Cloning, Expression and Characterization of a Lipase Gene from Marine Bacterium Pseudoalteromonas lipolytica SCSIO 04301

Absract A lipase gene, 1ip1233, isolated from Pseudoalteromonas lipolytica SCSIO 04301, was cloned and expressed in E. coli. The enzyme comprised 810 amino acid residues with a deduced molecular weight of 80kDa. Lip1233 was grouped into the lipase family X because it contained a highly conserved motif GHSLG. The recombinant enzyme was purified with Ni-NTA affinity chro- matography. The optimal temperature and pH value of Lip1233 were 45 ℃ and 8.0, respectively. It retained more than 70% of origi- nal activity after being incubated in pH ranging from 6.0 to 9.5 for 30min. It was stable when the temperature was below 45℃, but was unstable when the temperature was above 55℃. Most metal ions tested had no significant effect on the activity of Lip1233. Lip1233 remained more than original activity in some organic solvents at the concentration of 30% （v/v）. It retained more than 30% activity after incubated in pure organic solvents for 12 h, while in hexane the activity was nearly 100%. Additionally, Lip 1233 exhib- ited typical halotolerant characteristic as it was active under 4M NaC1. Lip1233 powder could catalyze efficiently the synthesis of fructose esters in hexane at 400C. These characteristics demonstrated that Lip1233 is applicable to elaborate food processing and organic synthesis.

Marine bacteria inhibit corrosion of steel via synergistic biomineralization

Metal corrosion often results in incalculable economic loss and significant safety hazards. Although numerous traditional methods have been used to mitigate the issue, such as coating and corrosion inhibitors, they are environmentally unfriendly and difficult to maintain. Therefore, in this study, an environmental approach was taken to protect steels from corrosion in a multi-species bacterial environment via synergistic biomineralization. The marine bacterium Pseudoalteromonas lipolytica mixed with Bacillus subtilis or Pseudomonas aeruginosa strains offered extraordinary corrosion protection for steel.The surface characterization and electrochemical tests showed that the biomineralized film generated by the mixed bacteria was more compact and protective than that induced by a single bacterium. Herein,we found that the synergistic mechanisms were rather different for the different bacterial groups. For Pseudoalteromonas lipolytica and Bacillus subtilis group, the related mechanisms were due to the increase of pH in the medium, secretion of carbonic anhydrase. As for Pseudoalteromonas lipolytica and Pseudomonas aeruginosa group, the synergistic mechanism was attributed to the inhibiting corrosive bacteria in biofilm by the growth advantage of Pseudoalteromonas lipolytica. Therefore, this study may introduce a new perspective for future use of biomineralization in a real marine environment.