Oxygen-controlled Biosurfactant Production in a Bench Scale Bioreactor

Abstract

Rhamnolipids have been pointed out as promising biosurfactants. The most studied microorganisms for the aerobic production of these molecules are the bacteria of the genus Pseudomonas. The aim of this work was to produce a rhamnolipid-type biosurfactant in a bench-scale bioreactor by one strain of Pseudomonas aeruginosa isolated from oil environments. To study the microorganism growth and production dependency on oxygen, a nondispersive oxygenation device was developed, and a programmable logic controller (PLC) was used to set the dissolved oxygen (DO) concentration. Using the data stored in a computer and the predetermined characteristics of the oxygenation device, it was possible to evaluate the oxygen uptake rate (OUR) and the specific OUR (SOUR) of this microorganism. These rates, obtained for some different DO concentrations, were then compared to the bacterial growth, to the carbon source consumption, and to the rhamnolipid and other virulence factors production. The SOUR presented an initial value of about 60.0 mgO(2)/g(DW) h. Then, when the exponential growth phase begins, there is a rise in this rate. After that, the SOUR reduces to about 20.0 mgO(2)/g(DW) h. The carbon source consumption is linear during the whole process.

Factorial Design to Optimize Biosurfactant Production byYarrowia lipolytica

“…This is consistent with the results described by Yeh et al [17] and Amaral et al [3] who have mentioned that biosurfactant production rose with the increase of agitation speed. Kronemberger et al [18] have shown that a rhamnolipid production by Pseudomonas aeruginosa depend on the specific oxygen uptake rate. The agitation speed affects the mass transfer efficiency of both oxygen molecules and medium components.…”

Physicochemical Properties of Rhamnolipid Biosurfactant from <i>Pseudomonas aeruginosa</i> PA1 to Applications in Microemulsions

“…They were then incubated at 30˚C at 170 rpm for 168 hours. Every 24 hours, 1.5 mL aliquots were taken for analysis of cell growth and rhamnolipid concentration [16] [17].…”

“…Rhamnolipid purification was carried out by extraction, using a chloroform/methanol/culture medium mixture, in the proportion of 2:1:1 and a separating funnel (see Figure 1). The organic chloroform rich phase was separated, the solvent evaporated a pasty product with a brownish color [17] was obtained.…”

Evaluation of Different Screening Methods for Biosurfactant Producers Isolated From Egyptian Fresh Water Samples Contaminated by Oil Spills Using Bacillus Subtilis and Bacillus Licheniformis

“…Important variables are carbon and nitrogen sources (Santos et al, 2002), also the use of glucose as a sole carbon source enhances the production of high yield of Biosurfactants (Fooladi et al .2013). Potential nutrient limitations and other physical and chemical parameters such as oxygen (Kronemberger et al, 2008), temperature and pH (Mukherjee et al, 2006) were considered. Bacillus licheniformis is 7 after incubation for 10 days.…”