Screening And Properties Research Of The Esterase From Marine Microorganisms

Esterase (EC3.1.1.1) is a generic terms of all enzymes which are able to catalyze and h-ydrolyze carboxylic ester. Microbial esterase has broad application prospects on biotransfor-mation and kinetic resolution. There is a large number of microorganisms producing esterase in ocean environment. Because of their special growth environment, they have more excellent enzymology characteristics.In order to supply some evdiences for further study of marine esterase, structure and pro-perties of esterase was focused. Bacteria producing esterase was screened from sea water and mud, and the conditions of bacillus producing esterase and properties of esterase were studied in this research.Culture medium was selected containing tributyrin, olive oil and the indicator Rhodamine B, as a specific substrate. Through primary and secondary screening, a higher esterase activity strain was obtained and named LJ-7. The strain was identified as Bacillus, Bacillus licheniformis according to physiological and biochemical identification. Growth curve results showed the logarithmicphase of Bacillus licheniformis LJ-7was18-32h and entered in exponential phase after32h.Optimize culture medium and fermentation conditions of bacillus licheniformis LJ-7we-re as follows:Compositions of medium were (w/v):beef extract3.0, Pepton10.0, NaCI10.0, Maltose5.0; Under the condition of inoculation2%, temperature30℃, initial pH5.5,170r/min, after fermentation of45h, the enzyme activity of bacillus licheniformis was35.97U/mL.According to grading precipitation with saturated ammonium sulfate, enrichment by dia-lysis bags, DEAE52cellulose ion exchange column elution, collection the peak by SDS-PA GE, esterase was purified and the molecular weight of esterase from Bacillus licheniformis LJ-7was23.6kDa.Enzymatic properties of Bacillus licheniformis esterase were as follows:(1) The optimu-m temperature of enzyme was40℃. Thermal stability was that the esterase activity was83.20%,71.80%,60.90%and49.80%respectively under45℃、50℃、55℃and60℃for 30min.(2) Esterase showed better stability in alkaline condition than in acidity condition, es-pecially under pH6.2～8.0, and when the pH was8.0, the esterase had the highist activity.(3) K+and Mn2+inhibited esterase activity while Cu2+and Fe2+promoted it.