Biosurfactants substrates using

MOBILISATION OF HYDROPHOBIC ORGANIC SUBSTRATES USING BIOSURFACTANTS... 

In addition to desulfurization activity, several other parameters are important in selecting the right biocatalyst for a commercial BDS application. These include solvent tolerance, substrate specificity, complete conversion to a desulfurized product (as opposed to initial consumption/removal of a sulfur substrate), catalyst stability, biosurfactant production, cell growth rate (for biocatalyst production), impact of final desulfurized oil product on separation, biocatalyst separation from oil phase (for recycle), and finally, ability to regenerate the biocatalyst. Very few studies have addressed these issues and their impact on a process in detail [155,160], even though these seem to be very important from a commercialization point of view. While parameters such as activity in solvent or oil phase and substrate specificity have been studied for biocatalysts, these have not been used as screening criteria for identifying better biocatalysts. 

Figure 5 shows some data referring to the ability of biosurfactant to emulsify kerosene produced by B. subtilis ATCC 6633 at the different substrate concentrations tested (5, 10, 20, and 40 g/L). Besides a decrease in surface tension, stabilization of hydrocarbon/water is frequently used as an indicator of surface activity. Note, however, that the quantity of biosurfactant produced should not be related to the E24 because that is an intrinsic property of the molecule. A similar behavior of the emulsifying activity in relation to the carbon source concentration and to the incubation period has been observed. The diverse initial concentrations of commercial sugar studied favor the formation of a surface-active compound, with an emulsifying activity >50% in a 48-h process. The maximum values for emulsion activity of 57.9 and 56.9% were determined for 10 and 20 g/L of substrate, respectively. It should be emphasized that there was a reduction in the E24 after a 96-h period of incubation. Carvalho et al. (36) reported similar results for cell-free fermented broth by Bacillus sp. emulsified in kerosene. 

Biosurfactants can also be employed for in-situ oil recovery either by innoculating the petroleum reservoir or by producing the compound on the surface and injecting it into the well. If the surfactant is to be produced in place, it is necessary to select the microorganisms which produce good yields of biosurfactants. Improvements in yields and fermentations which use cheaper substrates than carbohydrates are needed. 

Near-infrared spectroscopy (NIR), which is a nondestructive analytical technique, has been employed for the simultaneous prediction of the concentrations of several substrates, products, and constituents in the mixture sampled from fermentation process. In this chapter, applications of NIR to monitoring of the various fermentation processes are introduced. The fermentation processes mentioned here are wine, beer, Japanese sake, miso (soybean paste), soy sauce, rice vinegar, alcohol, lactic acid, glutamic acid, mushroom, enzymatic saccharification, biosurfactant, penicillin, and compost. The analysis of molasses, which is a raw material of fermentation, with NIR is also introduced. These studies indicate that NIR is a useful method for monitoring and control of fermentation process. 

Makkar, R. S., Cameotra, S. S. An update on the use of unconventional substrates for biosurfactant production and their new applications. Appl Microbiol. Biotechnol. 2002, 58, 428 34. 

Barros, F. F. C., Ponezi, A. N. and Pastore, G. M. (2008) Production of biosurfactant by Bacillus subtilis LB5a on a pilot scale using cassava wastewater as substrate. J. Ind. Microbiol. Biotechnol., 35, 1071-1078. 

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