Studies in carotenogenesis. 1. General conditions governing β-carotene synthesis by the fungus Phycomyces blakesleeanus Burgeff

Abstract

It has been confirmed that the major carotenoid of P. blakesleeanus is beta-carotene; small amts. of alpha-carotene are also present, but no trace of lycopene or xanthophylls was evident. On Schopfer''s (1934) medium, max. production of dry wt. and lipid occurred after 5-6 days and of beta-carotene after 5-9 days. Beta-carotene, but not dry wt. or lipid, decreased in ageing cultures. The (-) strain produced twice as much beta-carotene as the (+) strain, although lipid and dry wt. production was the same in both. Beta-carotene production was twice as great in cultures exposed to light as in those kept in the dark. When cultures exposed to light were placed in the dark they continued to produce beta-carotene at the "light" rate. Substituting either glycine, L-alanine, L-leucine, or ammonium nitrate for L-asparagine had no effect on dry wt. and little on lipid production; glycine, however, specifically stimulated beta-carotene production. Growth was poor on L-isoleucine and ammonium nitrate. In the absence of N from the medium no beta-carotene was formed, although glucose was metabolized. When the N was kept constant (0.2% L-asparagine), variation in the glucose concn. of the medium affected beta-carotene synthesis to a much greater extent than dry-wt. and lipid production, but little effect was noted when N was varied ed and glucose kept constant (2.5%). The C:N ratio appears to be less important in controlling beta-carotene production than was previously thought. Substituting either xylose, fructose or maltose for glucose had no effect on lipid or dry-wt. production; beta-carotene production was normal with maltose, but reduced with xylose or fructose. Neither lactose nor glycerol supports mycelial growth.