Resumo

Modern society produces high quantity of waste materials through activity related to industries, forestry, agriculture and municipalities. Their high content of fats, oils and other nutrients make them interesting and cheap raw subtrtates for industries involved in useful metabolite production as biosurfactants. Biosurfactants are microbial molecules with hydrophobic and hydrophilic portions that are distributed preferentially at the interface between fluid phases. These properties give them the ability to reduce surface tension and promote the formation of microemulsions for the solubilization of hydrocarbons. This work was aimed for biosurfactant production by Serratia marcescens UCP/WFCC 1549 using agro-industrial wastes. The culture media used for microbial growth and biosurfactant production were composed by cassava wastewater (6%) and soybean or corn waste frying oil (7.5%), respectively. The fermentation experiments were carried out using three 250 mL Erlenmeyer flasks containing 100 mL of production medium, in each case (medium with soybean or corn waste frying oil) inoculated with 1 mL of pre-inoculum (107 cells/mL) from Luria Bertani broth. The flasks were maintained for 72 h, under orbital agitation (150 rpm) at 28 °C. After this period, aliquots were used to measure surface tension on the cell-free broth obtained centrifuging the cultures at 10 000g for 15 min. The surface tension was determined using a Tensiometer model Sigma 70 (KSV Instruments LTD - Finland) using the Du Nouy ring method at room temperature. The results showed the excellent reduction in surface tension of the water from 70 to 27.2 mN/m and 26.3 mN/m, in medium containing cassava wastewater and soybean or corn waste frying oils, respectively. S. marcescens UCP/WFCC 1549 demonstrated its potential as biosurfactant producer using these residues as substrates. The use of agro-industrial wastes is advantageous because contributes to environmental pollution reduction and allows them aggregate market value.