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Characterization of selected microbi...

Hall, Colin Eric.

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Characterization of selected microbial lipoxygenase extracts and immobilization and stabilization of an enzymatic preparation.

紀錄類型:	書目-語言資料,印刷品 : Monograph/item
正題名/作者:	Characterization of selected microbial lipoxygenase extracts and immobilization and stabilization of an enzymatic preparation./
作者:	Hall, Colin Eric.
面頁冊數:	172 p.
附註:	Source: Dissertation Abstracts International, Volume: 68-10, Section: B, page: 6402.
Contained By:	Dissertation Abstracts International68-10B.
標題:	Agriculture, Food Science and Technology. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=NR32190
ISBN:	9780494321904

Characterization of selected microbial lipoxygenase extracts and immobilization and stabilization of an enzymatic preparation.
Hall, Colin Eric.

Characterization of selected microbial lipoxygenase extracts and immobilization and stabilization of an enzymatic preparation. - 172 p.

Source: Dissertation Abstracts International, Volume: 68-10, Section: B, page: 6402.

Thesis (Ph.D.)--McGill University (Canada), 2007.

Aspergillus niger and Penicillium candidum were grown and harvested on days 6 and 8, which corresponded to their maximal biomasses and lipoxygenase (LOX) activities. The extracts were enriched with ammonium sulfate precipitation at 30 to 70% and 20 to 60% of saturation, respectively. The LOX activity was assayed with linoleic, linolenic and arachidonic acids as substrates. Both enriched microbial LOXs demonstrated preferential substrate specificities towards free fatty acids, over acyl esters of linoleic acid. The LOXs had the highest catalytic efficiency values (ratio of V max to Km) for linolenic acid biocatalysis. Major and minor pH optima at 5.0 and 10.5 were observed for A. niger, whereas for P. candidum they were at 6.0 and 8.5. Normal phase high-performance liquid chromatography (NP-HPLC) and gas-liquid chromatography/mass spectrometry (GC/MS) characterization of end products revealed that both LOXs produced the 10-hydroperoxide of linoleic acid (10-HPOD) at 15 to 16% of total isomers detected, respectively. Chiral studies of the P. candidum LOX catalyzed hydroperoxides revealed an excess in the production of (S) stereo-isomers resultant from linoleic, linolenic and arachidonic acids bioconversion. Penicillium camemberti was grown and harvested at its maximal biomass and LOX activity. The microbial extract was ultrafiltered (30 kDa NMWCO) and KCI (7.5 ppm) was added prior to lyophilization for the stabilization of enzyme activity. The LOX and hydroperoxide lyase (HPL) activities were assayed using linoleic acid and the 10-HPOD as substrates, respectively. The post-lyophilization residual activities were 93% and 223% for LOX and HPL, respectively. The long-term storage stability (-80°C) of the extract (KCI 7.5 ppm) was &sim;100% after 8 and 4 weeks for LOX and HPL, respectively. The investigated stabilizing chemical additives included glycine, mannitol, glycerol, sucrose and polyethylene glycol. The lowest Kinactivation values were observed with glycine with 0.136 and 0.0296 for LOX and HPL, respectively. Thermostability studies indicated that 5 and 10% (w/v) mannitol and glycine effectively stabilized LOX and HPL, respectively. Immobilization of an enzymatic extract from P. camemberti containing LOX and HPL activities was performed on EupergitRTMC and EupergitRTMC250L-iminodiacetate (IDA), respectively. The free and immobilized extracts both possessed LOX activity with a pH optimum of 6.0, whereas pH 6.0 and 4.0 were the optima of the HPL activity for free and immobilized extract, respectively. Optimal LOX reaction temperatures were 30 and 55°C for the free and immobilized extract, respectively, whereas 45 and 30°C were determined for the HPL activity of the free and immobilized extract, respectively. Long-term stability (-80°C) of the immobilized extract containing LOX and HPL activity showed residual activities of 82.6 and 93.8% after 4 and 8 weeks, respectively.

ISBN: 9780494321904Subjects--Topical Terms:

1017813
Agriculture, Food Science and Technology.

Characterization of selected microbial lipoxygenase extracts and immobilization and stabilization of an enzymatic preparation.
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520 $a Aspergillus niger and Penicillium candidum were grown and harvested on days 6 and 8, which corresponded to their maximal biomasses and lipoxygenase (LOX) activities. The extracts were enriched with ammonium sulfate precipitation at 30 to 70% and 20 to 60% of saturation, respectively. The LOX activity was assayed with linoleic, linolenic and arachidonic acids as substrates. Both enriched microbial LOXs demonstrated preferential substrate specificities towards free fatty acids, over acyl esters of linoleic acid. The LOXs had the highest catalytic efficiency values (ratio of V max to Km) for linolenic acid biocatalysis. Major and minor pH optima at 5.0 and 10.5 were observed for A. niger, whereas for P. candidum they were at 6.0 and 8.5. Normal phase high-performance liquid chromatography (NP-HPLC) and gas-liquid chromatography/mass spectrometry (GC/MS) characterization of end products revealed that both LOXs produced the 10-hydroperoxide of linoleic acid (10-HPOD) at 15 to 16% of total isomers detected, respectively. Chiral studies of the P. candidum LOX catalyzed hydroperoxides revealed an excess in the production of (S) stereo-isomers resultant from linoleic, linolenic and arachidonic acids bioconversion. Penicillium camemberti was grown and harvested at its maximal biomass and LOX activity. The microbial extract was ultrafiltered (30 kDa NMWCO) and KCI (7.5 ppm) was added prior to lyophilization for the stabilization of enzyme activity. The LOX and hydroperoxide lyase (HPL) activities were assayed using linoleic acid and the 10-HPOD as substrates, respectively. The post-lyophilization residual activities were 93% and 223% for LOX and HPL, respectively. The long-term storage stability (-80°C) of the extract (KCI 7.5 ppm) was &sim;100% after 8 and 4 weeks for LOX and HPL, respectively. The investigated stabilizing chemical additives included glycine, mannitol, glycerol, sucrose and polyethylene glycol. The lowest Kinactivation values were observed with glycine with 0.136 and 0.0296 for LOX and HPL, respectively. Thermostability studies indicated that 5 and 10% (w/v) mannitol and glycine effectively stabilized LOX and HPL, respectively. Immobilization of an enzymatic extract from P. camemberti containing LOX and HPL activities was performed on EupergitRTMC and EupergitRTMC250L-iminodiacetate (IDA), respectively. The free and immobilized extracts both possessed LOX activity with a pH optimum of 6.0, whereas pH 6.0 and 4.0 were the optima of the HPL activity for free and immobilized extract, respectively. Optimal LOX reaction temperatures were 30 and 55°C for the free and immobilized extract, respectively, whereas 45 and 30°C were determined for the HPL activity of the free and immobilized extract, respectively. Long-term stability (-80°C) of the immobilized extract containing LOX and HPL activity showed residual activities of 82.6 and 93.8% after 4 and 8 weeks, respectively.
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