Microbial production of biosurfactants

摘要

Biosurfactants are those chemicals which are produced by microorganisms but which have both clearly defined hydrophilic and hydrophobic groups. They occur in nature in bacteria, yeasts, and fungi, and in particular in bacteria which grow on a water-immiscible substrate, using it as a food source. By evolution these bacteria have adapted themselves to feeding on these substrates by manufacturing and using a surface active product that helps the bacteria to adsorb, emulsify, wet, or disperse or solubilise the water immiscible material. The four main types of biosurfactant are: (1) glycolipids, (2) phospholipids, (3) lipoproteins or lipopeptides, (4) polymeric. By growth of the bacterium Pseudomonas fluorescens (NCIMB 11712) on virgin olive oil, production of a glycolipid in the form of a rhamnolipid is thought to have taken place. This biosurfactant group is based on the rhamnose structure, which is a methyl pentose monosaccharide. However, rhamnolipids can also be based on the disaccharide by condensing two moles of rhamnose together. The link to the hydrophobic group is by way of an acetal group; however, the ‘lipid’ part of the molecule contains ester and carboxyl groups. Biosurfactants over the years have found a great many uses in industry, for example, (1) oil recovery, (2) oil spill clean-up, (3) textiles, (4) pharmaceuticals, (5) cosmetics. By this programme of research, it is proposed to produce a biosurfactant for use in the detergents/cleaning materials industries — with the specific aim being to produce a biosurfactant which could be used in place of chemical surfactants in a detergent formulation for use in the household.