Isolation of microorganisms from vinasse and black liquor and screening of potential biosurfactant producers

RIVERO, MARIANO; DOLORES GUTIÉRREZ CACCIABUE; RAJAL, VERONICA BEATRIZ; IRAZUSTA, VERÓNICA PATRICIA

Conferencia; Congreso Conjunto de la Sociedad Argentina de Investigación Bioquímica (SAIB) y la Asociación Civil de Microbiología General (SAMIGE); 2020

Biosurfactants are compounds produced by microorganisms that have the ability to reduce the interfacial tension. These biomolecules have advantages over the synthetic ones: they are biodegradable and do not accumulate in the environment, they show less toxicity and have appropriate physical and chemical properties for different applications. The disadvantage is their higher production costs. The use of economic substrates, such as industrial by-products which carbon sources in its composition, could be a feasible option.The aims of this work were: (1) to isolate microorganisms capable of growing in media prepared with two substrates: black liquor (alkaline) and vinasse (acid), by-products of paper and alcohol industries, respectively, and (2) to evaluate the potential of the isolated strains to produce biosurfactants, by measuring the surface tension (TS) with a modified pendant drop method.A first isolation was carried out in prepared solid media (aqueous solution, substrate and agar), from which a total of 39 strains were obtained (19 from vinasse and 20 from black liquor). Then two consecutive screening experiments were carried out. First, tubes with 15 ml of medium (nutrient broth and 5% of the corresponding substrate) were prepared and inoculated with each of the 39 strains. For the second experiment, culture media with 5% and 20% proportions of each substrate were prepared and inoculated with selected strains from the first test, with an initial optical density established (OD600nm = 0.1). Both tests were performed in duplicate and with controls (sterile media without microorganisms). All tubes were incubated at 35 °C and 200 rpm. In the second trial, OD values were measured.The biosurfactant production was evaluated through the TS with the pendant drop method, performing simultaneous measurements with a multi-needle device developed for this purpose.Fifteen of the 39 strains evaluated, showed a TS decrease compared to the control: 5 acidophilic (a1, a5, a6, a14 and a15) and 10 alkaliphilic (b1, b2, b3, b5, b6, b8, b10, b14, b17 and b20). In addition, 3 acidophilic (a1, a5 and a6) and 3 alkaliphilic strains (b1, b2 and b17), were able to appreciably decrease the TS compared to the control (p