Effects of ultrasound on submerged fermentation for producing antioxidant metabolites from Botryosphaeria dothidea

Abstract

Antioxidant compounds were produced from submerged fermentation using Botryosphaeria dothidea. Sonication times (1–15 min) and agitations (0–150 rpm) applied to different fermentation phases (2–7 days) were evaluated for their effect on the broth antioxidant activity. In approximately 70% of assays performed with ultrasound, the antioxidant activity of the broth containing exocellular metabolites was higher than the control (without sonication), reaching a maximum value of 96%. The solid fraction (biomass after supernatant removal) corresponding to the best assay of antioxidant activity was submitted to extractions with water, ethanol or ethyl acetate to recover intracellular metabolites. The yields of extracts were 3.7 ± 2.6 wt %, 20.6 ± 3.9 wt % and 32.0 ± 4.2 wt % for ethyl acetate, ethanol and water, respectively. The use of ethanol could provide a larger number of compounds such as pentadecanoic acid, ergosta-5,8,22-trien-3-ol, and 1,4-diaza-2,5-dioxobicyclo [4.3.0] nonane. Both the supernatant and solid fractions revealed some bioactive compounds with promising antioxidant activity with the potential to replace some synthetic antioxidants.