What are biosurfactants

• Microbial surface active agents.• Capable of changing surface active

phenomena as – • lowering of surface & interfacial

tensions,• Other functions.

Characteristics of biosurfactants

• Biodegradability.• Low toxicity.• Biocompatibility.• Cheaper raw materials.• Production economics.• Application in environmental control.• Specificity• Effectiveness at extreme conditions.

Classification of biosurfactants• According to- 1. structure 2. source

. According to source- Enzyme synthesized - Microbial synthesized

Biosurfactants produced by prokaryotic cells

• Rhamnose lipids• Produced by carbon sources-glycerol,ethanol,fructose,glucose,n-

alkanes,vegetable oils• wastes –mollases• pollutants- phenanthrene• waste vehicle oil

• Lowest interfacial tension – 0.2 mN/m• Good emulsifiers• Used for removal of copper and zinc

Other lipids

• Trehalose lipids.• Glucose lipids.• Sucrose lipids.• Ornithin containing lipids.• Surfactin• Pentasaccharide lipids.• Exopolysaccharide bioemulsifiers• High affinity for oil water interface• Emulsan-Acinetobacter calcoaeticus RAG-1

• Other biosurfactants.

Biosurfactants by Eukaryotic cells

• Yeast biosurfactants• 1. Sophorose lipids- C. bombicola,C.

apicola,C.gropengiesseri• Linked by lactonic bond to sat or unsat FA• Sources –palmoil,rapeseed,linseed,safflower,soybean,animal fats yielding

higher than 340g/litre.• Novel sophorose lipids from C. bombicola using dodecanols.

• 2. Mannosylerythrotol lipids• C.antartica , total lipids reached 40g/litre• Reduces surface tension against n-tetradecane to 28mN/m.

Enzyme synthesized biosurfactants

• Advantages- low energy requirement,minimal thrmal degradation,high biodegradability,high regioselectivity.

• Different routes for enzymatic synthesis of glycolipids• Glycolipid synthesis via sugar acetals, alkyl glycosides and glycosidase

catalysis.• High production cost but low recovery cost.

• Disadvantage• High enzyme costs, difficulty in solubilizing hydrophilic and hydrophobic

substrates.

Biosurfactant production methods

• 1. Cell growth associated production.• Optimization of medium composition, environmental factors, reagents

addition for change in cell wall permeability, or detachment of cellwall bounded biosurfactants or induction by using lipophilic substrates.

• 2. Production by Growing cells under growth limiting conditions.

• Production under N limitation of N, multivalent cations,growth limiting environmental conditions.

• 3. Production by resting cells• Production by resting free cells, resting immobilized cells, immobilized

cells with product removal• Growing in prescence of precursors.

Media formulation

• Carbon source :• N alkane or vegetable oil –Psuedomonas in rhamnolipid

production.

• Mixture of CH & hydrocarbons-Candida in sophorose lipids

• Whey concentrate & rapeseed oil –Candida bombicola.

• Nitrogen source:• Nitrogen exhausion- increased rhamnolipid & Sophorose production.• C/N ratio- controls production• Nitrate – maximum production in Rhodococcus sp

• Phosphate source :• Phosphate reduction caused increased production.

• Iron and manganese salts :• Increased surfactin yield in B. subtilis.

• Experimental conditions-pH , temperature, DO, ionic strength• Oxygen limited conditions 3 fold higher yield by Bacillus & psuedomonas.

• Inexpensive substrate• P.aeruginosa GS3 rhamnolipid production- molasses as C source and corn

steep liquor as N source.

Fermentation

• Batch /continuous fermentations• Air lift fermentors, aqueous 2 phase

fermentors• Solid state fermentations • 2 stage fed batch fermentors

Product recovery

• Depends on ionic charge and solubility in water, whether extracellular or cell bound.

• Solvent extraction commonly used for purification using chloroform, methanol, acetic acid, ether , ethylacetate etc.

• Precipitation, Organic extraction, adsorption chromatography used• Concentration technique- water soluble surfactant• Methanol precipitation- biosurfactant from Nocardia sp• Acidification and chloroform/methanol extraction rhamnolipids by

Pseudomonas sp.• Ultracentrifugation and isoelectric precipitation – surfactin by B. subtilis.• Foam fractionation- lichenysin production by B. licheniformis.

Applications• Metals industry• Paper industry• Paint and protective coating• Petroleum products• Textiles• Building and construction• Agriculture• Plastics• Food and beverages• Industrial cleaning• Cosmetics and pharmaceuticals• Pollution control.