Browsing by Author "Zheng, Jiong"

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    Purification, crystallization and cloning of tributyrin esterase from Lactococcus : a thesis presented in partial filfillment of the requirements for the degree of Master of Technology in Biotechnology in the Institute of Molecular Biosciences at Massey University, New Zealand
    (Massey University, 1998) Zheng, Jiong
    Tributyrin esterase is an enzyme that has been isolated and purified from lactococcal starter strain by research staff at the New Zealand Dairy Research Institute. It has been shown to play an important role in production and control of flavour development during cheese ripening, but little is known about its biochemical characteristics. New studies on tributyrin esterase have been initiated, with the aim of carrying out a three dimensional structure determination to completely understand the molecular basis and the nature of its in vivo activity. This thesis is divided into three main parts. In the first part, the purification of tributyrin esterase from a genetically modified strain Lc. lactis subsp. cremoris B1079 is described. The procedure investigated for optimization of the protocol and a partial study of factors affecting tributyrin esterase activity are described. In the second part, crystallization trials for tributyrin esterase are described. Several crystals were obtained, with the best ordered crystals being grown from 2.6M ammonium sulfate, these have been shown to diffract to 3.0 Å, and belong to the space group C222 with cell dimensions a=76Å, b=178Å c=179Å. In the third part, the lipase gene was ligated into 4.75kbp expression vector proEX, which contains a his-tag sequence upstream of the multiple cloning site. The ligation reaction mixture was transformed into competent E.coli DH5α cells. This should allow the expression of tributyrin esterase in E.coli and eventually provide a great yield of protein and make purification easier.