Simultaneous Biodegradation of Phenol and n-Hexadecane by Cryogel Immobilized Biosurfactant Producing Strain Rhodococcus wratislawiensis BN38.

The capability of the biosurfactant-producing strain Rhodococcus wratislawiensis BN38 to mineralize both aromatic and aliphatic xenobiotics was proved. During semicontinuous cultivation 11 g/l phenol was completely degraded within 22 cycles by Rhodococcus free cells. Immobilization in a cryogel matrix was performed for the first time to enhance the biodegradation at multiple use. A stable simultaneous hydrocarbon biodegradation was achieved until the total depletion of 20 g/l phenol and 20 g/l n-hexadecane (40 cycles). The alkanotrophic strain R. wratislawiensis BN38 preferably degraded hexadecane rather than phenol. SEM revealed well preserved cells entrapped in the heterogeneous super-macroporous structure of the cryogel which allowed unhindered mass transfer of xenobiotics. The immobilized strain can be used in real conditions for the treatment of contaminated industrial waste water.

Beta-aspartylpeptides as substrates of L-asparaginases from Escherichia coli and Erwinia chrysanthemi.

L-Asparaginase is known to catalyze the hydrolysis of L-asparagine to L-aspartic and ammonia, but little is known about its action on peptides. When we incubated L-asparaginases purified either from Escherichia coli or Erwinia chrysanthemi - commonly used as chemotherapeutic agents because of their antitumour activity - with eight small beta-aspartylpeptides such as beta-aspartylserineamide, beta-aspartylalanineamide, beta-aspartylglycineamide and beta-aspartylglycine, we found that both L-asparaginases could catalyze the hydrolysis of five of them yielding L-aspartic acid and amino acids or peptides. Our data show that L-asparaginases can hydrolyze beta-aspartylpeptides and suggest that L-asparaginase therapy may affect the metabolism of beta-aspartylpeptides present in human body.