Thesis (Ph. D.)--University of Wisconsin--Madison, 1949. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves [70-72]).

Köln, Universiẗat, Diss., 2001.

Plasmid curing experiments showed that the Caprylate-Esterase (CE) gene of Lactobacillus casei subsp. casei (LLG) is located on the LLG chromosome rather than on a plasmid. The enzyme was purified and shown to be a monomer with an apparent Mr of 32,000 on sodium dodecyl sulfate-polyacrylamide gels. The N-terminal end of the CE protein was microsequenced. A synthesized 29-mer oligonucleotide deduced from L. casei codon usage and the N-terminal peptide sequence was used as probe against an LLG genomic library. Library screening yielded one positive clone (pLLG1435) with an insert of 8 kb. Southern analysis of pLLG1435 showed that the oligonucleotide probe strongly hybridized with the 1.9 kb PstI/SphI fragment found within its insert. Th fragment was subcloned and its DNA sequence was determined and found to be closely related to the phosphoribosylformylglycinamidine synthase II gene of Bacillus subtilis. The gene was completely sequenced.

No description available.

Berlin, Freie Universiẗat, Diss., 2002. / Dateiformat: zip, Datein im PDF-Format.

No description available.

No description available.

Preliminary experiments by API ZYM enzyme system showed that Lactobacillus casei (Lb. casei) subspecies contained low proteinase and high aminopeptidase and esterase-lipase activities, which are the desirable traits of microorganisms to be used as starter adjuncts in Cheddar cheese-making. Six strains of Lb. casei (ssp. casei, ssp. rhamnosus, and ssp. pseudoplantarum), selected from superior peptidase and esterase-lipase profiles, were further studied for their amino-, di-, and carboxy-peptidase activities using thirty synthetic substrates. This study revealed useful information towards improving our understanding of the peptidase profiles and probable role of Lb. casei in Cheddar cheese ripening. Although individual strains varied in their specific activities against different substrates, Lactobacillus subspecies generally exhibited high amino- and di-peptidase, relatively weak tripeptidase, but no carboxypeptidase activities. The knowledge gained from these studies helped us selecting two strains (Lb. casei ssp. casei LLG and Lb. casei ssp. rhamnosus S93) with highest amino- and di-peptidase activities for further research. In order to study their enzymatic characteristics and kinetics, aminopeptidase of these two strains were purified to homogeneity by Fast Protein Liquid Chromatography (FPLC). A single monomeric enzyme was shown to be responsible for the entire aminopeptidase activity of the cell-free extracts. This investigation provided new insights and revealed fundamental knowledge about the peptidases of Lb. casei group. In addition, new methodologies were developed for rapid enzyme purification using FPLC system, and evaluation of peptidases by API ZYM enzyme system.

The objectives of this study were (l) to screen out active proline-specific peptidases from Lactobacillus casei subspecies, (2) to study growth kinetic and enzyme production from enriched medium (MRS) and cheese whey medium, (3) to purify and characterize two active proline-specific enzymes, and (4) to investigate the action of purified enzyme on bitter tryptic digests of $ beta$-casein as well as bitter enzyme-modified cheese. Lactobacillus casei subsp. casei LLG and Lactobacillus casei subsp. rhamnosus S93 were examined for extra- and intra-cellular proline-specific peptidase activities. Both strains showed strong activity for x-prolyl dipeptidyl peptidase and proline iminopeptidase but had weak activities for prolidase, prolinase, and post proline endopeptidase. Histochemical staining of crude enzyme extract from Lactobacillus casei ssp. casei LLG with different substrates revealed a distinct protein band for x-prolyl dipeptidyl peptidase as well as for proline iminopeptidase. The growth kinetics showed that the intracellular proline-specific peptidases increased gradually at the beginning of the exponential phase and reached a maximum at the beginning of stationary phase. / Storage stability of x-prolyl dipeptidyl peptidase and proline iminopeptidase in crude extract, with and without stabilizers showed no significant loss in activity of these two enzymes at 4$ sp circ$C for 9 days without adding any stabilizers. The levels of x-prolyl dipeptidyl peptidase, proline iminopeptidase, and post proline endopeptidase activities of cells grown in whey did not vary markedly from cells grown in MRS broth. X-prolyl dipeptidyl peptidase and proline iminopeptidase were purified from crude cell-free extract of Lactobacillus casei ssp. casei LLG by Fast Protein Liquid Chromatography (FPLC) equipped with ion-exchange and gel-filtration columns. X-prolyl dipeptidyl peptidase was found to be a serine-dependent enzyme with molecular mass of 79 kDa. The pH and the temperature optima by the purified enzyme were 7.0 and 50$ sp circ$C, respectively. Proline iminopeptidase was sulfhydryl enzyme with molecular mass of 46 kDa. The maximum enzyme activity was observed at pH 7.5 and 40$ sp circ$C. This is the first report describing the purification and characterization of x-prolyl dipeptidyl peptidase and proline iminopeptidase from Lactobacillus casei to homogeneity. / The debittering of tryptic digests from $ beta$-casein by x-prolyl dipeptidyl peptidase was studied by reversed phase high performance liquid chromatography (RP-HPLC) and liquid chromatography/mass spectrometry. The results showed that two bitter peptides (f53-97 and f03-209) containing X-Pro-Y-Pro in their amino acid residues were completely hydrolyzed and many other peptides with high hydrophobicity were decreased in peak area. The addition of purified x-prolyl dipeptidyl peptidase on bitter enzyme-modified cheese (EMC) also showed that at least one bitter peptide with X-Pro-Y derived from $ alpha$-casein hydrolysis was removed.

Thesis (Master)--İzmir Institute of Technology, İzmir, 2005. / Includes bibliographical references (leaves. 56-62).