Oxidative stress and morphological changes in Blakeslea trispora induced by enhanced aeration during carotene production in a bubble column reactor

Abstract

The oxidative stress and the morphological changes in Blakeslea trispora induced by enhanced aeration during carotene production in a bubble column reactor was investigated. Enhanced aeration caused changes of the morphology of microorganism from aggregates with large projected area to aggregates with small projected area. This morphological differentiation of the fungus was associated with high oxidative stress as evidenced by increase of the specific activities of superoxide dismutase (SOD) and catalase (CAT). The oxidative stress in B. trispora resulted in a significant increase in carotene production. The highest concentration of carotenes (55.0 ± 2.5 mg/g dry biomass) was obtained at aeration rate of 4 vvm. Very high oxidative stress in B. trispora caused a change in the biosynthesis of carotenes resulting an increase in γ-carotene concentration. The maximum proportion of β-carotene (91.68%), γ-carotene (44.67%), and lycopene (11.54% of total carotenes) was observed at aeration rates of 4, 5, and 5 vvm, respectively. The external addition of butylated hydroxytoluene (BHT) and hydrogen peroxide in the medium did not improve the production of carotenes.