Abstract:
:Different whole-cell immobilization methods and conditions were tested for the delta 1-dehydrogenation of 6-alpha-methyl-hydrocortisone-21-acetate with Arthrobacter simplex cells, in n-decane-1-ol and chloroform. Among the entrapment methods, polyurethane foams gave the best productivity of n-decane-1-ol, but could not be used in chloroform. Partition and diffusional barriers appeared to be the factors limiting productivity in entrapped-cell systems. The coentrapment of enzyme-stabilizing (glycerol, sucrose, sodium sulfate, monosodium glutamate) or hydrophobic additives did not significantly improve dehydrogenation rates in chloroform, although in some cases higher activities resulted in n-decane-1-ol. Dehydration of kappa-carrageenan-immobilized cells lowered the productivity in both solvents. The use of cell adsorption methods on silica-based carriers produced biocatalysts that in some cases were more active in chloroform than the entrapped cells. However, the surface-attached cells appeared to be more sensitive to solvent toxicity, more hydrophilic supports generally giving higher dehydrogenation rates. The estimated partition coefficients for the substrate between several of the tested supports and the two solvents are also presented. High partition ratios followed high measured activities in entrapment matrices but not in Celite (cell adsorption matrix). Activities in chloroform were always very low (less than 1 mumol product per hour and gram of cell dry weight). Polyurethane entrapment with n-decane-1-ol as a reaction medium was the most promising system, with measured dehydrogenation rates up to 40 times higher.
journal_name
Enzyme Microb Technoljournal_title
Enzyme and microbial technologyauthors
Pinheiro HM,Cabral JMdoi
10.1016/0141-0229(92)90036-nkeywords:
subject
Has Abstractpub_date
1992-08-01 00:00:00pages
619-24issue
8eissn
0141-0229issn
1879-0909pii
0141-0229(92)90036-Njournal_volume
14pub_type
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journal_title:Enzyme and microbial technology
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journal_title:Enzyme and microbial technology
pub_type: 杂志文章
doi:10.1016/0141-0229(92)90144-d
更新日期:1992-06-01 00:00:00
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journal_title:Enzyme and microbial technology
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journal_title:Enzyme and microbial technology
pub_type: 杂志文章
doi:10.1016/j.enzmictec.2016.09.008
更新日期:2016-12-01 00:00:00
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journal_title:Enzyme and microbial technology
pub_type: 杂志文章
doi:10.1016/j.enzmictec.2015.08.004
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journal_title:Enzyme and microbial technology
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journal_title:Enzyme and microbial technology
pub_type: 杂志文章
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journal_title:Enzyme and microbial technology
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journal_title:Enzyme and microbial technology
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journal_title:Enzyme and microbial technology
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journal_title:Enzyme and microbial technology
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journal_title:Enzyme and microbial technology
pub_type: 杂志文章
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journal_title:Enzyme and microbial technology
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journal_title:Enzyme and microbial technology
pub_type: 杂志文章
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journal_title:Enzyme and microbial technology
pub_type: 杂志文章
doi:10.1016/j.enzmictec.2014.10.001
更新日期:2015-01-01 00:00:00
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journal_title:Enzyme and microbial technology
pub_type: 杂志文章
doi:10.1016/j.enzmictec.2013.09.003
更新日期:2014-02-05 00:00:00
abstract::Two GH43 β-xylosidases, RS223-BX from a rice straw metagenomic library, and BoXA from Bacteroides ovatus, that share similar amino acid sequences (81% identical) and 19 of 20 active-site residues, were compared by using site-directed mutagenesis of Asp and His residues implicated in metal binding. Thus, RS223-BX is st...
journal_title:Enzyme and microbial technology
pub_type: 杂志文章
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更新日期:2018-07-01 00:00:00