc. aliquot was withdrawn from each for initial N analysis (by micro-Kjeldahl). To each flask were then added equal volumes of a suspension of Oidium lactis (American Type Culture Collection, No. 4798). The culture media were incubated at 20°C. for 4 weeks, at the end of which time they were sterilized. N determinations were again made on aliquots of each of the mycelium-free filtrates. The indolelactic acid was isolated from the l- and dl-tryptophane media according to the method of Ehrlich and Jacobsen 1 and the tryptophane was obtained from the residues by isolation through the mercuric sulfate salt, as in its preparation from protein. 3 No significant changes in N content having been observed in the acetyl-tryptophane media, no attempts were made to isolate indolelactic acid.