OPTIMIZATION OF β-CAROTENE PRODUCTION FROM SYNTHETIC MEDIUM BY BLAKESLEA TRISPORA IN A STIRRED TANK REACTOR AND RELATIONSHIP BETWEEN MORPHOLOGICAL CHANGES AND PIGMENT FORMATION

Abstract

ABSTRACT The effect of linoleic acid, kerosene, antioxidant and a mixture of natural oils (olive oil, soybean oil, and cottonseed oil) on the production of β-carotene by Blakeslea trispora and the morphological characteristics of the fungus in a stirred tank reactor were investigated. The mixture of linoleic acid and antioxidant improved slightly the production of β-carotene, while the addition of linoleic acid, kerosene or antioxidant alone to the medium had an inhibiting effect on β-carotene production. The addition to the medium of a mixture of natural oils and antioxidant increased significantly the concentration of the pigment. B. trispora formed hyphae, zygophores and zygospores during β-carotene production. Morphology of the fungus was studied during growth in submerged culture in a stirred tank reactor under different compositions of the production medium using an image analysis system. Zygospores are the morphological forms, which are responsible for pigment production. Maximum β-carotene concentration (1500 mg/L) was obtained in culture grown in medium supplemented with 1% (w/v) each one of olive oil, soybean oil, cottonseed oil and 0.25% (w/v) of antioxidant (butylated hydroxytoluene, BHT). In this case, the morphological characteristics of B. trispora recorded showed intact hyphae, degenerated hyphae and zygospores in percentages of about 30.0%, 2.0% and 51.0% respectively in the biomass dry weight.