Cinética de crescimento e produção de biossurfactante por bacillus pumilus em meio com melaço de cana-de-açúcar

Abstract

Biosurfactants are amphipathic molecules with surface-active properties produced by biological sources, especially bacteria and fungi. Their application is driven as an alternative to petroleumderived chemical surfactants, which exhibit toxicity, low biodegradability, and environmental issues. The industrial viability of biosurfactants is limited by high production costs, particularly in downstream stages, and low yields; therefore, solutions are sought to reduce the cost of separation processes and couple biosurfactant production with renewable, low-cost substrates. The present study evaluated biosurfactant production by Bacillus pumilus using sugarcane molasses as a carbon source, through substrate characterization, evaluation of cultivation kinetic parameters, biosurfactant extraction, determination of the emulsification index, and surface tension assessment. The microorganism was isolated from sugarcane soil at the Japungu Mill, inoculated in a medium containing yeast extract, monobasic and dibasic potassium phosphate, and sugarcane molasses, and incubated in a shaker at 34°C with orbital agitation at 200 rpm. The maximum specific growth rate was 0.219 h⁻¹, with a generation time of 3,16 hours. Cell productivity was 0.005 g/L·h⁻¹, and the biomass yield per substrate was 0.041 gₓ/gₛ. Crude biosurfactant extraction was evaluated by acid precipitation and high purity ethanol precipitation in crude medium, sterilized medium, and cell-free supernatant. The highest biosurfactant concentration was obtained at 24 h of fermentation, with 3.35g/L extracted by ethanol precipitation, and the emulsification index reached its highest result at 120 h of fermentation, reaching 60% with soybean and babassu oils. The reduction in surface tension was not significant. The produced biosurfactant showed satisfactory emulsifying potential and a promising yield compared to other surfactant-producing Bacillus species