Produção de surfactina por Bacillus subtilis, usando borra originada no refino de óleo vegetal de soja e algodão como substrato

Abstract

Biosurfactants are active compounds, produced by microorganisms, with the ability to reduce surface tension. These compounds have the following advantages over petroleum-based surfactants: low toxicity, high biodegradability, and production from renewable sources, but they generally have a higher production cost. This cost is directly related to the cost of the substrate. On the other hand, in the industrialization of vegetable oils an oily sludge is produced. This byproduct has a low market price and is a potential substrate for fermentative bacteria. In this context, the objective of this study was to evaluate the reuse potential of this oily sludge as a substrate to produce biosurfactant surfactin. The methodology consisted of characterizing the sludge through physicochemical and chromatographic analyses, followed by inoculation and fermentation of Bacillus subtilis microorganisms in a culture medium containing different concentrations of sludge and glucose in the substrate, keeping the other variables constant, to evaluate the composition of the substrate that would result in the highest final concentration of the product. A star experimental design involving 11 fermentation trials was elaborated Then, the product was purified by centrifugation and rotary evaporation. After these steps, qualitative analyzes of the generated biosurfactant, surfactin, were carried out using droplet collapsed test, emulsification index, Fourier transform infrared spectroscopy (FTIR) and quantitative analysis using high performance liquid chromatography (HPLC). The sample with the highest concentration of surfactin was the one that contained a highest percentage of sludge than glucose: 6% and 3% of glucose, resulting in 129 mg/L of surfactin. Based on this experiment, it was a scaling simulation was carried out for industrial plant to carry out the economic viability analysis. The showed that the production can be economically viable, as it presented a profitability index of $1.42 for every $1.00 invested, with a rate of return of 49.77%. These results demonstrated that the sludge originating from the refining residue of the vegetable oil mixture of soybean and cotton can be a suitable substrate to produce surfactin by Bacillus subtilis.