Glucose sophorolipid production

To the compounds shown above, an amount of lipophilic substrate is added either wholly, stepwise or continuously. Additional glucose is usually added when its concentration drops below 1%. The pH stabilizes to around 3-3.5 after the growth phase, so very little, if any, pH correction is needed. Some researchers do prefer to keep the pH at 3.5. The hydroxylation of the lipophilic substrate requires molecular oxygen therefore the medium needs be aerated sufficiently in order to achieve proper production levels. In order for sophorolipid production to commence, the carbon-to-nitrogen ratio must be sufficiently high. Production therefore occurs almost exclusively in the stationary... 

Sophorolipid is a glycolipid, ie it is composed of carbohydrate and lipid. It therefore contains moieties of widely different oxidation levels and its synthesis from single demand carbon sources has a high ATP demand. However, the demand for ATP is reduced if a mixture of glucose and C-18 alkane is used. If glucose and fatty add is used the ATP demand is reduced further and relatively high spedfic production rates can be achieved. 

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. 

A typical medium for the production of sophorolipids will consist of a nitrogen source, small amounts of various minerals and over 10% of glucose as the main source of energy and carbon. For the nitrogen source, yeast extract is mainly used on a laboratory scale and processed waste products such as com steep liquor are used on an industrial scale. Small amounts of mineral nitrogen may be used as a supplement. An example of such a medium is shown in Table 11.1, according to Lang etal. [14]. 

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