Waste biomass surfactants from

Flor Yunuen Garcia-Becerra, David Grant Allen and Edgar Joel Acosta 

Department of Chemical Engineering Applied Chemistry, University of Toronto, Canada 

As has been established in other chapters of this book, the reasons behind the search for bio-based alternatives to petroleum-based surfactants can be summarized in one word - sustainability. However, there are different ways to produce bio-based surfactants, all of which have different degrees of sustainability. As an example, soaps - alkaline salts of fatty acids - can be considered bio-based surfactants, as they are derived from the saponification of triglycerides obtained from plants and animals. Methyl ester sulfonates are obtained from fatty acid methyl esters (FAMEs) which in turn are also obtained from triglycerides found in plants and animal tissues. Lecithin, lysolectihins and other phospholipids can also be extracted from plant and animal tissue. As will be explained in the next sections, bio-based surfactants can also be secreted by microbial cultures fed with specific substrates. 

In all the above examples, there is no question about the bio-based origin of the surfactant, its biocompatibility and its ability to quickly biodegrade. However, all these attributes are necessary but not sufficient to answer the question of sustainability. Currently there are questions being raised about the sustainability of growing crops of palm oil in southeast Asia which are currently used as feedstock for soaps and other biobased surfactants. Some of the issues being considered are reduction in biodiversity, deforestation, impact of fertilizers and pesticides, and reduction in the natural habitat for numerous species [1], With respect to the production of biosurfactants by microorganisms (e.g. rhanmoUpids and sophorolipids), valuable carbon sources such as glucose are often used. These carbon sources are expensive, and are also a food source for animals and humans. 

Surfactant from Renewable Resources Edited by Mikael Kjellin and Ingeg d Johansson ( ) 2010 John TOley Sons, Ltd 

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It is important to recall that the research into bio-based surfactants extracted by chemical methods from waste biomass is still in its early days. As such, the production technology that will be described in the next section is still quite close to laboratory protocols and not industrial processes. As will be described in more detail, the quality of these surfactants is inferior to the quality of the biosurfactants produced (higher CMC, higher surface tension after CMC). However, the potential for high throughput, abundance of the biomass and the current economics of wastewater biosolid handling make this an interesting alternative for some applications that will be described later in this chapter. 

Figure 9.10 Surface tension-surfactant concentration curves for alkaline extracts from waste biomass. The data from Garcia-Becerra was obtained in an electrolyte solution containing 1 g NaCI/IOOml. The sodium dodecyl benzene sulfonate data (SDBS) was obtained at a pH of 6 [43, 661...

Surfactants Obtained from Biological TYansformation of Waste Biomass... 

The efforts in reducing the production costs for biosurfactants have taken three basic routes the use of less expensive carbon sources, the genetic modification of strains to improve surfactant yield and the improvement in the method of separation of the surfactant from the cell culture [19], We will describe in more detail the efforts made in using waste biomass as the source of carbon and nutrients for the synthesis of biosurfactants. 

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