MICROBIAL-PRODUCTION OF SQUALENE BY A NICOTINIC ACID-RESISTANT MUTANTDERIVED FROM FUSARIUM SP NO 5-128B

A nicotinic acid-resistant mutant, designated NA201, was obtained from Fusarium sp. no. 5-128B by treatment with ultraviolet light. This mut ant strain could grow in the presence of up to 500 mM nicotinic acid i n the culture medium, although the parent strain could not grow at con centrations of nicotinic acid above 200 mM. The NA201 strain exhibited morphological mutations, neither forming aerial hyphae nor secreting a red-brown pigment. However, it retained the resistance to kabicidin at 25 mg l(-1) of the parent strain. The mutant NA201 cells contained high levels of squalene and low levels of ergosterol, about 53 times h igher and five to six times lower, respectively, than those of the par ent strain under standard culture conditions. The volumetric oxygen tr ansfer coefficient (Kd) affected the level of squalene in the mutant c ells. The Kd for the maximum production of squalene by the mutant was 24 mmol O-2 l(-1)h(-1)atm(-1) and the level of squalene in the mutant cells was 26 mg (g cell)(-1) on a dry weight basis. The greatest accum ulation of squalene by the NA201 strain, corresponding to 323 mg per l iter of culture medium and 35 mg (g cell)(-1) on a dry weight basis, w as achieved in a culture in which the Kd was changed from a high to a low value on the third day, with the simultaneous addition of 3% gluco se (w/v).