Rhamnolipid-biosurfactant permeabilizing effects on gram-positive and gram-negative bacterial strains.

The potential of biosurfactant PS to permeabilize bacterial cells of Pseudomonas aeruginosa, Escherichia coli, and Bacillus subtilis on growing (in vivo) and resting (in vitro) cells was studied. Biosurfactant was shown to have a neutral or detrimental effect on the growth of Gram-positive strains, and this was dependent on the surfactant concentration. The growth of Gram-negative strains was not influenced by the presence of biosurfactant in the media. Cell permeabilization with biosurfactant PS was shown to be more effective with B. subtilis resting cells than with Pseudomonas aeruginosa. Scanning-electron microscopy observations showed that the biosurfactant PS did not exert a disruptive action on resting cells such that it was detrimental to the effect on growing cells of B. subtilis. Low critical micelle concentrations, tender action on nongrowing cells, and neutral effects on the growth of microbial strains at low surfactant concentrations make biosurfactant PS a potential candidate for application in different industrial fields, in environmental bioremediation, and in biomedicine.

Purification and partial characterization of acid phosphatase from Candida lipolytica.

Non-specific acid phosphatase from Candida lipolytica cells was purified 111-fold by chromatography on DEAE-cellulose and gel filtration on Sephadex G-100 and Sepharose 4B. The enzyme is a glycoprotein containing 67% neutral sugars. The molecular mass of the highly purified acid phosphatase was found to be approximately 95 kDa by both SDS-PAGE and gel filtration. The pH and temperature optima were 5.8 and 55 degrees C, respectively. The enzyme was stable at pH values between 3.5 and 5.5 and at temperatures up to 60 degrees C. The purified phosphatase had a Km value of 3.64 mM for p-nitrophenyl phosphate and showed broad substrate specificity.