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J Ind Microbiol Biotechnol (2008) 35:10711078 DOI 10.1007/s10295-008-0385-y
ORIGINAL PAPER
Production of biosurfactant by Bacillus subtilis LB5a on a pilot scale using cassava wastewater as substrate
Francisco Fbio Cavalcante Barros
Alexandre Nunes Ponezi Glucia Maria Pastore
Received: 11 January 2008 / Accepted: 10 June 2008 / Published online: 2 July 2008 Society for Industrial Microbiology 2008
Abstract The main characteristic of biosurfactants is their property of reducing the superWcial and interfacial tension between two immiscible liquids of diVerent polarities. The main obstacle to the application of biosurfactants is the high production costs, the use of alternative substrates being indicated to solve this problem. This work report the production of biosurfactant by Bacillus subtilis LB5a on a pilot scale using cassava wastewater as the substrate, and the study of the parameters related to its production. The cassava wastewater was heated, centrifuged and poured into a 40-liter batch pilot bioreactor adapted for simultaneous foam collection during the fermentative process. The temperature was maintained at 35 C, agitation at 150 rpm and aeration 0.38 vvm during the Wrst 12 h, and 0.63 vvm for the rest of the process. Samples of liquid fermentate were collected at regular intervals for the analysis of total carbohydrates, reducing sugars, pH, CFU/mL count and superWcial tension. The foam was centrifuged and the biosurfactant puriWed. The kinetic data of the process showed that both the microbial population, which reached a maximum after about 24 h, and the foam production of 10.6 L, peaked between 24 and 36 h, coinciding with the greatest production of biosurfactant. The yield of semi-puriWed surfactant in the foam was 2.4 g/L. The superWcial tension of the medium was reduced from 51 to 27 mN/m and the critical micellar concentration was 11 mg/L, which, in princi-
ple, characterizes it as a good tensoactive agent. As a function of its composition and productivity, cassava wastewater was identiWed as a good substrate for the production of the biosurfactant.
Keywords Cassava wastewater Bacillus subtilis Biosurfactant Lipopeptides Pilot scale
Introduction
Biosurfactants are produced by a great variety of microorganisms, such as bacteria, yeast and fungi [20, 33]. However, bacteria produce the majority of these compounds [16, 20, 28]. Strains of Bacillus subtilis are well known for their ability in producing lipopeptides with high...