Influence of toluene and salinity on biosurfactant production by Bacillus sp.: scale up from flasks to a bench-scale bioreactor

Ellen Cristina Souza,Thereza Christina Vessoni-Penna,José Manuel Domínguez,Saleh Al Arni,Ricardo Pinheiro De Souza Oliveira,Attilio Converti

doi:10.1590/0104-6632.20170342s20150787

Abstract

ABSTRACT To select the best biosurfactant producer, Pseudomonas putida, Bacillus megatherium, Bacillus licheniformis and Bacillus subtilis were cultured in flasks on media with different salinity [low salinity (LS), Bushnell-Haas (BH) and artificial sea water (SW) media] supplemented or not with toluene as a model pollutant. Toluene inhibited the growth of all microorganisms and stimulated the biosurfactant production. B. subtilis exhibited the best performance, being able to lower the surface tension (ST) in the LS medium to 65.5 mN/min in the absence of toluene, and to 46.5 mN/min in the BH medium in the presence of toluene, corresponding to ST reductions of 13.0 and 27.5 mN/m, respectively. Scaling up the process to a bench-scale fermentor, the best results were obtained in the LS medium, where B. subtilis was able to reduce the toluene concentration from 26.0 to 4.3 g/L within 12 h and ST by 17.2 mN/m within 18 h. The results of this study point out that B. subtilis is an interesting biosurfactant producer, which could be used in the bioremediation of toluene-contaminated water.

Highlights

Concerns related to the potential contamination of soil and water by oil and its derivatives have been gradually increasing
Bacteria were grown in media with different salinities either with or without toluene, while P. putida
Among the microorganisms belonging to the Bacillus genus used in this work, B. subtilis proved to be the most effective producer of biosurfactant in the selected media, namely low saline medium, BH medium and a medium simulating seawater composition

Summary

Introduction

Concerns related to the potential contamination of soil and water by oil and its derivatives have been gradually increasing. The main sources of contamination are: a) unintended spill during the transportation of fuels by ships and trucks; b) leaking from underground storage tanks such as those used in gas stations, which are subject to corrosion; c) oil extraction and processing operations; and d) inadequate disposal of oily wastes from industries that use oil derivatives to produce plastics, solvents, pharmaceuticals, cosmetics, etc. (Du et al, 2014; Kavitha et al, 2014) Residues produced by such activities are composed of oils, fats, organic compounds and metals. Oliveira of these compounds are considered to be extremely polluting because, besides being toxic, some of them have carcinogenic and mutagenic potential for human beings (Janbandhu and Fulekar, 2011)

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Conclusion