PROTOP contributes to find a new outlet for ulva, a green algae which produces green tides along European coasts. The aim is to synthesize a new type of biodegradable surfactant. The bio-surfactants were initially synthesised by following a classical transesterification using fatty acid chlorides. But the results obtained were not satisfying. Therefore a new process was developed at laboratory scale. This process uses a transesterification of methyl esters with polysaccharides. The reactions were carried out without solvent. A mixture of soaps is added as catalyst. Several parameters were optimised (temperature, vacuum, raw materials, reaction time, quantity of catalyst). Treatments were also optimised: the main parameters were the kind of solvents used during extractions and the quality of the final products. The developed process produces a gelified product of grafted polysaccharides with satisfying colour and properties. The process was successfully transferred to pilot scale. The reactor used had a capacity of 8 liters. Different batches of products were produced using different kinds of methyl esters. Parameters were adjusted to the pilot scale in order to obtain the best grafting ration and the brightest colour for final products. The nature and the characterisation of the product have been studied as well as e first economical evaluation of the process. The developed process is now patented.