Abstract:
:A method is described for generating and screening variants of the beta-galactosidase from Lactobacillus delbrueckii subsp. bulgaricus sensitive to several environmental stresses, with potential application in the food industry. Chemical mutagenesis with hydroxylamine or methoxylamine was performed on the beta-galactosidase gene carried on an Escherichia coli expression vector. Mutants sensitive to cold, heat, low pH, low magnesium concentration, and the presence of urea were isolated by screening for reduced color development on beta-galactosidase indicator plates. The mutations responsible for three variant beta-galactosidases were localized, and the base substitutions were determined by DNA sequencing. The amino acid alterations associated with one low-pH-sensitive (pHs) and two urea-sensitive (Us) variants correspond to P584L (pHs1), G400S/R479Q (Us26), and G167E/E168K/E363K/V492M (Us17), respectively. Mutant pHs1 is also heat, cold, low magnesium, and urea sensitive; Us26 is also cold sensitive; and Us17 is also low-pH sensitive.
journal_name
Appl Environ Microbioljournal_title
Applied and environmental microbiologyauthors
Yoast S,Adams RM,Mainzer SE,Moon K,Palombella AL,Schmidt BFdoi
10.1128/AEM.60.4.1221-1226.1994keywords:
subject
Has Abstractpub_date
1994-04-01 00:00:00pages
1221-6issue
4eissn
0099-2240issn
1098-5336journal_volume
60pub_type
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